Automatic Transmission - 6t70 - Diagnostic Information and Procedures Buick LaCrosse II

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

The transmission control module (TCM) within the control solenoid valve assembly continuously monitors the system voltage on the ignition voltage circuit. Lower than normal voltage may be inadequate to operate the transmission control solenoids properly. Improper solenoid operation may cause erratic transmission operation, which may result in internal damage. These DTCs detect high or low TCM voltage for an extended period.

Conditions for Running the DTC

P0562

1. Ignition voltage was greater than 5.0 volts and has not dropped below 2.0 volts.
2. Engine speed is greater than 1, 200 RPM.

P0563

Ignition voltage was greater than 5.0 volts and has not dropped below 2.0 volts.

P2534

1. Engine is running.
2. Normal CAN communication is enabled.

Conditions for Setting the DTC

P0562

TCM detects ignition voltage is 11 volts or less for 4 seconds in a period of 12 seconds.

P0563

TCM detects ignition voltage is 18 volts or greater for 10 seconds.

P2534

The TCM detects ignition voltage between 2.0 volts and 5.0 volts for 7 seconds or greater with the engine running.

Action Taken When the DTC Sets

P0562 and P0563

DTCs P0562 and P0563 are Type C DTCs.

P2534

1. DTC P2534 is a Type A DTC.
2. TCM turns the high side driver OFF.
3. TCM commands maximum line pressure.
4. TCM freezes transmission adaptive functions.
5. TCM commands the torque converter clutch (TCC) OFF.
6. TCM limits the transmission to Reverse and fifth gear operation.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.
9. TCM requests a reduced engine torque.

Conditions for Clearing the DTC

1. DTCs P0562 and P0563 are Type C DTCs.
2. DTC P2534 is a Type A DTC.

Diagnostic Aids

1. Observe the driver information center (DIC) messaging that would indicate the electrical system requires service.
2. Running the engine with a battery charger attached may cause DTC P0563 to set.
3. Inspect for the following conditions: Loose or damaged terminals at the generator Loose or worn generator drive belt

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification

1. Test for 12.6-15 volts between the battery terminals with the engine running, accessories OFF. If not between 12.6-15 volts Refer to «Charging System Test»(/buick/lacrosse/ii-2009-2013/remont/charging-system/#battery-charging-system-and-starting-system-except-hybrid) . IF between 12.6-15 volts
2. Verify the scan tool TCM Ignition Voltage parameter is between 12.6-15.0 volts. If not between 12.6-15 volts Refer to Circuit/System Testing Below If between 12.6-15 volts
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

Circuit/System Testing

Note. You must perform the Circuit/System Verification first.

1. Ignition OFF, and all vehicle systems OFF, disconnect the X1 20-way harness connector at the transmission.
2. Connect the DT-47825-20 adapter harness to the vehicle wire harness X1 20-way transmission connector.
3. Test for less than 5 ohms between the ground circuit terminal 1 and ground at the transmission case. If 5 ohms or greater Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 5 ohms
4. Ignition ON.
5. Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and circuit fuse is open Ignition OFF. Test the B+ circuit for a short to ground. If B+ circuit has a short to ground, repair the short to ground on the circuit. If B+ circuit does not have a short to ground, replace the fuse. If the test lamp illuminates
6. Verify that a test lamp illuminates between the ignition circuit terminal 13 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF. Test for less than 2 ohms in the ignition circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF. Test the ignition circuit for a short to ground. If ignition circuit has a short to ground, repair the short to ground on the circuit. If ignition circuit does not have a short to ground, replace the fuse. If the test lamp illuminates
7. Replace the Q8 control solenoid valve assembly.

Repair Instructions

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Typical Scan Tool Data

Brake Pedal Position Sensor

The brake pedal position (BPP) sensor is part of the engine brake pedal override feature. The engine control module (ECM) continuously monitors the vehicle speed and the position of the brake pedal. These two main inputs, along with other ECM inputs are used to determine if the vehicle is decelerating at the proper speed and rate with the brake pedal applied. When the engine brake pedal override system is active, the ECM reduces engine torque to assist in reducing vehicle speed.

The BPP sensor is a three wire sensor, connected to a 5 V reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 V to the BPP sensor, and also provides a sensor ground path on the low reference circuit. The BPP sensor sends a voltage signal to the ECM on the signal circuit. The voltage on the signal circuit will vary from a voltage greater than 0.25 V when the brake pedal is released to a voltage less than 4.75 V when the brake pedal is fully applied.

Ignition voltage is greater than 10 V.

P057C

BPP sensor voltage is less than 0.25 V for 1 second.

P057D

BPP sensor voltage is greater than 4.75 V for 1 second.

1. DTCs P057C and P057D are type B DTCs
2. Engine torque is reduced to 50 percent of available engine torque.
3. Brake torque management is active at 25 kpa (3.7 PSI) of brake apply pressure.

P057C and P057D are type B DTCs.

Schematic Reference

1. «Automatic Transmission Controls Schematics»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-wiring-schematic-diagrams)
2. «Engine Controls Schematics (LFX)»(/buick/lacrosse/ii-2009-2013/remont/testing-diagnostics/#engine-controlsfuel-36l-wiring-schematic-diagrams)
3. «Exterior Lights Schematics»(/buick/lacrosse/ii-2009-2013/remont/exterior-lights/#lighting-system-wiring-schematic-diagrams)

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, engine OFF, transmission in PARK, service brake pedal released.
2. Verify DTC P0651 is not set. If DTC is set Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If DTC is not set
3. Verify the scan tool Brake Pedal Position Sensor parameter in the ECM Automatic Transmission Data list displays greater than.25 V. If.25 V or less Refer to Circuit/System Testing below. If greater than.25 V
4. Verify the scan tool Brake Pedal Position Sensor parameter changes as the brake pedal is applied and displays less than 4.75 V when the brake pedal is fully applied. If 4.75 V or greater, or the parameter does not change Refer to Circuit/System Testing below. If less than 4.75 V and parameter changes
5. Verify the scan tool Brake Pedal Position Sensor Learned Home Position parameter is within 0.1 V of the Brake Pedal Position Sensor parameter when the brake pedal is fully released. If difference is greater than 0.1 V Command the «Brake Pedal Position Sensor Learn»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__brake-pedal-position-sensor-learn) with a scan tool. If difference is 0.1 V or less
6. Verify the scan tool Brake Pedal Position Sensor parameter transitions smoothly without any spikes or dropouts when slowly applying and releasing the brake. If parameter does not transition smoothly or has spikes or dropouts Refer to Circuit/System Testing below. If parameter transitions smoothly and there are no spikes or dropouts
7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
8. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
9. All OK.

Note. You must perform the Circuit/System Verification first.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector from the B22 Brake Pedal Position Sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the low reference circuit terminal 5 and ground. If 10 ohms or greater Ignition OFF and all systems OFF, disconnect the harness connector at the K20 Engine Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If less than 10 ohms
3. Ignition ON.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 6 and ground. If less than 4.8 V Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the 5 V reference circuit terminal 6 and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2 ohms in the 5 V reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If greater than 5.2 V Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the 5 V reference circuit terminal 6 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K20 Engine Control Module. If between 4.8-5.2V
5. Verify the scan tool Brake Pedal Position Sensor parameter is less than.25 V. If parameter is.25 V or greater Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than.25 V between the signal circuit terminal 4 and ground. If.25 V or greater, repair the short to voltage on the circuit. If less than.25 V, replace the K20 Engine Control Module If less than.25 V
6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 6.
7. Verify the scan tool Brake Pedal Position Sensor parameter is 4.8 V or greater. If less than 4.8 V Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the signal circuit terminal 4 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module.
8. Replace the B22 Brake Pedal Position Sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Brake Pedal Position Sensor Replacement»(/buick/lacrosse/ii-2009-2013/remont/exterior-lights/#lighting-system-repair-instructions__brake-pedal-position-sensor-replacement)
2. Perform the «Brake Pedal Position Sensor Learn»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__brake-pedal-position-sensor-learn) following the replacement of the ECM or BPP sensor, or any repair that effects the BPP sensor alignment.

Control Module References for engine control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptors

Note. DTCs P0601, P0602, P0603, P0604 or P062F could set in other control modules. Verify the DTCs are set in the transmission control module (TCM).

This is an internal fault detection of the control solenoid valve assembly. This fault is handled inside the control solenoid valve assembly and no external circuits are involved.

Ignition voltage is between 8.6 volts and 18.0 volts.

P0601

Read only memory (ROM) test has failed 5 or greater times.

P0602

TCM has not been programmed and is unable to detect the start program.

P0603

TCM has detected a memory checksum error.

P0604

TCM has detected a random access memory (RAM) test error 5 or greater times.

P062F

TCM has detected a non-volatile memory error during power-down.

P0601, P0602, P0603, P0604, or P062F

1. DTCs P0601, P0603, P0604, and P062F are Type A DTCs.
2. TCM limits the transmission to Reverse and 5th gear operation.
3. TCM commands maximum line pressure.
4. TCM forces the torque converter clutch (TCC) OFF.
5. TCM freezes transmission adaptive functions.
6. TCM commands the high side driver OFF.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.

PO602

1. DTC P0602 is a Type C DTC.
2. TCM limits the transmission to Reverse and 5th gear operation.
3. TCM commands maximum line pressure.
4. TCM forces the torque converter clutch (TCC) OFF.
5. TCM freezes transmission adaptive functions.
6. TCM commands the high side driver OFF.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.

PO601, P0603, P0604, or PO62F

DTCs P0601, P0603, P0604, and P062F are Type A DTCs.

PO602

DTC P0602 is a Type C DTC.

Description and Operation

Electronic Component Description for control solenoid valve assembly

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF for 1 minute.
2. Ignition ON.
3. Verify with a scan tool, that DTC P0602 is not set. If DTC P0602 is set Program the K71 transmission control module. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Programming and Setup (6T30/6T40/6T45/6T50)»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-solenoid-valve-and-transmission-control) , «Control Solenoid Valve and Transmission Control Module Assembly Programming and Setup (6T70/6T75)»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-solenoid-valve-and-transmission-control) . If the DTC resets, replace the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) . If DTC P0602 is not set
4. Verify with a scan tool that DTC P0601, P0603, P0604, or P062F is not set. If DTC P0601, P0603, P0604, or P062F is set Replace the Q8 control solenoid valve assembly. If DTC P0601, P0603, P0604 or P062F is not set
5. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

Note. Perform the Reset Transmission Adapts any time a transmission related component is serviced.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The transmission control module (TCM) temperature sensor is located inside of the control solenoid valve assembly which has no serviceable components. The TCM monitors the TCM temperature sensor for over temperature protection.

1. DTC P0634 is not set.
2. Ignition voltage is 8.6-32 V.
3. TCM temperature is between 0-170°C (32-338°F) for 0.25 seconds.

Condition 1

TCM detects an internal temperature condition of 146°C (295°F) or greater for 5 seconds.

Condition 2

Ignition voltage is 18 V or greater and the TCM detects an internal temperature of 50°C (122°F) or greater for 2 seconds.

1. DTC P0634 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd or 5th gear operation.
3. TCM inhibits Tap Up/Down function.
4. TCM inhibits manual shifting of forward gears.
5. TCM commands maximum line pressure.
6. TCM shuts down.

DTC P0634 is a Type A DTC.

During a road test, the TCM temperature should steadily increase to a normal operating temperature, and then stabilize.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON.
2. Verify the scan tool Engine Coolant Temperature parameter was less than 125° C (257° F) when DTC set by reviewing the scan tool Freeze Frame/Failure Records. If 125° C (257° F) or greater Refer to «Engine Overheating»(/buick/lacrosse/ii-2009-2013/remont/cooling-system-mechanical/#engine-cooling-system__engine-overheating) . If less than 125° C (257° F)
3. Verify transmission fluid level and condition is correct. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) . If the transmission fluid level and condition is not correct Repair as necessary. If the transmission fluid level and condition is correct
4. Clear the DTCs from the TCM with a scan tool.
5. Operate the vehicle until normal engine temperature is reached. Verify the scan tool Transmission Fluid Temperature parameter is less than 140° C (284° F). If 140° C (284° F) or greater Ignition OFF. Verify the conditions listed below do not exist: Obstructions to the airflow to the radiator or transmission Radiator damage Transmission cooler damage Transmission cooler pipe kinked or damaged If conditions exist, repair or replace as necessary. If conditions do not exist, refer to «Transmission Fluid Cooler Flushing and Flow Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t40-diagnostic-information-and-procedures__transmission-fluid-cooler-flushing-and-flow) . If less than 140° C (284° F)
6. Verify the DTC does not set. If DTC sets Replace the Q8 Control Solenoid Valve Assembly. If DTC does not set
7. Operate the vehicle within the conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Record data.
8. Verify the DTC does not set. If the DTC sets Replace the Q8 Control Solenoid Valve Assembly. If the DTC does not set
9. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Transmission Fluid Cooler Pipe Connector Replacement - Radiator»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Disconnection and Connection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The transmission control module (TCM) high side driver 1 is located inside of the control solenoid valve assembly, which has no serviceable components. The high side driver 1 provides power to the pressure control solenoids and shift solenoids.

P0658

1. DTC P0658 is not set.
2. High side driver 1 is enabled.

P0659

1. DTC P0659 is not set.
2. Ignition transitions from OFF to ON

P0658

TCM detects an internal open or short to ground in the high side driver 1 circuit for 1 second.

P0659

TCM detects an internal short to voltage on the high side driver 1 for 1 second.

P0658

1. DTC P0658 is a Type A DTC.
2. TCM turns the high side driver OFF.
3. TCM turns OFF all solenoids.
4. TCM commands maximum line pressure.
5. TCM freezes transmission adaptive functions.
6. TCM commands the torque converter clutch (TCC) OFF.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.
9. TCM limits the transmission to Reverse and 5th gear operation.
10. TCM requests a reduced torque value based on input speed.

P0659

DTC P0659 is a Type C DTC.

1. DTC P0658 is a Type A DTC.
2. DTC P0659 is a Type C DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Ignition ON.
2. Verify the scan tool High Side Driver 1 parameter displays ON. If ON is not displayed Refer to Circuit/System testing below. If ON is displayed
3. Engine Running and gear selector lever in the park position.
4. Verify the scan tool parameters listed below do not display Malfunction: High Side Driver 1 Circuit Low Voltage Test Status High Side Driver 1 Circuit Open Test Status High Side Driver 1 Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) If contamination is present Repair as necessary If contamination is not present
3. Verify the resistance is within the specified range for each solenoid listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid Valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT 47825-20 adapter harness between the vehicle wire harness electrical connector and the Q8 Control Solenoid Valve Assembly electrical connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: High Side Driver 1 Circuit Low Voltage Test Status High Side Driver 1 Circuit Open Test Status High Side Driver 1 Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 Control Solenoid Valve Assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) .
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The transmission control module (TCM) temperature sensor is located inside of the control solenoid valve assembly, which has no serviceable components. The TCM temperature sensor provides the temperature of the TCM. This temperature reading is used in various shifting and diagnostic routines in the TCM software. This fault is handled inside the TCM and no external circuits are involved.

P0667

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0658, P0667, P0668, P0669, P06AD, P06AE, P0712, P0713, P0716, P0717, P0722, P0723, P0962, P0963, P0966, P0967, P0970, P0971, P215C, P2720, P2721, P2729, or P2730 is not set.
2. Brake torque is not active.
3. Engine speed is 400-7500 RPM for 5 seconds.
4. Ignition voltage is 8.6-32 V.
5. Engine torque signal is valid.
6. Throttle position signal is valid.

P0668

1. DTC P0668 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0669

1. DTC P0669, P0716, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM.
3. Ignition voltage is 8.6-32 V.

P0667

1. TCM detects a 20-50°C (36-90°F) or greater difference between the transmission fluid temperature and TCM substrate temperature, which depends on the average of the transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
2. TCM detects an 8-10°C (14-18°F) or greater difference between the TCM power up temperature and TCM substrate temperature, which depends on the average of the transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
3. Above conditions have to be met for 5 minutes within a 6 minute period.

P0668

TCM temperature is -249°C (-416°F) or lower for 1 minute.

P0669

TCM temperature is 249°C (480°F) or greater for 1 minute.

1. DTCs P0667, P0668, and P0669 are Type B DTCs.
2. TCM defaults the TCM substrate temperature to a calculated temperature based on the TCM power up temperature.

DTCs P0667, P0668, and P0669 are Type B DTCs.

The TCM temperature sensor is located inside of the control solenoid valve assembly and its output should resemble that of the transmission fluid temperature sensor output. During a road test, the TCM temperature should steadily increase to a normal operating temperature, and then stabilize.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON.
2. Verify the scan tool TCM Temperature parameter is between -249 and +249°C (-416 and +480°F). If not between -249 and +249°C (-416 and +480°F) Replace the Q8 Control Solenoid Valve Assembly. If between -249 and +249°C (-416 and +480°F)
3. Verify the scan tool TCM Temperature parameter increases greater than 2°C (3.5°F) after operating the vehicle at 64 km/h (40 mph) for 10 minutes. If the temperature does not increase greater than 2°C (3.5°F) Replace the Q8 Control Solenoid Valve Assembly If the temperature increases greater than 2°C (3.5°F)
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Replace the Q8 Control Solenoid Valve Assembly If the DTC does not set
6. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The transmission control module (TCM) power up temperature sensor is located inside of the control solenoid valve assembly, which has no serviceable components. The TCM power up temperature sensor provides the temperature of the TCM when the TCM power is ON. This temperature reading is used in various shifting and diagnostic routines and also to protect the control solenoid valve assembly and TCM. This fault is handled inside the TCM and no external circuits are involved.

P06AC

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0658, P0668, P0669, P06AC, P06AD, P06AE, P0712, P0713, P0716, P0717, P0722, P0723, P0962, P0963, P0966, P0967, P0970, P0971, P215C, P2720, P2721, P2729, or P2730 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Brake torque is not active.
5. Engine torque signal is valid.
6. Throttle position signal is valid.

P06AD

1. DTC P06AD, P0716, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P06AE

1. DTC P06AE is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P06AC

1. TCM detects a 20-50° C (36-90°F) or greater difference between the transmission fluid temperature and TCM power up temperature, which depends on the average of transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
2. TCM detects an 8-10° C (14-18°F) or greater difference between the TCM substrate temperature and TCM power up temperature, which depends on the average of the transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
3. Above conditions have to be met for 5 minutes within a 6 minute period.

P06AD

TCM power up temperature is -59°C (-74°F) or less for 1 minute.

P06AE

TCM power up temperature is 164°C (327°F) or greater for 1 minute.

1. DTC P06AC, P06AD, P06AE are Type B DTCs.
2. TCM defaults the TCM power up temperature to a calculated temperature based on the TCM substrate temperature.

DTC P06AC, P06AD, P06AE are Type B DTCs.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation) for control solenoid valve assembly

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, clear the DTCs with a scan tool.
2. Operate the vehicle at 64 km/h (40 mph) for 10 minutes.
3. Verify DTC P06AC, P06AD, or P06AE is not set. If any of the DTCs are set Replace the Q8 Control Solenoid Valve Assembly. If none of the DTCs are set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Replace the Q8 Control Solenoid Valve Assembly. If the DTC does not set
6. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The transmission fluid temperature sensor is located inside of the transmission control module (TCM) assembly which has no serviceable components. The transmission fluid temperature sensor provides transmission fluid temperature to the TCM. This fault is handled inside the TCM and no external circuits are involved.

P0711

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0658, P0668, P0669, P06AD, P06AE, P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0962, P0963, P0966, P0967, P0970, P0971, P215C, P2720, P2721, P2729, or P2730 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Brake torque is not active.
5. Engine torque signal is valid.
6. Throttle position signal is valid.

P0712

1. DTC P0712, P0716, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0713

1. DTC P0713, P0716, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0711

1. TCM detects a 20-50° C (36-90° F) or greater difference between the transmission fluid temperature and the TCM substrate temperature, which depends on the average of the transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
2. TCM detects a 20-50° C (36-90° F) or greater difference between the transmission fluid temperature and the TCM power up temperature, which depends on the average of the transmission fluid temperature, TCM substrate temperature, and TCM power up temperature.
3. Above conditions have to be met for 5 minutes within a 6 minute period.

P0712

Transmission fluid temperature is -74°C (-101°F) or lower for 1 minute.

P0713

Transmission fluid temperature is 174°C (345°F) or greater for 1 minute.

1. DTCs P0711, P0712, and P0713 are Type B DTCs.
2. TCM defaults to a calculated transmission fluid temperature based on the TCM Temperature.

DTCs P0711, P0712, and P0713 are Type B DTCs.

The TCM temperature sensor is located inside of the control solenoid valve assembly and its output should resemble that of the transmission fluid temperature sensor's output. During a road test, the transmission fluid temperature should steadily increase to a normal operating temperature, and then stabilize.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling at the normal operating temperature.
2. Verify the scan tool Transmission Fluid Temperature parameter is between -74 and +174° C (-101 and +345° F). If not between -74 and +174° C (-101 and +345° F) Replace the Q8 Control Solenoid Valve Assembly. If between -74 and +174° C (-101 and +345° F)
3. Verify the scan tool Transmission Fluid Temperature parameter increases greater than 2° C (3.5° F) after operating the vehicle at 64 km/h (40 mph) for 10 minutes. If the Temperature does not increase greater than 2° C (3.6° F) Replace the Q8 Control Solenoid Valve Assembly. If the Temperature increases greater than 2° C (3.6° F)
4. Verify the scan tool Transmission Fluid Temperature and the TCM Temperature parameters are within 20° C (36° F). If the Temperatures are not within 20° C (36° F) Replace the Q8 Control Solenoid Valve Assembly. If the Temperatures are within 20° C (36° F)
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Replace the Q8 Control Solenoid Valve Assembly. If the DTC does not set
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission ISS

ISS/OSS Supply Voltage

The input shaft speed (ISS) sensor is a hall-effect type sensor. The ISS sensor mounts to the inside of the automatic transmission case assembly and connects to the control solenoid valve assembly through a 2-wire harness and connector. The sensor faces the reluctor wheel which is attached to the 4-5-6 clutch and 3-5-R clutch housing. The sensor receives 8.3-9.3 volts on the ISS supply voltage circuit from the transmission control module (TCM). As the 4-5-6 clutch and 3-5-R clutch housing rotates, the sensor produces a signal frequency based on the teeth of the reluctor wheel. This signal is transmitted through the ISS sensor signal circuit to the TCM. The TCM uses the ISS sensor signal to determine line pressure, transmission shift patterns, torque converter clutch (TCC) slip speed, and gear ratio.

P0716

1. DTC P0101, P0102, P0103, P0121, P0122, P0123, P0716, P0717, P0752, P0973, or P0974 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Engine torque signal is valid.
5. Throttle position signal is valid.
6. Vehicle speed is 10 km/h (6 mph) or greater.

P0717

1. DTC P0101, P0102, P0103, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Vehicle speed is 16 km/h (10 mph) or greater.
5. Engine torque is 50 N.m (37 lb ft) or greater.
6. Engine torque signal is valid.

P0716

TCM detects the transmission input shaft speed signal dropped greater than 1350 RPM for 1 second.

P0717 - Condition 1

TCM detects the transmission input shaft speed signal is less than 67 RPM for 5 seconds.

P0717 - Condition 2

The TCM detects that P0722 set and the Transmission input speed is less than 1000 RPM for 5 seconds.

1. DTCs P0716 and P0717 are Type A DTCs.
2. TCM freezes transmission adaptive functions.
3. TCM commands the high side driver OFF.
4. TCM commands TCC OFF.
5. TCM commands maximum line pressure.
6. TCM disables neutral idle.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.
9. Torque management is enabled.
10. TCM limits the transmission to Reverse and 3rd or 5th gear operation.

DTCs P0716 and P0717 are Type A DTCs.

If the scan tool ISS/OSS supply voltage parameter is out of range, the fault could also be caused by the transmission output shaft speed sensor.

Damage or misalignment of the 4-5-6 clutch and 3-5-R clutch housing reluctor machined teeth surface may cause a speed sensor malfunction.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL 38522 Variable Signal Generator.

For equivalent regional tools, refer to Special Tools .

1. Ignition ON.
2. Verify the scan tool ISS/OSS Supply Voltage parameter displays OK. IF OK is not displayed Refer to Circuit/System Testing below. If OK is displayed
3. Engine idling, transmission shift lever in the park position.
4. Verify the scan tool Transmission ISS parameter changes or does not drop out while varying the engine speed. If the Transmission ISS does not vary with engine speed or drops out Refer to Circuit/System Testing below. If the Transmission ISS varies with engine speed and does not drop out
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Ignition OFF, remove the control valve body cover.
2. Connect the vehicle wire harness electrical connector to the Q8 Control Solenoid Valve Assembly electrical connector.
3. Disconnect the B14C Transmission Input Shaft Speed Sensor wiring harness connector from the Q8 Control Solenoid Valve Assembly.
4. Ignition ON.
5. Test for 8.3-9.3 V between the ISS sensor supply voltage circuit terminal A at the Q8 Control Solenoid Valve Assembly, and ground at the transmission case. If not between 8.3-9.3 V Ignition OFF, disconnect the B14A Transmission Output Shaft Speed Sensor wiring harness connector from the Q8 Control Solenoid Valve Assembly. Ignition ON. Test for 8.3-9.3 V between the OSS sensor supply voltage circuit terminal A X3 at the Q8 Control Solenoid Valve Assembly, and ground at the transmission case. If not between 8.3-9.3 V, replace the Q8 Control Solenoid Valve Assembly. If between 8.3-9.3 V, replace the B14A Transmission Output Shaft Speed Sensor. If between 8.3-9.3 V
6. Verify the scan tool Transmission ISS parameter is between 495-505 RPM when performing the input shaft speed test. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If not between 495-505 RPM Replace the Q8 Control Solenoid Valve Assembly. If between 495-505 RPM
7. Verify there is no damage to the reluctor, which is attached to the 4-5-6 clutch and 3-5-R clutch housing assembly, or misalignment between the B14C Transmission Input Shaft Speed Sensor and reluctor. If the reluctor is damaged or misaligned Repair or replace as necessary. If the reluctor is not damaged or misaligned
8. Replace the B14C Transmission Input Shaft Speed Sensor.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Input Speed Sensor Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Output Speed Sensor Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Control Valve Body Cover Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
5. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
6. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission OSS

ISS/OSS Supply Voltage

The automatic transmission output shaft speed (OSS) sensor is a hall-effect type sensor. The sensor faces the front differential transfer drive gear. The sensor receives 8.3-9.3 volts on the OSS sensor supply voltage circuit from the transmission control module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft. This signal is transmitted through the OSS sensor signal circuit to the TCM. The TCM uses the OSS sensor signal to calculate output shaft speed to determine commanded line pressure, transmission shift patterns, torque converter clutch (TCC) slip speed and gear ratio.

P0722

1. DTC P0101, P0102, P0103, P0121, P0122, P0123, P0716, P0717, P0722, or P0723 is not set.
2. Selected range is not PARK or NEUTRAL.
3. Transmission input speed is 1, 000 RPM or greater.
4. Engine speed is 3, 200 RPM or greater.
5. Throttle position is 5 percent or greater.
6. Throttle position signal is valid.
7. Engine torque is 35 N.m (26 lb ft) or greater.
8. Engine torque signal is valid.
9. Transmission fluid temperature is -40°C (-40°F) or greater.
10. Engine speed is 400-7500 RPM for 5 seconds.
11. Ignition voltage is 8.6-32 V.

P0723

1. DTC P0101, P0102, P0103, P0121, P0122, P0123, P0723, P0973, P0974, P0976, or P0977 is not set.
2. Greater than 5 seconds since last transmission upshift or downshift.
3. Engine speed is 400-7500 RPM for 5 seconds.
4. Ignition voltage is 8.6-32 V.

P0722

Transmission output speed is 35 RPM or less for 4.0 seconds.

P0723

1. Transmission output speed is 105 RPM or greater for 0.2 second.
2. TCM detects the transmission output shaft speed dropped greater than 650 RPM for 1.5 seconds.

1. DTCs P0722 and P0723 are Type A DTCs.
2. TCM freezes transmission adaptive functions.
3. TCM turns the high side driver OFF.
4. TCM commands maximum line pressure.
5. TCM inhibits Tap Up/Down function.
6. TCM inhibits manual shifting of forward gears.
7. TCM limits the transmission to Reverse and 3rd or 5th gear operation.

DTCs P0722 and P0723 are Type A DTCs.

1. Damage or misalignment of the front differential transfer drive gear teeth surface or metallic debris on the face of the sensor may cause a speed sensor malfunction.
2. Proper torque of the OSS mounting bolt is critical to proper OSS operation.
3. If the scan tool ISS/OSS Supply Voltage indicates out of range, the fault could also be caused by the transmission input shaft speed sensor.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t40-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t40-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL 38522 Variable Signal Generator

For equivalent regional tools, refer to Special Tools .

1. Ignition ON.
2. Verify the scan tool ISS/OSS Supply Voltage parameter displays OK. If OK is not displayed Refer to Circuit/System Testing below. If OK is displayed
3. Verify the scan tool Transmission OSS parameter changes with vehicle speed or does not drop out while operating the vehicle at 16-32 km/h (10-20 mph). If the Transmission OSS does not vary with vehicle speed or has dropouts Refer to Circuit/System Testing below. If the Transmission OSS varies with vehicle speed and does not drop out
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
6. All OK.

1. Ignition OFF, remove the control valve body cover.
2. Connect the vehicle wire harness electrical connector to the Q8 Control Solenoid Valve Assembly electrical connector.
3. Disconnect the B14A Transmission Output Shaft Speed Sensor wiring harness connector from the Q8 Control Solenoid Valve Assembly.
4. Ignition ON.
5. Test for 8.3-9.3 V between the OSS sensor supply voltage circuit terminal A at the Q8 Control Solenoid Valve Assembly, and ground at the transmission case. If not between 8.3-9.3 V Ignition OFF, disconnect the B14C Transmission Input Shaft Speed Sensor wiring harness connector from the Q8 Control Solenoid Valve Assembly. Ignition ON. Test for 8.3-9.3 V between the OSS sensor supply voltage circuit terminal A X4 electrical connector at the Q8 Control Solenoid Valve Assembly, and ground at the transmission case. If not between 8.3-9.3 V, replace the Q8 Control Solenoid Valve Assembly. If between 8.3-9.3 V, replace the B14C Transmission Input Shaft Speed Sensor. If between 8.3-9.3 V
6. Verify the scan tool Transmission OSS parameter is between 256-266 RPM when performing the output shaft speed test. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If not between 256-266 RPM Replace the Q8 Control Solenoid Valve Assembly. If between 256-266 RPM
7. Verify there is no damage to the front differential transfer drive gear teeth surface or misalignment with the B14A Transmission Output Speed Sensor. If the front differential transfer drive gear is damaged or is misaligned Repair or replace as necessary. If the front differential transfer drive gear is not damaged or misaligned.
8. Replace the B14A Transmission Output Speed Sensor.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. Refer to «Control Valve Body Cover Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. «Output Speed Sensor Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Input Speed Sensor Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
5. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The torque converter clutch (TCC) pressure control solenoid is part of the control solenoid valve assembly which has no serviceable components. The TCC pressure control solenoid is a normally low pressure control solenoid. The TCC pressure control solenoid regulates transmission fluid to the TCC regulator valve in the lower valve body and the TCC control valve in the pump cover. When vehicle operating conditions are appropriate to apply the converter clutch, the transmission control module (TCM) will increase current flow to the TCC pressure control solenoid, thereby increasing pressure directed to the TCC control valve. The increase in fluid pressure moves the TCC control valve to the apply position, and moves the TCC regulator apply valve to the regulating position. The TCC regulator valve regulates TCC apply fluid pressure proportional to TCC solenoid pressure. When the TCC is fully applied, the engine is coupled directly to the transmission. TCC release is accomplished by the TCM decreasing current flow to the TCC PC solenoid. This results in decreasing the apply pressure which allows the TCC control valve to move to the release position. The TCM calculates torque converter slip speed based on the speed signal from the input shaft speed sensor and the engine speed RPM provided by the engine control module.

P0741

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, P0741, P0742, P2763, or P2764 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Transmission fluid temperature is between -6.7 to +130°C (20-266°F).
5. Throttle position is 8 percent or greater.
6. Engine torque is 50 N.m (36 lb ft) or greater.
7. Engine torque signal is valid.
8. Throttle position signal is valid.
9. TCM detects the transmission gear ratios listed below for the commanded gear when TCC is commanded ON: 2nd gear ratio is between 2.67-3.07. 3rd gear ratio is between 1.71-1.97. 4th gear ratio is between 1.32-1.51. 5th gear is between 0.93-1.07. 6th gear is between 0.69-0.79.

P0742

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, P0741, P0742, P2763, or P2764 is not set.
2. Commanded range is 2nd gear or higher.
3. Ignition voltage is 8.6 V or greater.
4. Transmission fluid temperature is between 18-130°C (64-266°F).
5. Throttle position is 5 percent or greater.
6. Engine torque is 80 N.m (59 lb ft) or greater.
7. Engine speed is 400-7500 RPM for 5 seconds.
8. Vehicle speed is 1 km/h (.6 mph) or greater.
9. Engine speed is 500 RPM or greater
10. Engine torque signal is valid.
11. Throttle position signal is valid.
12. TCC is commanded OFF.

P0741

1. TCC Pressure command is 800 kPa (116 psi) or greater for 2 seconds.
2. TCM detects TCC slip of 50 RPM or greater for 5 seconds.
3. The above conditions must occur 3 times.

P0742

TCM detects the TCC slip between -50 and +13 RPM for 2.5 seconds when the TCC is commanded OFF. This condition must occur 6 times.

P0741

1. DTC P0741 is a Type B DTC.
2. TCM inhibits 6th gear.
3. TCM commands TCC OFF.
4. TCM forces hot mode shift pattern.

P0742

1. DTC P0742 is a Type A DTC.
2. TCM freezes transmission adaptive functions.
3. TCM forces hot mode shift pattern.
4. TCM commands the TCC ON.

P0741

DTC P0741 is a Type B DTC.

P0742

DTC P0742 is a Type A DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. DT-47825-100 Solenoid Test Plate
2. DT-47825-20 Adapter Harness
3. J-21867 Pressure Gauge

For equivalent regional tools, refer to Special Tools .

Note. If other DTCs are set, diagnose those DTCs first.

1. Engine idling with transmission shift lever in the park position, with parking brake applied and drive wheels chocked.
2. Verify the transmission fluid level and condition is correct. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) . If the transmission fluid level and condition is not correct Repair as necessary If the transmission fluid level and condition is correct
3. Ignition ON, clear the TCM DTCs with a scan tool.
4. Verify DTC P0741 or P0742 does not set while performing a road test. Refer to «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . If DTC P0741 or P0742 sets Refer to Circuit/System Testing below. If DTC P0741 or P0742 did not set
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Engine idling at the normal operating temperature.
2. Verify the transmission line pressures are within the specified range. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If the pressures are not within range Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) . If the pressures are within range
3. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
4. Verify a pressure change occurs for all solenoids when performing the solenoid test. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If a pressure change does not occur Replace the Q8 Control Solenoid Valve Assembly. If a pressure change occurs
5. Verify the mechanical conditions listed below do not exist. Repair or replace as necessary.

P0741 - Upper Valve Body

Release exhaust port/orifice plugged or blocked.

P0741 or P0742 - Upper Valve Body

Torque converter clutch regulator valve stuck/sticking - debris, binding, damaged valve, or scored bore.

P0741 - Channel Plate and Spacer Plate

Oil channels or orifices blocked by debris.

P0741 - Torque Converter

1. Torque converter clutch delamination or material worn off.
2. Converter bolts too long damaging the clutch apply surface.
3. Damaged seal.

P0741 - Support

Damaged seal.

P0741 or P0742 - Transmission Case Cover

1. Pressure release blow-off not seating/sealing.
2. Damaged spring.

P0741 - Turbine Shaft

O-ring seal cut or damaged

P0741 or P0742 Q8 Control Solenoid Valve Assembly

1. Torque converter clutch pressure control solenoid stuck OFF or leaking.
2. Torque converter clutch pressure control solenoid stuck ON.
3. Control signal fluid supply leak due to valve body filter plate assembly cracked, or damaged gasket seal.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Valve Lower Body and Upper Body Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Torque Converter Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
5. «Torque Converter Installation»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
6. «Torque Converter and Differential Housing, Front Differential Transfer Drive Gear, and Front Differential Carrier Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle) , and «Torque Converter and Differential Housing Installation»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
7. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for Control Solenoid Valve Assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Shift solenoid valve 1 is part of the control solenoid valve assembly, which has no serviceable components. The solenoid operates by the transmission control module (TCM) turning the low side driver ON or OFF. When the shift solenoid valve 1 is commanded OFF, the plunger forces the metering ball against the actuator feed limit seat, blocking the flow and any existing pressure is exhausted through the exhaust port. When the shift solenoid valve 1 is commanded ON, the internal plunger moves, allowing the metering valve to move away from the actuator feed limit seat and against the exhaust seat, creating signal fluid pressure. The signal fluid pressure acts against the clutch select valve 2 to overcome the valve spring force, moving the valve to the apply position. Fluid pressure from the R1/4-5-6 regulator valve flows through clutch select valve 2 and is directed to either the low and reverse clutch or the 4-5-6 clutch, depending on the position of clutch select valve 2.

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6-32 V.
3. Engine speed is 400-7500 RPM for 5 seconds.
4. Throttle position signal is valid.
5. Engine torque signal is valid.
6. High side driver is enabled.
7. Output shaft speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
8. Transmission fluid temperature is -6.6°C (20°F) or greater.

P0751

1. Commanded gear is 1st.
2. TCM detects gear ratio 1.34-1.48.
3. Gear slip is 400 RPM or greater for 2 seconds.
4. Above conditions have to occur 8 times.

P0752

1. Commanded gear is 3rd
2. Transmission has achieved 1st or 2nd.
3. Gear slip is 400 RPM or greater for 3 seconds.
4. TCM commands 4th gear if above conditions exist and detects a gear ratio of 4.26-4.71 for 3 seconds.
5. The conditions listed above have to occur 5 times.

P0751

1. DTC P0751 is a Type B DTC.
2. TCM inhibits 1st gear.
3. TCM inhibits neutral idle.

P0752

1. DTC P0752 is a Type A DTC.
2. TCM freezes transmission adaptive functions.
3. TCM commands maximum line pressure.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM commands second gear if output speed is less than 1350 RPM, or neutral if output speed is 1350 RPM or greater.
7. TCM inhibits neutral idle.

1. DTC P0751 is a Type B DTC.
2. DTC P0752 is a Type A DTC.

Before performing a road test, configure and setup the scan tool for snapshot mode. This allows you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)
4. «Drive Range, First Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__drive-range-first-gear)
5. «Drive Range, Third Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__drive-range-third-gear)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling at the normal operating temperature, gear selector in the Park position, with parking brake applied and drive wheels chocked.
2. Verify the transmission fluid level and condition is correct. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) . If the transmission fluid level and condition is not correct Repair as necessary If the transmission fluid level and condition is correct
3. From a stop, accelerate to 72 km/h (45 mph) with the calculated throttle position greater than 15 percent. Perform this test 8 times.
4. Verify DTC P0751 or P0752 did not set. If DTC P0751 or P0752 set Refer to Circuit/System Testing below. If DTC P0751 or P0752 did not set
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Engine idling at the normal operating temperature.
2. Verify the transmission line pressures are within the specified ranges. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If the pressures are not within range Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) If the pressures are within range
3. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
4. Verify a pressure change occurs for all solenoids when performing the solenoid test. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If a pressure change does not occur Replace the Q8 Control Solenoid Valve Assembly. If a pressure change occurs
5. Verify the mechanical conditions listed below do not exist. Repair or replace as necessary.

P0751 - Upper Control Valve Body

1. Clutch select valve 2 bore plug undersized causing a leak - plug should be a valve fit in the bore.
2. Check ball #2 - missing, damaged or malformed, or damage to the seat causing leakage.

P0751 or P0752 - Upper Control Valve Body

Clutch select valve 2 stuck from debris, sediment, binding, or a scored bore.

P0751 or P0752 - Channel Plate and Spacer Plate

Oil channels or orifices blocked by debris.

P0751 - Lower Control Valve Body

1. Shift solenoid 1 - not pressurizing, stuck OFF or leaking.
2. Shift solenoid 1 - not exhausting, stuck ON.

P0751 or P0752 - Q8 Control Solenoid Valve Assembly

1. Shift solenoid valve 1 stuck OFF or leaking.
2. Shift solenoid valve 1 stuck ON.
3. Valve body filter plate assembly cracked, blocked, or damaged gasket seal.
4. Pressure control solenoid valve 3 stuck ON, stuck OFF, or leaking. Low and Reverse, and 4-5-6 regulator valve stuck or sticking from debris, sediment, binding or scored bore.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Shift solenoid valve 2 is part of the control solenoid valve assembly, which has no serviceable components. Shift solenoid valve 2 is a normally closed solenoid valve and controls fluid to the clutch select valve 3. The solenoid operates by the transmission control module (TCM) by turning the low side driver ON or OFF. When the shift solenoid valve 2 is commanded OFF, the plunger forces the metering ball against the actuator feed limit seat, blocking the flow and any existing pressure is exhausted through the exhaust port. When shift solenoid valve 2 is commanded ON, the internal plunger moves and allows the metering ball to move away from the feed seat and against the exhaust seat, creating signal fluid pressure. The signal fluid acts against the clutch select valve 3 to overcome the valve spring force, moving it to the apply position. Shift solenoid valve 2 is commanded OFF in Reverse, and commanded ON in Park, Neutral, Drive 1 Engine Braking, and Drive 1-6 gear ranges.

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. High side driver is enabled.
4. Ignition voltage is 8.6-32 V.
5. Throttle position signal is valid.
6. Transmission fluid temperature is -6.6°C (20°F) or greater.
7. Output shaft speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater

1. Commanded Gear is 1st locked.
2. Gearbox Slip is 400 RPM or greater for 3 seconds.
3. If above conditions exist, the TCM commands second gear. If the gear ratio is between 2.72-3.01 for 1 second, the counter will increment. DTC will set after 3 occurrences.

1. DTC P0756 is a Type A DTC.
2. TCM inhibits Tap Up/Down function.
3. TCM inhibits manual shifting of forward gears.
4. TCM commands maximum line pressure.
5. TCM freezes transmission adaptive functions.
6. TCM commands second gear if output speed is less than 1350 RPM, or neutral if output speed is 1350 RPM or greater.

DTC P0756 is a Type A DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)
4. «Drive Range, First Gear Engine Braking»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__drive-range-first-gear-engine-braking)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. DT-47825-100 Solenoid Test Plate
2. DT-47825-20 Adapter Harness
3. J-21867 Pressure Gauge

For equivalent regional tools, refer to Special Tools .

1. Engine idling in Park position, with parking brake applied and drive wheels chocked.
2. Verify the transmission fluid level and condition is correct. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) . If the transmission fluid level and condition is not correct Repair as necessary. If the transmission fluid level and condition is correct
3. Ignition ON, clear the TCM DTCs with a scan tool.
4. Engine running, brakes applied, transmission gear shift selector in Reverse. Shift to Drive and accelerate to 56 km/h (35 mph) with calculated throttle position greater than 15 percent. Perform this test 5 consecutive times. Verify DTC P0756 did not set. If DTC P0756 set Refer to Circuit/System Testing below. If DTC P0756 did not set
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Engine idling at the normal operating temperature.
2. Verify the transmission line pressures are within the specified range. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If the pressures are not within range Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) . If the pressures are within range
3. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
4. Verify a pressure change occurs for all solenoids when performing the solenoid test. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If a pressure change does not occur Replace the Q8 Control Solenoid Valve Assembly. If a pressure change occurs
5. Verify the mechanical conditions listed below do not exist. Repair or replace as necessary.

Upper Control Valve Body

1. Clutch select valve 3 stuck from debris, sediment, binding or scored bore
2. Clutch select valve 3 bore plug undersized causing a leak - plug should be a valve fit in the bore.
3. Check ball #3 - missing, damaged or malformed, or damage to the seat causing leakage.

Channel Plate and Spacer Plate

Oil channels or orifices blocked by debris.

Mechanical Diode

Broken or not capable of holding torque.

Pump Assembly

Fluid pump vanes or fluid pump rotor broken

Pump Seal

Seal is torn or cut, causing a small leak that is overcome with enough speed and pump capacity.

Q8 Control Solenoid Valve Assembly

1. Shift solenoid 2 not pressurizing - stuck OFF or leaking.
2. Valve body filter plate assembly cracked, blocked, or damaged gasket seal.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Valve Upper Body Assembly Cleaning and Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
4. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The clutch pressure control (PC) solenoid 2 is part of the control solenoid valve assembly, which has no serviceable components. The PC solenoid 2 regulates transmission fluid pressure to the 3-5-Reverse clutch regulator valve which controls pressure to the 3-5-Reverse clutch. The transmission control module (TCM) calculates gear ratio based on the RPM signals from the input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.

P0776

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. Transmission fluid temperature (TFT) is -7°C (19°F) or greater.
5. Transmission output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
6. Throttle position signal is valid.
7. High side driver is enabled.

P0777

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. TFT is -7°C (19°F) or greater.
5. Engine torque is 20 N.m (15 lb ft) or greater.
6. Transmission output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
7. Throttle position signal is valid.
8. High side driver is enabled.

P0776

TCM has detected an incorrect gear ratio or neutral condition when the 3-5-Reverse clutch is commanded ON. This condition must occur 3 times.

P0777

TCM has detected an incorrect gear ratio change when the 3-5-Reverse clutch is commanded OFF during a shift or when 3rd ratio is detected in 1st gear. This condition must occur 3 times.

P0776

1. DTC P0776 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM inhibits Tap Up/Down function.
4. TCM freezes transmission adaptive functions.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse, 2nd, and 4th gear operation.
7. TCM inhibits auto grade braking.

P0777

1. DTC P0777 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM inhibits Tap Up/Down function.
4. TCM inhibits manual shifting of forward gears.
5. TCM freezes transmission adaptive functions.
6. TCM limits the transmission to 3rd gear and Reverse operation.
7. TCM inhibits auto grade braking.

Conditions for Clearing the DIC/DTC

DTCs P0776 and P0777 are Type A DTCs.

Before performing a road test, configure and setup the scan tool for snapshot mode. This will allow you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Verify correct transmission fluid level and condition. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
3. Verify with a scan tool the Transmission Fluid Pressure Switch 1 parameter values are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 1 Refer to Circuit/System Testing below. If TFP switch 1 values are correct
4. Gear select lever in Drive range. Verify the Transmission Fluid Pressure Switch 1 parameter states are correct for all forward ranges when commanded with a scan tool. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 1 Refer to Circuit/System Testing below. If TFP switch 1 values are correct
5. Ignition ON, clear the TCM DTCs.
6. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . Verify the transmission operation performs as indicated in the road test instructions and DTC P0776 or P0777 did not set. If DTC P0776 or P0777 sets Refer to Circuit/System Testing below. If DTC P0776 or P0777 did not set
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Verify the transmission line pressures are within the ranges specified in the Line PC Solenoid Valve Pressure table. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If line pressures are not within the specified ranges Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . A pressure change should occur for each solenoid valve. If a pressure change does not occur for each solenoid Replace the Q8 control solenoid valve assembly If a pressure change occurs for each solenoid
4. Listed in the table below, are conditions for each component that could set DTC P0776 or P0777. Carefully inspect each component for that condition. Repair or replace as necessary.

DTC P0776 or P0777

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Valve Lower Body and Upper Body Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
2. «Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The clutch pressure control (PC) solenoid 3 is part of the control solenoid valve assembly, which has no serviceable components. The PC solenoid 3 regulates transmission fluid pressure (TFP) to the R1/4-5-6 clutch regulator valve which controls pressure to the low and reverse clutch and the 4-5-6 clutch. The transmission control module (TCM) calculates gear ratio based on the RPM signals from the input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.

P0796

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. Output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
5. Throttle position signal is valid.
6. High side driver is enabled.
7. Transmission fluid temperature (TFT) is -7°C (19°F) or greater.

P0797

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. Output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
5. Throttle position signal is valid.
6. High side driver is enabled.
7. TFT is -7°C (19°F) or greater.
8. Engine torque is 20 N.m (15 lb ft) or greater when 1st gear is commanded.

P0796

The TCM has detected an incorrect gear ratio or neutral condition when the low and reverse clutch or the 4-5-6 clutch is commanded ON. This condition must occur 3 times.

P0797

The TCM has detected an incorrect gear ratio change when the low and reverse clutch or the 4-5-6 clutch is commanded OFF during a shift or when 4th ratio is detected in 1st gear. This condition must occur 3 times.

P0796

1. DTC P0796 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM freezes transmission adaptive functions.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse, 1st, and 3rd gear operation.
7. TCM inhibits auto grade braking.

P0797

1. DTC P0797 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM freezes transmission adaptive functions.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse and 4th gear operation.
7. TCM inhibits neutral idle.
8. TCM requests a reduced engine torque based on input speed.

DTCs P0796 and P0797 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Verify correct transmission fluid level and condition. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
3. Verify with a scan tool the Transmission Fluid Pressure Switch 5 parameter values are correct for the Park, Reverse, and Neutral range gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 5 Refer to Circuit/System Testing below. If TFP switch 5 values are correct
4. Gear select lever in Drive range. Verify the Transmission Fluid Pressure Switch 5 parameter states are correct for all forward ranges when commanded with a scan tool. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 5 Refer to Circuit/System Testing below. If TFP switch 5 values are correct
5. Ignition ON, clear the TCM DTCs.
6. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . Verify the transmission operation performs as indicated in the road test instructions and DTC P0796 or P0797 did not set. If DTC P0796 or P0797 sets Refer to Circuit/System Testing below. If DTC P0796 or P0797 did not set
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Verify the transmission line pressures are within the ranges specified in the Line PC Solenoid Valve Pressure table. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) If line pressures are not within the specified ranges Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid valve. If a pressure change does not occur for each solenoid Replace the Q8 control solenoid valve assembly. If a pressure change occurs for each solenoid
4. Listed in the table below, are conditions for each component that could set DTC P0796 or P0797. Carefully inspect each component for that condition. Repair or replace as necessary.

DTC P0796 or P0797

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Valve Lower Body and Upper Body Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
2. «Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle) , and «3-5-Reverse and 4-5-6 Clutch Housing Disassemble»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Driver Shift Request

When the shift lever is moved left of the D position, the transmission will enter sport mode. With the shift lever in this position, the transmission will enter manual mode if the gear shift lever is pressed forward or rearward. This allows the operator to select an upshift by pressing the gear shift lever forward, and downshift by pressing the gear shift lever rearward. The body control module (BCM) supplies an ignition circuit and a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is left of the D position, a voltage drop occurs across the resistor network. When the gear shift lever is pressed forward or rearward, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module to perform the upshift or downshift.

P0815 or P0816

1. DTC P0815, P0816, P0826, P1761, P182E, P1876, P1877, or P1915 is not set.
2. Time since the range change is 1 second or greater.
3. Engine speed is 400 RPM or greater for 5 seconds.
4. Ignition voltage is 8.6 volts or greater.

P0826

1. Engine speed is 400 RPM or greater for 5 seconds.
2. Ignition voltage is 8.6 volts or greater.
3. DTC P0826 or P1761 is not set.

P0815 - Condition 1

TCM detects an upshift request for 1 second in Park or Neutral.

P0815 - Condition 2

TCM detects an upshift request for 10 minutes in any forward range.

P0816 - Condition 1

TCM detects a downshift request for 1 second in Park or Neutral.

P0816 - Condition 2

TCM detects a downshift request for 10 minutes in any forward range.

P0826

TCM detects an invalid voltage on the Tap up/Tap down signal circuit for 1 minute.

1. DTCs P0815, P0816, and P0826 are Type C DTCs.
2. TCM inhibits Tap Up/Down function.
3. TCM inhibits manual shifting of forward gears.

DTCs P0815, P0816, and P0826 are Type C DTCs.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, engine OFF.
2. Verify with a scan tool no internal mode switch (IMS) DTCs set. If IMS DTCs were set Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If IMS DTCs are not set
3. Verify with a scan tool the Driver Shift Control Mode parameter displays Inactive with the shift lever in the Park, Reverse, Neutral, and Drive positions, and Active with the gear shift lever left of the D position. If the parameter does not display the correct values Refer to Circuit/System Testing below. If the parameter displays the correct value
4. Shift lever left of the D position, verify the scan tool Driver Shift Request parameter changes from None to Upshift when the shift lever is pressed forward, and from None to Downshift when the shift lever is pressed rearward. If the parameter does not display the correct values Refer to Circuit/System Testing below. If the parameter displays the correct value
5. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, disconnect the harness connector from the S3 transmission shift lever.
2. Test for less than 10 ohms between the shift lever harness connector terminal 2 and ground. If 10 ohms or greater Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the S3 transmission shift lever harness connector ignition circuit terminal 1 and ground circuit terminal 2. If the test lamp does not illuminate Ignition OFF, disconnect the harness connector at the K9 body control module. Test for less than 2 ohms in the ignition circuit end to end. If 2 ohms or greater, repair the ignition circuit. If less than 2 ohms, replace the K9 body control module. If the test lamp illuminates
5. Ignition OFF, disconnect the harness connector at the K9 body control module.
6. Test for infinite resistance between the S3 transmission shift lever harness connector signal circuit terminal 3 and ground. If less than infinite resistance Repair the short to ground in the circuit. If infinite resistance
7. Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater Repair the open/high resistance in the circuit. If less than 2 ohms
8. Connect the K9 body control module harness connector, ignition ON.
9. Verify the scan tool Driver Shift Control parameter displays inactive. If Driver Shift Control Mode Parameter does not display Inactive Replace the K9 body control module. If Driver Shift Control Parameter displays Inactive
10. Test for 11-13 volts at the S3 transmission shift lever harness connector between signal circuit terminal 3 and ground. If not between 11-13 volts Replace the K9 body control module. If between 11-13 volts
11. Ignition OFF, connect the S3 transmission shift lever harness connector, Ignition ON.
12. Test for 11-13 volts by back probing the transmission shift lever connector between terminal 3 and ground with the shift lever in Park, Reverse, Neutral, and Drive. If not between 11-13 volts Replace the S3 transmission shift lever assembly. If between 11-13 volts
13. Shift Lever left of D position
14. Test for 8.0-10.6 volts between S3 transmission shift lever connector terminal 3 and ground. If not between 8.0-10.6 volts Replace the S3 transmission shift lever. If between 8.0-10.6 volts
15. Test for 5.1-7.3 volts between S3 transmission shift lever connector terminal 3 and ground with the shift lever pressed rearward. If not between 5.1-7.3 volts Replace the S3 transmission shift lever. If between 5.1-7.3 volts
16. Test for 2.0-4.6 volts between S3 transmission shift lever connector terminal 3 and ground with the shift lever pressed forward. If not between 2.0-4.6 volts Replace the S3 transmission shift lever. If between 2.0-4.6 volts
17. Replace the K9 body control module.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for BCM or control solenoid valve assembly replacement, setup and programming
2. «Transmission Control Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission Fluid Pressure Switch 1

Transmission Fluid Pressure Switch 3

Transmission Fluid Pressure Switch 4

Transmission Fluid Pressure Switch 5

The transmission fluid pressure (TFP) switch 1 is part of the control solenoid valve assembly, which has no serviceable components. The transmission control module (TCM) supplies a signal circuit to the TFP Switch 1. The TFP Switch 1 has an internal case ground. TFP Switch 1 is normally closed or LOW. When oil pressure is present at the TFP Switch 1, the switch is open or HIGH. The normally high clutch pressure control (PC) solenoid 2 controls pressure to the 3-5 reverse clutch regulator valve. The TCM monitors the TFP switch 1 to determine the position of the 3-5 reverse clutch regulator valve. When the 3-5 reverse clutch is commanded OFF, pressure is present on the TFP switch 1. When the 3-5 reverse clutch is commanded ON, the 3-5 reverse clutch regulator valve moves and pressure to the TFP switch 1 is exhausted through the 3-5 reverse clutch regulator valve.

P0842 or P0843

1. DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.
2. High side driver is enabled.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. Engine speed is 550 RPM or greater.
5. Ignition voltage is 8.6 volts or greater.
6. Transmission fluid temperature (TFT) is between -7 to +120°C (19-248°F).

P0842

The TCM detects that the TFP switch 1 signal voltage remains LOW after the 3-5-Reverse clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 25 counts are accumulated.

P0843

The TCM detects that the TFP switch 1 signal voltage remains HIGH after the 3-5-Reverse clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 35 counts are accumulated.

1. DTCs P0842 and P0843 are Type C DTCs.
2. TCM freezes transmission adaptive functions for the 3-5-Reverse clutch.

DTCs P0842 and P0843 are Type C DTCs.

A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation) for control solenoid valve assembly

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Engine idling in Park with parking brake applied, and drive wheels chocked.
2. Verify with a scan tool the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
3. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for each forward range with the gear select lever in Drive, using the scan tool to command all forward ranges. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF. Remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
3. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
4. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil. If any TFP Switch parameter does not change states Replace the Q8 control solenoid valve assembly. If all TFP Switch parameters change states
5. Inspect the channel plate, spacer plate, and filter plate for debris and blocked orifices.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, or programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

PNP Switch

The transmission manual shift shaft switch assembly, also known as the internal mode switch (IMS), is a sliding contact switch attached to the manual shift shaft inside the transmission case. The park/neutral position (PNP) switch is integrated into the IMS and connects to the transmission control module (TCM) lead-frame through a short wire harness. The circuit uses the TCM as a pass-through connector only. The park/neutral signal is sent from the park/neutral switch directly to the engine control module (ECM) and is used for engine start enable.

1. Ignition voltage is between 8-18 volts.
2. Engine speed is greater than 1, 000 RPM.

P0850 and P0851

1. ECM detects the park/neutral switch signal equals 0 volts when the IMS reports a Drive range for 0.2 second.
2. Throttle position is 10 percent or greater.
3. Engine torque is 75 N.m (55 lb ft) or greater.
4. Vehicle speed is 10 km/h (6 mph) or greater.

P0852

ECM detects the park/neutral switch signal equals 12 volts (in-gear) when the IMS reports a park/neutral range for 0.2 second.

1. DTCs P0850, P0851, and P0852 are Type C DTCs.
2. ECM uses IMS range for engine start-up.

DTCs P0850, P0851, and P0852 are Type C DTCs.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Electronic Component Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. If there are any other transmission DTCs set, diagnose those DTCs first. Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Ignition ON.
3. Verify the gear shift lever position matches the scan tool TCM Internal Mode Switch parameter while slowly moving the gear shift lever from Park through all ranges. If the parameter is not correct for each lever position Refer to «Range Selector Lever Cable Adjustment»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t40-repair-instructions-on-vehicle__range-selector-lever-cable-adjustment) . If the parameter is correct for each lever position
4. Verify the scan tool ECM Park/Neutral Position Switch parameter displays Park/Neutral when in Park or Neutral and In-Gear when in Reverse or Drive. If the parameter is not correct for each lever position Refer to Circuit/System Testing below. If the parameter is correct for each lever position
5. Verify the scan tool TCM IMS A/B/C/P parameter displays the correct values while moving the gear shift lever from Park through all ranges. Refer to «Transmission Internal Mode Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-internal-mode-switch-logic) . If the parameter is not correct for each lever position Refer to Circuit/System Testing below. If the parameter is correct for each lever position
6. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, disconnect the X1 20-way harness connector at the transmission.
2. Install the DT-47825-20 harness to the vehicle wire harness X1 20-way transmission connector.
3. Ignition ON.
4. Test for less 11-13 ohms between the terminal 20 at the DT-47825-20 harness and ground. If not between 11-13 volts Ignition OFF. Test the Park/Neutral signal circuit for a short to ground. If circuit has a short to ground, repair the wire. If circuit does not have a short to ground. Test for less than 2 ohms in the Park/Neutral signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 engine control module. If between 11-13 volts
5. Disconnect the DT-47825-20 harness from the vehicle wire harness X1 20-way transmission connector.
6. Remove the control valve body cover. Refer to «Control Valve Body Cover Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
7. Connect the vehicle wire harness X1 20-way transmission electrical connector to the Q8 control solenoid valve assembly.
8. Disconnect the B15 IMS connector X2 at the Q8 control solenoid valve assembly.
9. Ignition ON.
10. Verify the scan tool ECM Park/Neutral Position Switch parameter displays In Gear. If In Gear is not displayed Ignition OFF. Test the Park/Neutral signal circuit for a short to ground. If circuit has a short to ground, repair the wire. If circuit does not have a short to ground, replace the K20 engine control module. If parameter displays In Gear
11. Verify the scan tool TCM IMS A/B/C/P parameter displays High for all 4 signal circuits. If High is not displayed Replace the Q8 control solenoid valve assembly. If High is displayed
12. Test for 11 volts or greater between terminal A on the X2 connector at the Q8 control solenoid valve assembly and ground at the transmission case. If less than 11 volts Replace the Q8 control solenoid valve assembly. If 11 volts or greater
13. Connect a 3-amp fused jumper wire between park/neutral signal circuit terminal F X2 and ground circuit terminal A X2 on the Q8 control solenoid valve assembly. Verify the Park/Neutral Position Switch parameter changes from In Gear to Park/Neutral when the signal circuit is connected to ground. If parameter does not change from In Gear to Park/Neutral Ignition OFF. Test for less than 2 ohms in the Park/Neutral signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit If less than 2 ohms, replace the K20 engine control module If parameter changes from IN Gear to Park/Neutral
14. Connect a 3-amp fused jumper wire between each transmission range signal circuit terminal listed below and the IMS ground circuit, terminal A on the TCM assembly. Verify the scan tool TCM IMS A/B/C/P parameter displays Low when the terminal is connected to the IMS ground. Switch Signal A terminal E to ground circuit terminal A Switch Signal B terminal D to ground circuit terminal A Switch Signal C terminal C to ground circuit terminal A Switch Signal P terminal B to ground circuit terminal A If any parameter does not display the correct value Replace the Q8 control solenoid valve assembly. If parameter displays the correct value
15. Replace the B15 transmission internal mode switch.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ECM or control solenoid valve assembly replacement, setup, and programming
2. «Range Selector Lever Cable Adjustment»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle__range-selector-lever-cable-adjustment)
3. «Control Valve Body Cover Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Manual Shift Detent Lever with Shaft Position Switch Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission Fluid Pressure Switch 1

Transmission Fluid Pressure Switch 3

Transmission Fluid Pressure Switch 4

Transmission Fluid Pressure Switch 5

The transmission fluid pressure (TFP) switch 3 is part of the control solenoid valve assembly, which has no serviceable components. The transmission control module (TCM) supplies a signal circuit to the TFP switch 3. The TFP switch 3 has an internal case ground. The TFP switch 3 is normally closed or LOW. When oil pressure is present at the TFP switch 3, the switch is open or HIGH. The normally low clutch pressure control (PC) solenoid 4 controls pressure to the 2-6 clutch regulator valve. The TCM monitors the TFP switch 3 to determine the position of the 2-6 clutch regulator valve. When the 2-6 clutch is commanded OFF, pressure is present on the TFP switch 3. When the 2-6 clutch is commanded ON, the 2-6 clutch regulator valve moves and pressure to the TFP switch 3 is exhausted through the 2-6 clutch regulator valve.

P0872 or P0873

1. DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.
2. High side driver is enabled.
3. Engine speed is 400 RPM or greater for 5 seconds.
4. Engine speed is 550 RPM or greater.
5. Ignition voltage is 8.6 volts or greater.
6. Transmission fluid temperature (TFT) is -7 to +120°C (19-248°F).

P0872

The TCM detects that the TFP switch 3 signal voltage remains LOW after the 2-6 clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 18 counts are accumulated.

P0873

The TCM detects that the TFP switch 3 signal voltage remains HIGH after the 2-6 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 20 counts are accumulated.

1. DTCs P0872 and P0873 are Type C DTCs.
2. TCM freezes transmission adaptive functions for the 2-6 clutch.

DTCs P0872 and P0873 are Type C DTCs.

A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation) for control solenoid valve assembly

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Engine idling in Park with parking brake applied, and drive wheels chocked.
2. Verify with a scan tool the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If parameter values are correct for all gear ranges
3. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for each forward range with the gear select lever in Drive, using the scan tool to command all forward ranges. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If parameter values are correct for all gear ranges
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF. Remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
3. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
4. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil. If any TFP Switch parameter does not change states Replace the Q8 control solenoid valve assembly. If all TFP Switch parameters change states
5. Inspect the channel plate, spacer plate, and filter plate for debris and blocked orifices.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, or programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission Fluid Pressure Switch 1

Transmission Fluid Pressure Switch 3

Transmission Fluid Pressure Switch 4

Transmission Fluid Pressure Switch 5

The transmission fluid pressure (TFP) switch 4 is part of the control solenoid valve assembly which has no serviceable components. The transmission control module (TCM) supplies a signal circuit to the TFP switch 4. The TFP switch 4 has an internal case ground. TFP switch 4 is normally closed or LOW. When oil pressure is present at the TFP switch 4, the switch is open or HIGH. The normally LOW pressure control solenoid 5 controls pressure to the 1-2-3-4 clutch regulator valve. The TCM monitors the TFP switch 4 to determine the position of the 1-2-3-4 clutch regulator valve. When the 1-2-3-4 clutch is commanded OFF, pressure is present on the TFP switch 4. When the 1-2-3-4 clutch is commanded ON, the 1-2-3-4 clutch regulator valve moves and pressure to the TFP switch 4 is exhausted through the 1-2-3-4 clutch regulator valve.

P0877 or P0878

1. DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.
2. High side driver is enabled.
3. Engine speed is 400 RPM or greater for 5.0 seconds.
4. Engine speed is 550 RPM or greater.
5. Ignition voltage is 8.6 volts or greater.
6. Transmission fluid temperature (TFT) is -7 to +120°C (19-248°F).

P0877

The TCM detects that the TFP switch 4 signal voltage remains LOW after the 1-2-3-4 clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 5 counts are accumulated.

P0878

The TCM detects that the TFP switch 4 signal voltage remains HIGH after the 1-2-3-4 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 8 counts are accumulated.

1. DTCs P0877 and P0878 are Type C DTCs.
2. TCM freezes transmission adaptive functions for the 1-2-3-4 clutch.

DTCs P0877 and P0878 are Type C DTCs.

A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation) for control solenoid valve assembly

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Engine idling in Park with parking brake applied, and drive wheels chocked.
2. Verify with a scan tool the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
3. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for each forward range with the gear select lever in Drive, using the scan tool to command all forward ranges. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF. Remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
3. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
4. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil. If any TFP Switch parameter does not change states Replace the Q8 control solenoid valve assembly. If all TFP Switch parameters change states
5. Inspect the channel plate, spacer plate, and filter plate for debris and blocked orifices.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, or programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The line pressure control solenoid is part of the control solenoid valve assembly, which has no serviceable components. The normally high line pressure control solenoid regulates and directs oil pressure to the pressure regulator valve and isolator valve. Increasing pressure to the pressure regulator valve increases transmission line pressure. The transmission control module (TCM) varies the current to the line PC solenoid through a low side driver. Decreasing the current to the line PC solenoid increases line PC solenoid oil pressure by closing OFF the solenoid exhaust port. Increasing the current to the line PC solenoid decreases line PC oil pressure by opening the solenoid exhaust port. Line PC solenoid power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuit and components from excessive current flow. If excessive current flow is detected, the HSD will turn OFF. When the fault is corrected the HSD will reset. The transmission control module (TCM) varies the current to the line pressure control solenoid by controlling the amount of time the low side driver is ON and OFF. Decreasing the ON time, decreases the current to the line pressure control solenoid, which increases line pressure control solenoid oil pressure by closing OFF the solenoid exhaust port. Increasing the current to the line pressure control solenoid decreases line pressure control oil pressure by opening the solenoid exhaust port. Line pressure control solenoid power is supplied by the TCM through a high side driver. The high side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high side driver will reset.

1. Engine speed is 400-7500 RPM for 5 seconds.
2. Ignition voltage is 8.6-32 V.

P0961

TCM detects an internal electrical malfunction of the line pressure control solenoid where the measured line pressure control solenoid current does not equal the commanded line pressure control solenoid current for 5 seconds.

P0962

TCM detects a short to ground on the line pressure control solenoid control circuit for 2 seconds.

P0963

TCM detects an open or a short to voltage on the line pressure control solenoid control circuit for 5 seconds.

P0961 or P0963

1. DTCs P0961 and P0963 are Type B DTCs.
2. TCM freezes transmission adaptive functions.
3. TCM commands maximum line pressure.

P0962

1. DTC P0962 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd or 5th gear operation.
3. TCM inhibits the torque converter clutch (TCC).
4. TCM commands maximum line pressure.
5. TCM freezes transmission adaptive functions.
6. TCM turns the high side driver OFF.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.
9. TCM enables torque management.

1. DTCs P0961 and P0963 are Type B DTCs.
2. DTC P0962 is a Type A DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Engine running, transmission in park. Move the gear shift lever into each gear position and back into park position.
2. Verify the scan tool parameters listed below do not display Malfunction: Line Pressure Control Solenoid Valve Performance Test Status Line Pressure Control Solenoid Valve Control Circuit Low Voltage Test Status Line Pressure Control Solenoid Valve Control Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
4. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
5. All OK.

1. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris and clean as necessary. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If contaminated Repair as necessary. If not contaminated
3. Verify the resistance of each solenoid is within the specified range for listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid Valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT-47825-20 adapter harness between the vehicle harness connector and the Q8 Control Solenoid Valve Assembly connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: Line Pressure Control Solenoid Valve Performance Test Status Line Pressure Control Solenoid Valve Control Circuit Low Voltage Test Status Line Pressure Control Solenoid Valve Control Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 Control Solenoid Valve Assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Pressure control solenoid 2 is part of the control solenoid valve assembly which has no serviceable components. The normally high pressure control solenoid 2 regulates and directs oil pressure to the 3-5 reverse clutch regulator valve. Increasing pressure to the 3-5 reverse clutch regulator valve increases pressure to the 3-5 reverse clutch. The transmission control module (TCM) varies the current to the pressure control solenoid 2 by controlling the amount of time the low side driver is ON and OFF. Decreasing the current to the pressure control solenoid 2 increases pressure control solenoid 2 oil pressure by closing OFF the solenoid exhaust port. Increasing the current to the pressure control solenoid 2 decreases pressure control solenoid 2 oil pressure by opening the solenoid exhaust port. Power to pressure control solenoid 2 is supplied by the TCM through a high side driver. The high side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high side driver will reset.

P0965

1. DTC P0965 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0966

1. DTC P0966 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0967

1. DTC P0967 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0965

TCM detects an internal electrical performance malfunction of the pressure control solenoid 2 control circuit where the measured pressure control solenoid 2 current does not equal the commanded pressure control solenoid 2 current for 5 seconds.

P0966

TCM detects a short to ground on the pressure control solenoid 2 control circuit for 1 second.

P0967

TCM detects an open or short to voltage on the pressure control solenoid 2 control circuit for 1 second.

P0965

1. DTC P0965 is a Type C DTC.
2. TCM freezes transmission adaptive functions on the 3-5-Reverse clutch.

P0966

1. DTC P0966 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd or 5th gear operation.
3. TCM commands maximum line pressure.
4. TCM freezes transmission adaptive functions.
5. TCM turns the high side driver OFF.
6. TCM forces the torque converter clutch (TCC) OFF.
7. TCM inhibits Tap Up/Down function.
8. TCM inhibits manual shifting of forward gears.
9. TCM enables torque management.

P0967

1. DTC P0967 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd gear operation.
3. TCM commands maximum line pressure.
4. TCM freezes transmission adaptive functions.
5. TCM inhibits Tap Up/Down function.
6. TCM inhibits manual shifting of forward gears.

1. DTC P0965 is a Type C DTC.
2. DTCs P0966 and P0967 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature, then operate the vehicle in park for 5 seconds.
2. Operate the vehicle in Drive range. Allow the transmission to shift through all forward gear ranges.
3. Verify the scan tool parameters listed below do not display Malfunction: Pressure Control Solenoid Valve 2 Performance Test Status Pressure Control Solenoid Valve 2 Control Circuit Low Voltage Test Status Pressure Control Solenoid Valve 2 Control Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
6. All OK.

1. Ignition OFF, remove the Q8 control solenoid valve assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris and clean as necessary. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If contaminated Repair as necessary. If not contaminated
3. Verify the resistance is within the specified range for each solenoid listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid Valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT-47825-20 adapter harness between the vehicle harness connector and the Q8 Control Solenoid Valve Assembly connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: Pressure Control Solenoid Valve 2 Performance Test Status Pressure Control Solenoid Valve 2 Control Circuit Low Voltage Test Status Pressure Control Solenoid Valve 2 Control Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 control solenoid valve assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Pressure control solenoid 3 is part of the control solenoid valve assembly which has no serviceable components. The normally high pressure control solenoid 3 regulates and directs oil pressure to the R1/4-5-6 regulator valve. Increasing pressure control solenoid 3 pressure increases pressure to the low and reverse clutch or 4-5-6 clutch, depending on the position of the clutch select valve 2. The transmission control module (TCM) varies current to pressure control Solenoid 3 by controlling the time the low side driver is ON and OFF. Decreasing the current to pressure control solenoid 3 increases oil pressure by closing off the solenoid exhaust port. Increasing the current to the pressure control solenoid 3 decreases oil pressure by opening the exhaust port. Power is supplied to the pressure control solenoid 3 by the TCM through a high side driver. The high side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high side driver will reset.

P0969

1. DTC P0969 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0970

1. DTC P0970 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0971

1. DTC P0971 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0969

TCM detects an internal electrical performance malfunction of the clutch pressure control solenoid 3 control circuit where the measured clutch pressure control solenoid 3 currents does not equal the commanded clutch pressure control solenoid 3 current for 5 seconds.

P0970

TCM detects a short to ground on the clutch pressure control solenoid 3 control circuit for 1 second.

P0971

TCM detects an open or short to voltage on the clutch pressure control solenoid 3 control circuit for 1 second.

P0969

1. DTC P0969 is a Type C DTC.
2. TCM freezes transmission adaptive functions to the low and reverse clutch and 4-5-6 clutch.

P0970 or P0971

1. DTCs P0970 and P0971 are Type A DTCs.
2. TCM limits the transmission to Reverse and 3rd or 5th gear operation.
3. TCM inhibits the torque converter clutch (TCC).
4. TCM commands maximum line pressure.
5. TCM freezes transmission adaptive functions.
6. TCM turns the high side driver OFF.
7. TCM enables torque management.
8. TCM inhibits Tap Up/Down function.
9. TCM inhibits manual shifting of forward gears.

1. DTC P0969 is a Type C DTC.
2. DTCs P0970 and P0971 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature, then operate the vehicle in park for 5 seconds.
2. Operate the vehicle in Drive range. Allow the transmission to shift through all forward gear ranges.
3. Verify the scan tool parameters listed below do not display Malfunction: Pressure Control Solenoid Valve 3 Performance Test Status Pressure Control Solenoid Valve 3 Control Circuit Low Voltage Test Status Pressure Control Solenoid Valve 3 Control Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
6. All OK.

1. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris and clean as necessary. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If contaminated Repair as necessary. If not contaminated
3. Verify the resistance is within the specified range for each solenoid listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid Valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT-47825-20 adapter harness between the vehicle harness connector and the Q8 Control Solenoid Valve Assembly connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: Pressure Control Solenoid Valve 3 Performance Test Status Pressure Control Solenoid Valve 3 Control Circuit Low Voltage Test Status Pressure Control Solenoid Valve 3 Control Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 Control Solenoid Valve Assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Shift solenoid 1 is part of the control solenoid valve assembly, which has no serviceable components. Shift Solenoid 1 is a normally closed (NC) ON/OFF solenoid and is controlled by the transmission control module (TCM) through a low side driver. When the shift solenoid 1 is energized (ON), shift solenoid 1 fluid pressure is directed to the clutch select valve 2, which allows the valve to overcome the spring pressure and move to the applied position. Power to the shift solenoid 1 is supplied by the TCM through a high side driver. The high side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high side driver will reset.

P0973

1. DTC P0973 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0974

1. DTC P0974 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0973

TCM detects a short to ground on the shift solenoid 1 control circuit for 2 seconds.

P0974

TCM detects an open or a short to power on the shift solenoid 1 control circuit for 2 seconds.

P0973

1. DTC P0973 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd gear operation.
3. TCM commands maximum line pressure.
4. TCM freezes transmission adaptive functions.
5. TCM inhibits Tap Up/Down function.
6. TCM inhibits manual shifting of forward gears.
7. TCM inhibits auto grade braking

P0974

1. DTC P0974 is a Type B DTC.
2. TCM inhibits 1st gear.

1. DTC P0973 is a Type A DTC.
2. DTC P0974 is a Type B DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature, then operate the vehicle in Park for 5 seconds.
2. Place the gear selector in Reverse for 5 seconds and then idle the engine with the gear selector in Park for 5 seconds.
3. Verify the scan tool parameters listed below do not display Malfunction. Shift Solenoid Valve 1 Control Circuit Low Voltage Test Status Shift Solenoid Valve 1 Control Circuit Open Test Status Shift Solenoid Valve 1 Control Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
6. All OK.

1. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris and clean as necessary. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If contaminated Repair as necessary. If not contaminated
3. Verify the resistance is within the specified range for each solenoid listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid Valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT-47825-20 adapter harness between the vehicle harness connector and the Q8 Control Solenoid Valve Assembly connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: Shift Solenoid Valve 1 Control Circuit Low Voltage Test Status Shift Solenoid Valve 1 Control Circuit Open Test Status Shift Solenoid Valve 1 Control Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 Control Solenoid Valve Assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Shift solenoid 2 is part of the control solenoid valve assembly, which has no serviceable components. Shift solenoid 2 is a normally closed ON/OFF solenoid and is controlled by the transmission control module (TCM) through a low side driver. When the shift solenoid 2 is energized, fluid pressure is directed to the clutch select valve 3, which allows the valve to overcome the spring pressure and move to the applied position. Power to the shift solenoid 2 is supplied by the TCM through a high side driver. The high side driver protects the circuit and components from excessive current flow. If excessive current flow is detected, the high side driver will turn OFF. When the fault is corrected, the high side driver will reset.

P0976

1. DTC P0976 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0977

1. DTC P0977 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.

P0976

TCM detects a short to ground on the shift solenoid 2 control circuit for 2 seconds.

P0977

TCM detects an open or short to power on the shift solenoid 2 control circuit for 2 seconds.

P0976

1. DTC P0976 is a Type C DTC.
2. TCM freezes transmission adaptive functions.

P0977

1. DTC P0977 is a Type A DTC.
2. TCM limits the transmission to Reverse and 3rd gear operation.
3. TCM commands maximum line pressure.
4. TCM freezes transmission adaptive functions.
5. TCM inhibits Tap Up/Down function
6. TCM inhibits manual shifting of forward gears

1. DTC P0976 is a Type C DTC.
2. DTC P0977 is a Type A DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in 3rd gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature.
2. Place the gear selector in reverse for 5 seconds and then idle the engine with the gear selector in park for 5 seconds.
3. Verify the scan tool parameters listed below do not display Malfunction: Shift Solenoid Valve 2 Control Circuit Low Voltage Test Status Shift Solenoid Valve 2 Control Circuit Open Test Status Shift Solenoid Valve 2 Control Circuit High Voltage Test Status If Malfunction is displayed Refer to Circuit/System Testing below. If Malfunction is not displayed
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
5. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
6. All OK.

1. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
2. Verify the Q8 Control Solenoid Valve Assembly is not contaminated with any debris and clean as necessary. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If contaminated Repair as necessary. If not contaminated
3. Verify the resistance is within the specified range for each solenoid listed in the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . If the resistance is not within range Replace the Q8 Control Solenoid valve Assembly. If the resistance is within range
4. Place the Q8 Control Solenoid Valve Assembly on a clean work surface near the transmission assembly.
5. Connect the DT-47825-20 adapter harness between the vehicle harness connector, and the Q8 Control Solenoid Valve Assembly connector. Ignition ON.
6. Verify the scan tool parameters listed below do not display Malfunction: Shift Solenoid Valve 2 Control Circuit Low Voltage Test Status Shift Solenoid Valve 2 Control Circuit Open Test Status Shift Solenoid Valve 2 Control Circuit High Voltage Test Status If Malfunction is displayed Replace the Q8 Control Solenoid Valve Assembly. If Malfunction is not displayed
7. All OK.

Perform the Diagnostic Repair Verification after completing the repairs.

Note. Perform the Reset Transmission Adapts following all transmission repairs. Control Solenoid Valve and Transmission Control Module Assembly Replacement . Control Module References for control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Transmission Fluid Pressure Switch 1

Transmission Fluid Pressure Switch 3

Transmission Fluid Pressure Switch 4

Transmission Fluid Pressure Switch 5

The transmission fluid pressure (TFP) switch 5 is part of the control solenoid valve assembly, which has no serviceable components. The transmission control module (TCM) supplies a signal circuit to the TFP switch 5. The TFP switch 5 has an internal case ground. TFP switch 5 is normally closed or LOW. When oil pressure is present at the TFP switch 5, the switch is open or HIGH. The normally high pressure control (PC) solenoid 3 controls pressure to the R1/4-5-6 clutch regular valve. The TCM monitors the TFP switch 5 signal circuit to determine the position of the R1/4-5-6 clutch regulator valve. When the low and reverse clutch and 4-5-6 clutch are commanded OFF, pressure is present on the TFP switch 5. When the low and reverse clutch or the 4-5-6 clutch is commanded ON, the R1/4-5-6 clutch regulator valve moves and pressure to the TFP switch 5 is exhausted through the R1/4-5-6 clutch regulator valve.

DTC P0989 or P0990

1. DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P182E, or P1915 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Engine speed is 550 RPM or greater.
4. Ignition voltage is 8.6 volts or greater.
5. Transmission fluid temperature (TFT) is -7 to +120°C (19-248°F).
6. High side driver (HSD) is enabled.
7. Gear Selector is in a forward range.

P0989

The TCM detects that the TFP switch 5 signal voltage remains LOW after the low and reverse clutch or the 4-5-6 clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 18 counts are accumulated.

P0990

The TCM detects that the TFP switch 5 signal voltage remains HIGH after the low and reverse clutch or the 4-5-6 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 15 counts are accumulated.

1. DTCs P0989 and P0990 are Type C DTCs.
2. TCM freezes transmission adaptive functions for the reverse and low clutch and the 4-5-6 clutch.

DTCs P0989 and P0990 are Type C DTCs.

A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.

Schematic Reference

Automatic Transmission Controls Schematics

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation) for control solenoid valve assembly

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Engine idling in Park with parking brake applied, and drive wheels chocked.
2. Verify with a scan tool the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
3. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for each forward range with the gear select lever in Drive, using the scan tool to command all forward ranges. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) If any parameter value is not correct for a given gear range Refer to Circuit/System Testing below. If the parameter values are correct for all gear ranges
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF. Remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
3. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
4. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil. If any TFP Switch parameter does not change states Replace the Q8 control solenoid valve assembly. If all TFP Switch parameters change states
5. Inspect channel plate, spacer plate, and filter plate for debris and blocked orifices.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, or programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

To improve vehicle shift feel, the transmission control module (TCM) is constantly sending the engine control module (ECM) serial data messages with information regarding its request for modifying engine speed or torque. The ECM sets this code when it detects a discrepancy in the structure of this message causing its integrity to be questioned.

An intermittent fault in the controller area network (CAN) circuits will cause DTC P150C to set.

Engine is running.

ECM detects greater than 2 message count errors.

1. ECM disables engine speed and torque requests from TCM.
2. DTC P150C is a type B DTC.

DTC P150C is a type B DTC.

Description and Operation

Data Link Communications Description and Operation

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. DTC P150C is an informational DTC. Diagnose all other K20 Engine Control module DTCs prior to DTC P150C. If other K20 engine control module DTCs are set Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If no other K20 engine control module DTCs are set Diagnosis is accomplished by looking for an intermittent CAN circuit fault. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#data-communications-system) .
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The shift solenoid (SS) 1 is part of the control solenoid valve assembly, which has no serviceable components. SS 1 provides fluid pressure to control the operation of the clutch select valve 2, which is located in the control valve lower body assembly. SS 1, in conjunction with clutch select valve 2, controls the pressure path to the reverse and low clutch and 4-5-6 clutch. A diagnostic test is performed by the transmission control module (TCM) to determine the state of the clutch select valve 2. During this diagnostic test, the TCM commands the SS 1 ON, supplying pressure to move the clutch select valve 2 toward its spring. At the same time, line pressure is elevated slightly to assist the spring side pressure. If the spring is broken, or the clutch select valve 2 cannot move due to another mechanical condition, the DTC will set.

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, P0741, P0742, P1751, P2763, or P2764 is not set.
2. Current commanded range is not Neutral, Reverse, or 1st gear.
3. The gear ratio is between 0.69-3.07.
4. The engine speed is 400 RPM or greater for 5 seconds.
5. The ignition voltage is 8.6 volts or greater.
6. The transmission fluid temperature (TFT) is -7 to +130°C (19-266°F).
7. The throttle position is 8 percent or greater.
8. The engine torque is 80 N.m (59 lb ft) or greater.
9. The engine speed is 500 RPM or greater.
10. The vehicle speed is 16 km/h (10 mph) or greater.
11. No upshift or downshift in process.
12. The engine torque signal is valid.
13. The throttle position signal is valid.
14. The torque converter clutch (TCC) is commanded OFF.

The TCM detects attained gear slip is 100 RPM or greater for 1 second.

DTC P1751 is a Type B DTC.

DTC P1751 is a Type B DTC.

Before performing a road test, configure and setup the scan tool for snapshot mode. This will allow you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.

Description and Operation

Transmission General Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Perform the «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) to verify correct fluid level and condition.
3. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . Verify the transmission operation performs as indicated in the road test instructions.
4. Review the scan tool snapshot transmission data parameters. Verify the engine and transmission data parameters display the correct values in all forward gear ranges: Engine Speed Transmission ISS Transmission OSS Shift Solenoid Valve 1 Gear Command
5. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Perform the «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . Verify the transmission line pressure gauge is within the range specified in the Line PC Solenoid Valve Pressure table. Refer to «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If not within the specified ranges, refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) .
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . If the Q8 control solenoid valve assembly does not pass the performance test, replace the Q8 control solenoid valve assembly.
4. Listed in the chart below, are conditions for each component that could set DTC P1751. Carefully inspect each component for that condition. Repair or replace as necessary.

Note. Perform the Reset Transmission Adapts following all transmission related repairs.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Valve Upper Body Assembly Cleaning and Inspection

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

When the shift lever is placed left of the D position, the driver shift request (DSR), also known as the tap shift function, is activated. The DSR allows the vehicle operator to shift gears by pushing the shift lever forward for an upshift or pulling the shift lever rearward for a downshift. The BCM supplies battery voltage, ground and a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is left of the position, then pushed forward for an upshift, or pulled rearward for a downshift, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module to perform the upshift or downshift. The TCM is constantly monitoring the serial data sent from the BCM for the correct number and sequence of counts for Tap Up and Tap Down function.

1. Tap Up and Tap Down message health is received from the BCM.
2. Engine speed is 400 RPM or greater for 5 seconds.

TCM detects an error in the rolling count value that does not match with the BCM count, 3 times within 10 seconds.

1. DTC P1761 is a Type C DTC.
2. TCM inhibits Tap Up/Down function.
3. TCM inhibits manual shifting of forward gears.

DTC P1761 is a Type C DTC.

Schematic Reference

1. «Automatic Transmission Controls Schematics»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-wiring-schematic-diagrams)
2. «Data Communication Schematics»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#data-communications-system)
3. «Body Control System Schematics»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#data-communications-system)

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Electronic Component Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. DTC P1761 is an informational DTC. Diagnose all other body control module DTCs prior to DTC P1761. If other body control module DTCs are set Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) If no other body control module DTCs are set
2. Diagnosis is accomplished by looking for an intermittent CAN circuit fault. Refer to «Scan Tool Does Not Communicate with Chassis High Speed GMLAN Device»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#data-communications-system) .
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission related repairs.
2. Perform the «Diagnostic Repair Verification»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-repair-verification) after completing the diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Internal Mode Switch A/B/C/P

The manual shift detent lever with shaft position switch assembly, or internal mode switch assembly, is a sliding contact switch attached to the manual shift detent lever within the transmission. The 4 inputs to the transmission control module (TCM), from the switch, indicate the position selected by the transmission manual shaft. The input voltage at the TCM is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as the internal mode switch A/B/C/P parameter. The internal mode switch input parameters represented are transmission range Signal A, Signal B, Signal C, and Signal P.

The park/neutral position switch is integrated into the transmission internal mode switch. The circuit uses the TCM as a pass-through connector only.

The park/neutral signal is sent from the park/neutral switch directly to the engine control module (ECM) and is used for engine start enable.

P182E

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, or P0723 is not set.
2. Engine speed is 400-7500 RPM for 5 seconds.
3. Ignition voltage is 8.6-32 V.
4. Engine torque signal is valid.

P1915

1. DTC P0722, P0723, or P1915 is not set.
2. Transmission output shaft speed is 90 RPM or less.
3. Ignition voltage was 5 V or greater, and has not dropped below 2 V.

P182E

Internal mode switch does not indicate a valid Park, Reverse, Neutral or Drive Range gear position for 7 seconds.

P1915

Internal mode switch does not indicate Park or Neutral during the following sequence

1. Engine speed is 50 RPM or less for 0.25 seconds or greater.
2. Engine speed is 50-480 RPM for 0.07 seconds or greater.
3. Engine speed is 525 RPM or greater and the transmission input speed is 200 RPM or greater for 1.25 seconds.

1. DTCs P182E and P1915 are Type A DTCs.
2. TCM commands maximum line pressure.
3. TCM forces the torque converter clutch (TCC) OFF.
4. TCM turns all the solenoids OFF.
5. TCM freezes transmission adaptive functions.
6. TCM limits the transmission to Reverse and 5th gear operation.
7. Torque management is enabled.
8. TCM turns the high side driver OFF.
9. TCM inhibits Tap Up/Down function.
10. TCM inhibits manual shifting of forward gears.

DTCs P182E and P1915 are Type A DTCs.

Under certain driving conditions, DTC P182E could set due to an intermittent low voltage fault on the park/neutral signal circuit, before conditions for setting DTC P0851 are met. Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Transmission Component and System Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-component-and-system-description)
3. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Verify the range selector lever cable is adjusted correctly. Refer to «Range Selector Lever Cable Adjustment»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle__range-selector-lever-cable-adjustment) . If cable adjustment is not correct Repair as necessary. If cable adjustment is correct
2. Ignition ON.
3. Verify the scan tool transmission control module Internal Mode Switch A/B/C/P parameter matches the «Transmission Internal Mode Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-internal-mode-switch-logic) table for each gear shift lever position. If the parameter does not match Refer to Circuit/System Testing below. If the parameter matches
4. Verify the scan tool engine control module Park/Neutral Position Switch parameter displays Park/Neutral with the gear shift lever in Park or Neutral and In Gear when in Reverser or Drive. If Park/Neutral or In Gear is not displayed Refer to Circuit/System Testing below. If Park/Neutral and In Gear is displayed
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing below. If the DTC does not set
7. All OK.

1. Ignition OFF, remove the control valve body cover.
2. Connect the vehicle harness connector to the Q8 Control Solenoid Valve Assembly.
3. Disconnect the B15 Transmission Internal Mode Switch connector at the Q8 Control Solenoid Valve Assembly.
4. Ignition ON.
5. Verify the scan tool transmission control module Internal Mode Switch A/B/C/P parameter displays High High. If High is not displayed Replace the Q8 control solenoid valve assembly. If High is displayed
6. Verify the scan tool engine control module Park/Neutral Position Switch parameter displays In Gear. If In Gear is not displayed Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the neutral start signal circuit and ground at the vehicle harness K20 Engine Control Module connector. If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K20 Engine Control Module If In Gear is displayed
7. Install a 3 A fused jumper wire between the low reference circuit terminal A and each signal circuit listed below one at a time at the Q8 Control Solenoid Valve Assembly. Signal A - terminal E Signal B - terminal D Signal C - terminal C Signal P - terminal B
8. Verify the scan tool TCM A/B/C/P displays 1 Low and 3 High when a signal circuit is grounded. If 1 Low and 3 High is not displayed Replace the Q8 control solenoid valve assembly. If 1 Low and 3 High is displayed
9. Connect a 3 A fused jumper wire between park/neutral switch signal circuit terminal F and low reference circuit terminal A at the Q8 Control Solenoid Valve Assembly.
10. Verify the scan tool engine control module Park/Neutral Position Switch parameter displays Park/Neutral. If Park/Neutral is not displayed Ignition OFF, disconnect the connector at the K20 Engine Control Module. Test for less than 2 ohms in the signal circuit end to end If 2 ohms or greater, repair the open/high resistance in the circuit If less than 2 ohms, replace the K20 Engine Control Module If Park/Neutral is displayed
11. Replace the B15 Transmission Internal Mode Switch.

Perform the Diagnostic Repair Verification after completing the repairs.

1. Perform the «Reset Transmission Adapts»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__reset-transmission-adapts) following all transmission repairs.
2. «Control Valve Body Cover Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
3. «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
4. «Manual Shift Detent Lever with Shaft Position Switch Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
5. «Range Selector Lever Cable Adjustment»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle__range-selector-lever-cable-adjustment)
6. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ECM or control solenoid valve assembly replacement, programming, and setup.

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

When the shift lever is moved left of the D position, the transmission will enter sport mode. With the shift lever in this position, the transmission will enter manual mode if the gear shift lever is pressed forward or rearward. This allows the operator to select an upshift by pressing the gear shift lever forward, and downshift by pressing the gear shift lever rearward. The body control module (BCM) supplies a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is left of the D position, a voltage drop occurs across the resistor network. When the gear shift lever is pressed forward or rearward, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module to perform the upshift or downshift.

1. DTC P0815, P0816, or P0826, P1825, P1915 or U0100 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 V or greater.

The Tap Up/Tap Down switch signal is Active when the IMS does not indicate L (M) for 2 seconds or greater 3 times during the same ignition cycle.

1. DTC P1876 is a Type C DTC.
2. TCM disables Tap shift functions.

DTC P1876 is a Type C DTC.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

1. «Transmission General Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation__transmission-general-description)
2. «Electronic Component Description»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-description-and-operation)

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON.
2. Verify with a scan tool there are no transmission internal mode switch (IMS) DTCs set. If IMS DTCs were set Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) . If no IMS DTCs were set
3. Verify the gear shift lever position matches the scan tool TCM Internal Mode Switch parameter while slowly moving the gear shift lever from Park through all ranges. If the displayed values are not correct Refer to «Range Selector Lever Cable Adjustment»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle__range-selector-lever-cable-adjustment) . If the displayed values are correct
4. Verify the scan tool Driver Shift Control Mode parameter displays Inactive with the transmission shift lever in Park, Reverse, Neutral, and Drive, and Active with the shift lever left of the D or manual mode position. If the Driver Shift Mode parameter does not display the correct values Refer to Circuit/System Testing below. If the Driver Shift Mode parameter displays the correct values
5. Shift lever left of the D position.
6. Verify the scan tool Up and Down Shift Switch parameter changes from None to Upshift when the tap up button is pressed, and from None to Downshift when the tap down button is pressed. If parameter values are not correct Refer to Circuit/System Testing below. If parameter values are correct
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, disconnect the harness connector from the S3 transmission shift lever. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the S3 transmission shift lever harness connector terminal 2 and ground. If 10 ohms or greater Ignition OFF. Test the ground circuit for less than 2 ohms end to end. If greater than 2 ohms, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
3. Ignition ON.
4. Verify the scan tool Driver Shift Control parameter displays inactive. If Driver Shift Control Parameter does not display Inactive Ignition OFF, disconnect the harness connector at the K9 body control module. Test for infinite resistance between the transmission shift lever vehicle harness connector signal circuit terminal 3 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K9 body control module. If Driver Shift Control Parameter displays Inactive
5. Verify a test lamp illuminates between the S3 transmission shift lever harness connector ignition circuit terminal 1 and ground circuit terminal 2. If the test lamp does not illuminate Ignition OFF. Test for less than 2 ohms in the ignition circuit end to end. If 2 ohms or greater, repair the ignition circuit. If less than 2 ohms, replace the K9 body control module. If the test lamp illuminates
6. Test for 11 V or greater at the S3 transmission shift lever harness connector between signal circuit terminal 3 and ground. If less than 11 V Ignition OFF, disconnect the connector at the K9 body control module. Test for less than 2 ohms in the signal circuit wire end to end. If 2 ohms or greater, repair the open/high resistance in the signal circuit wire. If less than 2 ohms, replace the K9 body control module. If 11 V or greater
7. Ignition OFF, connect the S3 transmission shift lever harness connector, ignition ON.
8. Test for 11 V or greater between the S3 transmission shift lever connector terminal 3 and ground in the park, reverse, neutral, and drive gear select lever positions by back probing the connector. If less than 11 V Replace the S3 transmission shift lever. If 11 V or greater
9. Shift selector lever left of the D position.
10. Test for 8.0-10.6 V between the S3 transmission shift lever connector terminal 3 and ground. If not between 8.0-10.6 V Ignition OFF. Test the signal circuit for less than 2 ohms end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the S3 shift lever. If between 8.0-10.6 V
11. Test for 5.1-7.3 V between the S3 transmission shift lever connector terminal 3 and ground with the shift lever pressed forward. If not between 5.1-7.3 V Ignition OFF. Test the signal circuit for less than 2 ohms end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the S3 shift lever. If between 5.1-7.3 V
12. Test for 2.0-4.6 V between the S3 transmission shift lever connector terminal 3 and ground with the shift lever pressed rearward. If not between 2.0-4.6 V Ignition OFF. Test the signal circuit for less than 2 ohms end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the S3 shift lever. If between 2.0-4.6 V
13. Replace the K9 body control module.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Transmission Control Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) for AT TAP shift switch replacement
2. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for body control module (BCM) or control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The clutch pressure control (PC) solenoid 4 is part of the control solenoid valve assembly which has no serviceable components. The PC solenoid 4 regulates transmission fluid pressure to the 2-6 clutch regulator valve which controls pressure to the 2-6 clutch. The transmission control module (TCM) calculates gear ratio based on the RPM signals from the input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.

P2714

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. Output speed is 36 RPM or greater, or throttle position is 0.5 percent or greater.
4. Throttle position signal is valid.
5. Engine speed is 400 RPM or greater for 5 seconds.
6. Transmission fluid temperature is -7°C (19°F) or greater.
7. High side driver (HSD) is enabled.

P2715

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. HSD is enabled.
4. Transmission fluid temperature is -7°C (19°F) or greater.
5. Engine speed is 400 RPM or greater for 5 seconds.
6. Transmission output shaft speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
7. Commanded and attained range is not 1st gear.

P2714

TCM has detected an incorrect gear ratio or neutral condition when the 2-6 clutch is commanded ON. This condition must occur 3 times.

P2715

TCM has detected an incorrect gear ratio change when the 2-6 clutch is commanded OFF during a shift or, when 2nd gear ratio is detected in 1st gear. This condition must occur 3 times.

P2714

1. DTC P2714 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM inhibits Tap Up/Down function.
4. TCM inhibits manual shifting of forward gears.
5. TCM freezes transmission adaptive functions.
6. TCM limits the transmission to Reverse and 3rd gear operation.

P2715

1. DTC P2715 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM inhibits Tap Up/Down function.
4. TCM inhibits manual shifting of forward gears.
5. TCM freezes transmission adaptive functions.
6. TCM limits the transmission to Reverse and 2nd gear operation.

DTCs P2714 and P2715 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Verify correct transmission fluid level and condition. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
3. Verify with a scan tool the Transmission Fluid Pressure Switch 3 parameter values are correct for the Park, Reverse, and Neutral gear selector positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 3 Refer to Circuit/System Testing below. If TFP switch 3 values are correct
4. Place the gear select lever in Drive range. Verify the Transmission Fluid Pressure Switch 3 parameter states are correct for all forward ranges when commanded with a scan tool. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 3 Refer to Circuit/System Testing below. If TFP switch 3 values are correct
5. Ignition ON, clear the TCM DTCs
6. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . Verify the transmission operation performs as indicated in the road test instructions and DTC P2714 or P2715 did not set. If DTC P2714 or P2715 sets Refer to Circuit/System Testing below. If DTC P2714 or P2715 did not set
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Verify the transmission line pressures are within the ranges specified in the Line PC Solenoid Valve Pressure table. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If line pressures are not within the specified ranges Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) . If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid valve. If a pressure change does not occur for each solenoid Replace the Q8 control solenoid valve assembly. If a pressure change occurs for each solenoid
4. Listed in the table below, are conditions for each component that could set DTC P2714 or P2715. Carefully inspect each component for that condition. Repair or replace as necessary.

DTC P2714 or P2715

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Valve Lower Body and Upper Body Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
2. «Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Pressure Control Solenoid Valve 4 Performance Test Status

Pressure Control Solenoid Valve 4 Control Circuit Low Voltage Test Status

Pressure Control Solenoid Valve 4 Control Circuit High Voltage Test Status

The clutch pressure control (PC) solenoid 4 is part of the control solenoid valve assembly which has no serviceable components. The normally low PC solenoid 4 regulates and directs oil pressure to the 2-6 clutch regulator valve. Increasing PC solenoid 4 pressure increases pressure to the 2-6 clutch regulator valve. The transmission control module (TCM) varies the current to the PC solenoid 4 through a low side driver. Increasing the current to PC solenoid 4 increases oil pressure by closing OFF the solenoid exhaust port. Decreasing the current to PC solenoid 4 decreases oil pressure by opening the exhaust port. PC solenoid 4 power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuit and components from excessive current flow. If excessive current flow is detected, the HSD will turn OFF. When the fault is corrected the HSD will reset.

P2719

1. Engine speed is 400 RPM or greater for 5 seconds.
2. Ignition voltage is 8.6 volts or greater.
3. DTC P2719 is not set.

P2720

1. Engine speed is 400 RPM or greater for 5 seconds.
2. Ignition voltage is 8.6 volts or greater.
3. DTC P2720 is not set.

P2721

1. Engine speed is 400 RPM or greater for 5 seconds.
2. Ignition voltage is 8.6 volts or greater.
3. DTC P2721 is not set.

P2719

TCM detects an internal electrical malfunction on the clutch PC solenoid 4 control circuit where the measured PC solenoid 4 current does not equal the commanded clutch PC solenoid 4 current for 5 seconds.

P2720

TCM detects a short to ground on the clutch PC solenoid 4 control circuit for 1 second.

P2721

TCM detects an open or short to voltage on the clutch PC solenoid 4 control circuit for 1 second.

P2719

1. DTC P2719 is a Type C DTC.
2. TCM freezes transmission adaptive functions on the 2-6 clutch.

P2720

1. DTC P2720 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM freezes transmission adaptive functions.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse and 2nd gear operation.

P2721

1. DTC P2721 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM freezes transmission adaptive functions.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse and 3rd gear operation.

1. DTC P2719 is a Type C DTC.
2. DTCs P2720 and P2721 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature, then operate the vehicle in Park for 5 seconds.
2. Operate the vehicle in Drive range. Allow the transmission to shift through all forward gear ranges. Verify with a scan tool the following test status parameters display OK: Pressure Control Solenoid Valve 4 Performance Test Status Pressure Control Solenoid Valve 4 Control Circuit High Voltage Test Status Pressure Control Solenoid Valve 4 Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Refer to Circuit/System Testing below. If all test status parameters display OK
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . The Q8 control solenoid valve assembly must be externally cleaned of all debris.
3. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
4. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
5. Ignition ON, verify with a scan tool the following test status parameters display OK: Pressure Control Solenoid Valve 4 Performance Test Status Pressure Control Solenoid Valve 4 Control Circuit High Voltage Test Status Pressure Control Solenoid Valve 4 Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Replace the Q8 control solenoid valve assembly. If all test status parameters display OK
6. All OK.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The clutch pressure control (PC) solenoid 5 is part of the control solenoid valve assembly which has no serviceable components. The clutch PC solenoid 5 regulates the transmission fluid pressure (TFP) to the 1-2-3-4 clutch regulator valve, which controls pressure to the 1-2-3-4 clutch. The transmission control module (TCM) calculates gear ratio based on the RPM signals from the input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the expected transmission gear ratio to the calculated gear ratio for each commanded gear.

P2723

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. High side driver (HSD) is enabled.
4. Output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
5. Throttle position signal is valid.
6. Engine speed is 400 RPM or greater for 5 seconds.
7. Transmission fluid temperature (TFT) is -7°C (19°F) or greater.

P2724

1. DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
2. Ignition voltage is 8.6 volts or greater.
3. HSD is enabled.
4. TFT is -7°C (19°F) or greater.
5. Output speed is 36 RPM or greater, or the throttle position is 0.5 percent or greater.
6. Engine speed is 400 RPM or greater for 5 seconds.

P2723

TCM has detected an incorrect gear ratio or neutral condition when the 1-2-3-4 clutch is commanded ON. This condition must occur 3 times.

P2724

TCM has detected an incorrect gear ratio change when the 1-2-3-4 clutch is commanded OFF during a shift. This condition must occur 3 times.

P2723

1. DTC P2723 is a Type A DTC.
2. TCM freezes transmission adaptive functions.
3. TCM commands maximum line pressure.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. Torque management is enabled.
7. TCM limits the transmission to Reverse and fifth gear operation.

P2724

1. DTC P2724 is a Type A DTC.
2. TCM freezes transmission adaptive functions.
3. TCM commands maximum line pressure.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse, first, or third gear operation.

DTCs P2723 and P2724 are Type A DTCs.

Before performing a road test, configure and setup the scan tool for snapshot mode. This will allow you to display, monitor, and verify multiple transmission data parameters at one time, after the road test.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine idling in Park, with parking brake applied and drive wheels chocked.
2. Verify correct transmission fluid level and condition. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
3. Verify with a scan tool the Transmission Fluid Pressure Switch 4 parameter values are correct for the Park, Reverse, and Neutral gear selector positions. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 4 Refer to Circuit/System below. If TFP switch 4 values are correct
4. Gear select lever in Drive range. Verify the Transmission Fluid Pressure Switch 4 parameter states are correct for all forward ranges when commanded with a scan too. Refer to «Transmission Fluid Pressure Switch Logic»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__transmission-fluid-pressure-switch-logic) . If not the correct values for TFP switch 4 Refer to Circuit/system below. If TFP switch 4 values are correct
5. Ignition ON, clear the DTCs from the TCM
6. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) . Verify the transmission operation performs as indicated in the road test instructions and DTC P2723 or P2724 did not set. If DTC P2723 or P2724 sets Refer to Circuit/System below. If DTC P2723 or P2724 did not set
7. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Verify the transmission line pressures are within the ranges specified in the Line PC Solenoid Valve Pressure table. Refer to «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) , and «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) . If line pressures are not within the specified ranges Refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) . If line pressures are within the specified ranges
2. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__control-solenoid-valve-and-transmission-control) . Test all solenoids on the Q8 control solenoid valve assembly. A pressure change should occur for each solenoid valve. If a pressure change does not occur for each solenoid Replace the Q8 control solenoid valve assembly. If a pressure change occurs for each solenoid
4. Listed in the table below, are conditions for each component that could set DTC P2723 or P2724. Carefully inspect each component for that condition. Repair or replace as necessary.

DTC P2723 or P2724

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Valve Lower Body and Upper Body Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle)
2. «Low and Reverse Clutch and 1-2-3-4 Clutch Plate Removal»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-off-vehicle)
3. «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Pressure Control Solenoid Valve 5 Performance Test Status

Pressure Control Solenoid Valve 5 Control Circuit Low Voltage Test Status

Pressure Control Solenoid Valve 5 Control Circuit High Voltage Test Status

The clutch pressure control (PC) solenoid 5 is part of the control solenoid valve assembly which has no serviceable components. The normally low PC solenoid 5 regulates and directs oil pressure to the 1-2-3-4 clutch regulator valve and 1-2-3-4 clutch boost valve. Increasing PC solenoid 5 pressure increases pressure to the 1-2-3-4 clutch. The transmission control module (TCM) varies the current to the PC solenoid 5 through a low side driver. Increasing the current to PC solenoid 5 increases oil pressure by closing OFF the solenoid exhaust port. Decreasing the current to PC solenoid 5 decreases oil pressure by opening the exhaust port. PC solenoid 5 power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuit and components from excessive current flow. If excessive current flow is detected, the HSD will turn OFF. When the fault is corrected, the HSD will reset.

P2728

1. DTC P2728 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.

P2729

1. DTC P2729 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.

P2730

1. DTC P2730 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.

P2728

TCM detects an internal electrical performance malfunction of the clutch PC solenoid 5 control circuit where the measured clutch PC solenoid 5 current does not equal the commanded clutch PC solenoid 5 current for 5 seconds.

P2729

TCM detects a short to ground on the clutch PC solenoid 5 control circuit for 1 second.

P2730

TCM detects an open or short to voltage on the clutch PC solenoid 5 control circuit for 1 second.

P2728

1. DTC P2728 is a Type C DTC.
2. TCM freezes transmission adaptive functions on the 1-2-3-4 clutch.

P2729

1. DTC P2729 is a Type A DTC.
2. TCM commands maximum line pressure.
3. TCM freezes transmission adaptive functions.
4. TCM inhibits Tap Up/Down function.
5. TCM inhibits manual shifting of forward gears.
6. TCM limits the transmission to Reverse, 1st and 3rd gear operation.

P2730

1. DTC P2730 is a Type A DTC.
2. TCM inhibits the TCC.
3. TCM forces the HSD OFF.
4. TCM commands maximum line pressure.
5. TCM freezes transmission adaptive functions.
6. TCM inhibits Tap Up/Down function.
7. TCM inhibits manual shifting of forward gears.
8. Torque management in enabled.
9. TCM limits the transmission to Reverse and 5th gear operation.

1. DTC P2728 is a Type C DTC.
2. DTCs P2729 and P2730 are Type A DTCs.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature, then operate the vehicle in Park for 5 seconds.
2. Operate the vehicle in Drive range. Allow the transmission to shift through all forward gear ranges. Verify with a scan tool the following test status parameters display OK: Pressure Control Solenoid Valve 5 Performance Test Status Pressure Control Solenoid Valve 5 Control Circuit High Voltage Test Status Pressure Control Solenoid Valve 5 Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Refer to Circuit/System Testing below. If all test status parameters display OK
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . The Q8 control solenoid valve assembly must be externally cleaned of all debris.
3. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
4. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
5. Ignition ON, verify with a scan tool the following test status parameters display OK: Pressure Control Solenoid Valve 5 Performance Test Status Pressure Control Solenoid Valve 5 Control Circuit High Voltage Test Status Pressure Control Solenoid Valve 5 Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Replace the Q8 control solenoid valve assembly. If all test status parameters display OK
6. All OK.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

TCC Pressure Control Solenoid Valve Control Circuit Status

TCC Pressure Control Solenoid Valve Control Circuit Low Voltage Test Status

TCC Pressure Control Solenoid Valve Control Circuit High Voltage Test Status

The torque converter clutch (TCC) pressure control (PC) solenoid is part of the control solenoid valve assembly which has no serviceable components. The normally low TCC PC solenoid regulates oil pressure to the TCC regulator valve and TCC control valve. Increasing TCC PC solenoid oil pressure increases oil pressure to the torque converter to apply the clutch. The transmission control module (TCM) varies the current to the TCC PC solenoid through a low side driver. Increasing current to the TCC PC solenoid increases oil pressure by closing OFF the solenoid exhaust port. Decreasing current to the TCC PC solenoid decreases oil pressure by opening up the solenoid exhaust port. The TCC PC solenoid power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuit and components from excessive current flow. If excessive current flow is detected, the HSD will turn OFF. When the fault is corrected, the HSD will reset.

P2762

1. DTC P2762 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.

P2763

1. DTC P0658, P0659, or P2763 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.
4. High side driver is enabled.

P2764

1. DTC P0658, P0659, or P2764 is not set.
2. Engine speed is 400 RPM or greater for 5 seconds.
3. Ignition voltage is 8.6 volts or greater.
4. High side driver is enabled.

P2762

TCM detects an internal electrical performance malfunction of the TCC PC solenoid control circuit where the measured TCC PC solenoid current does not equal the commanded TCC PC solenoid for 5 seconds.

P2763

TCM detects an open/high resistance or short to voltage on the TCC pressure solenoid control circuit for 5 seconds.

P2764

TCM detects a short to ground on the TCC pressure solenoid control circuit for 5 seconds.

P2762

DTC P2762 is a Type C DTC.

P2763

1. DTC P2763 is a Type B DTC.
2. TCM inhibits 6th gear.
3. TCM forces TCC OFF.
4. TCM commands the hot mode shift pattern.

P2764

1. DTC P2764 is a Type A DTC.
2. TCM inhibits TCC.
3. TCM freezes transmission adaptive functions.
4. TCM commands maximum line pressure.
5. TCM inhibits Tap Up/Down function.
6. TCM inhibits manual shifting of forward gears.
7. TCM limits the transmission to Reverse and 5th gear operation.
8. Torque management is enabled.
9. TCM commands the HSD OFF.

1. DTC P2762 is a Type C DTC.
2. DTC P2763 is a Type B DTC.
3. DTC P2764 is a Type A DTC.

Connector End View Reference

1. «COMPONENT CONNECTOR END VIEWS - INDEX»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-component-connector-end-views-index)
2. «Inline Harness Connector End Views»(/buick/lacrosse/ii-2009-2013/remont/body-electrical/#wiring-systems-and-power-management-inline-harness-connector-end-views)

Description and Operation

Transmission General Description

Electrical Information Reference

1. «Circuit Testing»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

1. Operate the vehicle in second gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature.
2. Operate the vehicle in Drive range and ensure TCC is commanded ON for 1 minute. Verify with a scan tool the following test status parameters display OK: TCC Pressure Control Solenoid Valve Control Circuit Status TCC Pressure Control Solenoid Valve Control Circuit High Voltage Test Status TCC Pressure Control Solenoid Valve Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Refer to Circuit/System Testing below. If all test status parameters display OK
3. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/lacrosse/ii-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) .

1. Ignition OFF, remove the Q8 control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
2. Perform the «Control Solenoid Valve and Transmission Control Module Assembly Inspection»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) . The Q8 control solenoid valve assembly must be externally cleaned of all debris.
3. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.
4. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.
5. Ignition ON, verify with a scan tool the following test status parameters display OK: TCC Pressure Control Solenoid Valve Control Circuit Status TCC Pressure Control Solenoid Valve Control Circuit High Voltage Test Status TCC Pressure Control Solenoid Valve Control Circuit Low Voltage Test Status If any test status parameter displays Fault or Malfunction Replace the Q8 control solenoid valve assembly. If all test status parameters display OK
6. All OK.

Note. Perform the Reset Transmission Adapts following all transmission related repairs. Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, and programming

Symptoms - Automatic Transmission

Note. Use the symptom tables only if the following conditions are met: Refer to Diagnostic Starting Point - Vehicle . There are no DTCs set. The control modules can communicate via the serial data link. Review the system operation in order to familiarize yourself with the system functions. Refer to Transmission General Description , and Transmission Component and System Description .

Visual/Physical Inspection

Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. Fluid Diagnosis «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) «Automatic Transmission Fluid Leaks»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__automatic-transmission-fluid-leaks) «Fluid Leak Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures)
2. Noise and Vibration Diagnosis «Whine/Growl Noise»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__whinegrowl-noise) «Noise and Vibration Analysis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__noise-and-vibration-analysis) «Torque Converter Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures)
3. Range Performance Diagnosis «No Park»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-park) «No Drive in All Ranges»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-drive-in-all-ranges) «No Reverse Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-reverse-gear)
4. Shift Quality Feel Diagnosis «Harsh Garage Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-garage-shift) «Harsh or Late First, Second, Third, and Fourth Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-or-late-first-second-third) «Harsh First and Reverse Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-first-and-reverse-shift) «Harsh or Late Second and Sixth Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-or-late-second-and-sixth) «Harsh or Late Third, Fifth, and Reverse Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-or-late-third-fifth-and) «Harsh Fourth, Fifth, and Sixth Shift»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__harsh-fourth-fifth-and-sixth-shift)
5. Shift Pattern «No First and Reverse Gears»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-first-and-reverse-gears) «No First, Second, Third, and Fourth Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-first-second-third-and-fourth) «No Second and Sixth Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-second-and-sixth-gear) «No Fourth, Fifth, and Sixth Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-fourth-fifth-and-sixth-gear) «No Third, Fifth, and Reverse Gear»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-third-fifth-and-reverse-gear)
6. Torque Converter Diagnosis «Torque Converter Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) «No Torque Converter Clutch Apply»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-torque-converter-clutch-apply) «No Torque Converter Clutch Release»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__no-torque-converter-clutch-release)
7. Symptom Not Found or No Symptom Detected «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) «Line Pressure Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures)

Scheme 77

1. Inspect the control solenoid valve assembly connectors and pins (1, 2, 4, 6) for the following conditions: Damage Bent pins Debris Broken retaining tab Contamination
2. Ensure no metallic debris is inside the connectors near the terminal pins.
3. Inspect the control solenoid valve assembly solenoid leads (3) for contamination or metallic debris.
4. Inspect the 4 control solenoid valve assembly filter plate retaining tabs (5) for cracks and ensure proper tension when filter plate is attached.

Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test

Special Tools

1. EL 35616 GM-Approved Terminal Test Kit
2. EL 38522 Variable Signal Generator

For equivalent regional tools, refer to Special Tools .

Scheme 78

The purpose of this test is to provide a simulated input/output speed sensor (ISS/OSS) signal to the control solenoid valve assembly ISS/OSS input circuits.

Transmission Input Speed Sensor

1. Ignition OFF, disconnect the ISS wiring harness connector X3 (1) from the control solenoid valve assembly.
2. Ignition ON, test for 8.3-9.3 volts at terminal A. If not within the specified range, replace the control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Ignition OFF, using the EL 35616 terminal test kit, connect the EL38522 variable signal generator red lead to the ISS signal circuit terminal B on the TCM.
4. Connect the black lead from the EL 38522 variable signal generator to ground.
5. Set the EL 38522 variable signal generator to 5 volts, the frequency to 300 Hz, and the percent duty cycle to 50 or the normal position.
6. Ignition ON, verify with a scan tool the Transmission ISS parameter is between 495-505 RPM.

1. If not within the specified range, replace the control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .

Transmission Output Speed Sensor

1. Ignition OFF, disconnect the OSS wiring harness connector X4 (2) from the control solenoid valve assembly.
2. Ignition ON, test for 8.3-9.3 volts at terminal A. If not within the specified range, replace the control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .
3. Ignition OFF, using the EL 35616 terminal test kit, connect the EL 38522 variable signal generator red lead to the OSS signal circuit terminal B on the TCM.
4. Connect the black lead from the EL 38522 variable signal generator to ground.
5. Set the EL 38522 variable signal generator to 5 volts, the frequency to 300 Hz, and the percent duty cycle to 50 or the normal position.
6. Ignition ON, verify with a scan tool the Transmission OSS parameter is between 256-266 RPM. If not within the specified range, replace the control solenoid valve assembly. Refer to «Control Solenoid Valve and Transmission Control Module Assembly Replacement»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-repair-instructions-on-vehicle) .

Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test

Special Tools

1. DT-47825-100 Solenoid Test Plate
2. DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

Scheme 79

The purpose of this procedure is to test the functionality of the control solenoid valve assembly solenoids for a gross stuck open or stuck closed condition. The DT-47825-100 test plate is bolted to the control solenoid valve assembly on the valve body mounting surface. Pressurized air is passed into the aluminum test plate, through the control solenoid valve assembly solenoid passage and back to a pressure gauge on the test plate. The pressure gauge indicates open if air pressure is passed through the solenoid, or closed if the solenoid is unable to pass air through. A scan tool is used to command the solenoids ON and OFF. While watching the pressure gauge, one can determine the valve functionality. The recommended shop air pressure for this test is 90-100 psi.

1. Remove the control solenoid valve assembly from the transmission.
2. Bolt the DT-47825-100 test plate to the control solenoid valve assembly on the valve body mounting surface. Use the bolts and washers supplied with the tool to attach the test plate. Tighten the bolts to 5 N.m (44 lb in) using a center out alternating torque sequence.
3. Install the pressure gauge to the affected solenoid air port. Reference component to air port table.
4. Connect the shop air pressure line to the DT-47825-100 test plate test plate air psi inlet port.
5. Connect the DT-47825-20 harness to the vehicle and control solenoid valve assembly.
6. Ignition ON, with a scan tool command the solenoid in question ON and OFF. Watch the air pressure gauge and look for the change in pressure as you command the valve ON and OFF. The valve should allow air pressure to flow through the valve port to the gauge with a result of pressure reading on the gauge. If the valve is stuck closed, no pressure change will occur. Command the solenoid valve ON and OFF several times to determine the state of the solenoid valve in question. Release the air pressure in the gauge between pressurization tests.

Control Solenoid Valve Assembly Solenoid Performance Test Plate to Component Identification

Note. With the key ON, engine OFF (KOEO), the transmission control module (TCM) will normally cycle some of the transmission solenoids On and Off to facilitate keeping the ports and solenoids clean and free of debris. This dither function is a normal activity and will cause the valves to cycle open and closed quickly when the TCM is powered up. This can cause the psi gauge to flicker high and low as the valves open and close. This may cause some air to exit the ports where the psi gauge is not connected as those solenoids cycle on and off.

Drain the TCM of excess transmission fluid before attaching to test plate and use caution when attaching air to test plate air inlet.

Reset Transmission Adapts

The Reset Transmission Adapts is a procedure for automatic transmissions in which the shift pressure learn values of each individual clutch is reset to zero or a base calibrated value, in the transmission control module (TCM).

Once the transmission adapts are set to zero or a calibrated value, the vehicle is then road test under various drive cycle events for the TCM to relearn shift pressure values for the best possible shift feel in all gear ranges.

The Reset Transmission Adapts procedure must be performed when one of the following repairs have been made to the transmission. Failure to perform the procedure after one of the following repairs may result in poor transmission performance, DTCs being set, or customer dissatisfaction.

1. Transmission internal service, repair or overhaul
2. Valve body repair or replacement
3. Control solenoid valve assembly replacement
4. Any service/repair in response to a shift quality concern

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.
5. Ignition ON, engine running, with a scan tool Reset Transmission Adapts.
6. Perform the «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) .
7. Ignition OFF for 2 minutes.

Brake Pedal Position Sensor Learn

Brake Pedal Position Sensor Learn is a procedure for the ECM to determine the position of the brake pedal position sensor when the brake pedal is in the released position.

1. An Engine Control Module Replacement
2. A BPP Sensor Replacement
3. Any repair procedure that effects the brake pedal position sensor alignment

1. Install a scan tool.
2. Monitor the ECM for DTCs with a scan tool. If other DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/buick/lacrosse/ii-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) for the applicable DTC that set.
3. Navigate to the scan tool Brake Pedal Position Sensor Learn command by selecting the following: Module Diagnosis Engine Control Module Configuration/Reset Functions Learn Functions Brake Pedal Position Sensor Learn
4. Ignition ON, Engine OFF, transmission in Park, brake pedal in the fully released position, select Learn.
5. Verify Brake Pedal Position Sensor and Brake Pedal Position Sensor Learned Home Position are within.1 Volts.
6. Select Exit.
7. Perform the Body Control Module (BCM) brake pedal position sensor calibration. Refer to «Brake Pedal Position Sensor Calibration»(/buick/lacrosse/ii-2009-2013/remont/exterior-lights/#lighting-system-repair-instructions__brake-pedal-position-sensor-calibration) .

Transmission Fluid Level and Condition Check

This procedure checks both the transmission fluid level, as well as the condition of the fluid itself.

Note. Ensure the transmission has enough fluid in it to safely start the vehicle without damaging the transmission. With the vehicle off there must be at least enough fluid to wet the end of the dipstick bullet. This will ensure that there is enough fluid in the sump to fill the components once the vehicle is started.

Level Checking Procedure

1. Park the vehicle on a level surface, apply the parking brake and place the shift lever in PARK (P).
2. Start the engine.
3. Depress the brake pedal and move the shift lever through each gear range, pausing for about 3 seconds in each range. Then move the shift lever back to PARK (P).
4. Allow the engine to idle 500-800 rpm for at least 1 minute. Release the brake pedal.
5. Keep the engine running and observe the transmission fluid temperature (TFT) using the Driver Information Center or a scan tool.
6. If the TFT reading is not within the required temperature ranges, allow the vehicle to cool, or operate the vehicle until the appropriate TFT is reached. Drive the vehicle in second gear until the fluid temperature is within the specified range.
7. Remove the dipstick and wipe it with a clean rag or paper towel.
8. Inspect the fluid color. The fluid should be red or dark brown. If the fluid color is very dark or black and has a burnt odor, inspect the fluid for excessive metal particles or other debris. A small amount of "friction" material is a "normal" condition. If large pieces and/or metal particles are noted in the fluid, flush the oil cooler and cooler lines and overhaul the transmission. If there are no signs of transmission internal damage noted, replace the fluid, repair the oil cooler, and flush the cooler lines. Fluid that is cloudy or milky or appears to be contaminated with water indicates engine coolant or water contamination. Refer to «Engine Coolant/Water in Transmission»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__engine-coolantwater-in-transmission) .
9. Install the dipstick and tighten. Wait three seconds and then remove it again.
10. Check both sides of the dipstick and read the lower level.
11. Install and remove the dipstick again to verify the reading.
12. If the fluid level is not within the crosshatch band, and the transmission temperature is between 180°F and 200°F (82°C and 93°C), add or drain fluid as necessary to bring the level into the crosshatch band. If the fluid level is low, add only enough fluid to bring the level into the crosshatch band. NOTE: Do not add more than one pint (0.5L) at a time without rechecking the level. Once the oil is on the dipstick bullet, it will not take much more fluid to raise the fluid level into the crosshatch band. Do not overfill. Also, if the fluid level is low, inspect the transmission for leaks. Refer to «Fluid Leak Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) .
13. If the fluid level is in the acceptable range, install the dipstick.
14. If the fluid was changed, reset the transmission oil life monitor if applicable.

Fluid Condition Inspection

1. Inspect the fluid color. The fluid should be red in color. The fluid may also turn brown form normal use, and does not always indicate contamination.
2. If the fluid color is very dark or black and has a burnt odor, inspect the fluid for excessive metal particles or other debris which may indicate transmission damage. Refer to «Road Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__road-test) to verify transmission operation. Change the transmission fluid if no other conditions are found.
3. Fluid that is cloudy or milky or appears to be contaminated with water indicates engine coolant or water contamination. Refer to «Engine Coolant/Water in Transmission»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__engine-coolantwater-in-transmission) .

Scheme 80

Special Tools

DT 21867-A Pressure Gauge

For equivalent regional tools, refer to Special Tools .

1. Install a scan tool.
2. Start the engine.
3. Inspect the transmission for the proper fluid level. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
4. Use the scan tool to inspect for any active or stored diagnostic trouble codes.
5. Inspect the manual linkage at the transmission for proper function.
6. Turn the engine OFF.
7. Remove the line pressure test hole plug.
8. Install the DT 21867-A pressure gauge.
9. Access the Scan Tool Transmission Output Controls for the Line PC Solenoid.
10. Start the engine.
11. Use the scan tool to increase and decrease the Line PC Solenoid in increments of approximately 200 KPa (29 psi). The scan tool commands the increment values automatically.
12. Allow the pressure to stabilize between increments.
13. Compare the pressure readings on the DT 21867-A pressure gauge to the actual pressure values in the solenoid valve pressure chart. Refer to «Solenoid Valve Pressure»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__solenoid-valve-pressure) .
14. If the pressure readings vary greatly, refer to «Fluid Pressure High or Low»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__fluid-pressure-high-or-low) .
15. Turn the engine OFF.
16. Remove the DT 21867-A pressure gauge.
17. Install the line pressure test hole plug and tighten to 12 N.m (106 lb in).

Road Test

The following test provides a method of evaluating the condition of the automatic transmission. The test is structured so that most driving conditions would be achieved. The test is divided into the following parts

1. Electrical Function Check
2. Upshift Control and Torque Converter Clutch (TCC) Apply
3. Part Throttle Step-In Downshifts
4. Manual Downshifts
5. Coasting Downshifts
6. Manual Gear Range Selection REVERSE Driver Shift Control

Note. Complete the test in the sequence given. Incomplete testing cannot guarantee an accurate evaluation.

Before the road test, ensure the following

1. The engine is performing properly.
2. Transmission fluid level is correct. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
3. Tire pressure is correct.

During the road test

1. Perform the test only when traffic conditions permit.
2. Operate the vehicle in a controlled, safe manner.
3. Observe all traffic regulations.
4. View the scan tool data while conducting this test. Take along qualified help in order to operate the vehicle safely.
5. Observe any unusual sounds or smells.

After the road test, check the following

1. Inspect for proper transmission fluid level. Refer to «Transmission Fluid Level and Condition Check»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-level-and-condition-check) .
2. Inspect for any diagnostic trouble codes (DTCs) that may have set during the testing. Refer to the applicable DTC.
3. Monitor the scan tool data for any abnormal readings or data.
4. Inspect for fluid leaks. Refer to «Fluid Leak Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) .

Electrical Function Check

Perform this procedure first in order to ensure the electronic transmission components are functioning properly. If these components are not checked, a simple electrical condition could be misdiagnosed.

1. Connect the scan tool.
2. Ensure the gear selector is in PARK and set the parking brake.
3. Start the engine.
4. Verify that the following scan tool data can be obtained and is functioning properly. Refer to «Control Module References»(/buick/lacrosse/ii-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for typical data values. Data that is questionable may indicate a concern. Engine Speed Transmission ISS Transmission OSS Vehicle Speed IMS Commanded Gear Gear Ratio Line PC Sol. Pressure Cmd. Brake Switch ECT, Engine Data List Trans. Fluid Temp. TCM Temperature Calc. Throttle Position Ignition Voltage TFP Switch 1 TFP Switch 3 TFP Switch 4 TFP Switch 5 PC Sol. 2 Pressure Cmd. PC Sol. 3 Pressure Cmd. PC Sol. 4 Pressure Cmd. PC Sol. 5 Pressure Cmd. Shift Solenoid 1 Shift Solenoid 2 TCC PC Sol. Duty Cycle TCC Slip Speed
5. Check the garage shifts. Apply the brake pedal and ensure the parking brake is set. Move the gear selector through the following ranges: PARK to REVERSE REVERSE to NEUTRAL NEUTRAL to DRIVE DRIVE to REVERSE REVERSE to DRIVE Pause 2 to 3 seconds in each gear position. Verify the gear engagements are immediate (less than 2 seconds to complete if trans fluid temperature is above 20°C) and not harsh. Note that these shifts may be almost imperceptible in some applications. Using the scan tool to monitor Transmission ISS achieving 0 RPM can be used to check delay in these cases.
6. Monitor transmission range on the scan tool, transmission data list. Apply the brake pedal and ensure the parking brake is set. Move the gear selector through all ranges. Pause 2 to 3 seconds in each range. Return gear selector to PARK. Verify that all selector positions match the scan tool display.
7. Check throttle position input. Apply the brake pedal and ensure the parking brake is set. Ensure the gear selector is in PARK. Monitor the scan tool Calc. Throttle Position while increasing and decreasing engine speed with the throttle pedal. The scan tool Calc. Throttle Position percentage should increase and decrease with engine speed.

If any of the above checks do not perform properly, record the result for reference after completion of the road test.

Upshift Control and Torque Converter Clutch (TCC) Apply

The TCM calculates the upshift points based primarily on 2 inputs: throttle position and vehicle speed. When the TCM determines that conditions are met for a shift to occur, the TCM commands the shift by varying current to the appropriate PC solenoids to control oncoming and offgoing clutch pressures.

Perform the following steps

1. Monitor the following scan tool parameters: Calc. Throttle Position Vehicle Speed Engine Speed Transmission ISS Transmission OSS Commanded Gear TCC PC Sol. Pressure Cmd. TCC Slip Speed TFP Switch 1 TFP Switch 3 TFP Switch 4 TFP Switch 5 PC Sol. 2 Pressure Cmd. PC Sol. 3 Pressure Cmd. PC Sol. 4 Pressure Cmd. PC Sol. 5 Pressure Cmd. Shift Solenoid 1 and 2
2. Place the gear selector in the DRIVE position.
3. Accelerate the vehicle using a steady throttle position between 15 and 20 percent. Hold the throttle steady.
4. As the transmission upshifts, there should be a noticeable shift feel or engine speed change within 1 to 2 seconds of the commanded gear change. The PC solenoid pressure command should change to "YES" for the oncoming clutch and the PC solenoid pressure command should change to "NO" for the offgoing clutch.
5. Note any harsh, soft or delayed shifts or slipping. Note any noise or vibration.
6. The TCC feel may not be noticeable. In many applications the TCC will apply after the 1-2 shift and TCC events will not be easily detected using engine speed.
7. Monitor TCC PC solenoid pressure command while driving and check TCC slip speed when the pressure command indicates that the TCC is commanded to apply: When the TCC applies, slip speed should be controlled to below 100 RPM when the transmission is not shifting and the throttle is held steady. If the TCC slip exceeds this value for more than 6 seconds after the TCC PC Sol. Pressure Command indicates that the TCC is commanded ON: Check for DTCs. Refer to «Torque Converter Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) .

Part Throttle Step-In Downshifts

1. Place the gear selector in the DRIVE position.
2. Accelerate the vehicle at light throttle (5-15 percent) until 3rd gear is just achieved.
3. Quickly increase throttle angle until commanded gear indicates that a downshift to 2nd gear is commanded.
4. Verify that the transmission downshifts within 2 seconds of the throttle movement.
5. Repeat steps 2 to 4 at higher speed to achieve 4th gear and then step in to command a 4th gear to 3rd gear downshift.
6. Repeat steps 2 to 4 at higher speed to achieve 5th gear and then step in to command a 5th gear to 4th gear downshift.
7. Repeat steps 2 to 4 at higher speed to achieve 6th gear and then step in to command a 6th gear to 5th gear downshift.
8. Note any harsh, soft or delayed shifts or slipping. Note any noise or vibration.

Manual Downshifts

Manual downshift testing is not required since all vehicles equipped are also equipped with some form of Driver Shift Control (DSC). The TCM will automatically override DSC downshifts to protect the transmission from damage.

Coasting Downshifts

1. Place the gear selector in the DRIVE position.
2. Accelerate the vehicle to 6th gear with the TCC applied.
3. Release the throttle and apply the brakes
4. Verify that the downshifts occur as commanded by monitoring gear ratio, which should change after commanded gear changes.

Manual Gear Range Selection

This application does not utilize manual forward gear ranges.

Reverse

Perform the following test using a 10-15 percent throttle position.

1. With the vehicle stopped, move the gear selector to REVERSE.
2. Slowly accelerate the vehicle.
3. Verify that there is no noticeable slip, noise or vibration.

Driver Shift Control (DSC)

Refer to the owner's manual for specific instructions on the type of DSC available in this application. Utilize the DSC to ensure that the transmission responds appropriately to driver's commands. The TCM will upshift automatically when maximum engine speed is achieved and will protect from any downshift which may cause excessive engine RPM.

Torque Converter Stator

The torque converter stator roller clutch can have 2 different malfunctions.

1. The stator assembly freewheels in both directions.
2. The stator assembly remains locked up in both directions.

Poor Acceleration at Low Speed - Stator Roller Clutch Freewheels at All Times

If the stator is freewheeling at all times, the vehicle tends to have poor acceleration from a standstill and at speeds below 48-55 km/h (30-34 mph). At speeds above 48-55 km/h (30-34 mph), the vehicle may act normally.

For poor acceleration at low speeds, you should first determine that the exhaust system is not blocked, and the transmission is in First gear when starting out. If the engine freely accelerates to high RPM in NEUTRAL, you can assume that the engine and the exhaust system are normal. Check for poor performance in DRIVE and REVERSE to help determine if the stator is freewheeling at all times.

Poor Acceleration at High Speed - Stator Roller Clutch is Locked Up at All Times

If the stator is locked up at all times, performance is normal when accelerating from a standstill. Engine RPM and vehicle speed are limited or restricted at speeds above 48-55 km/h (30-34 mph). Visual examination of the converter may reveal a blue color from overheating.

Torque Converter Bearing Noise

Note. Do not confuse this noise with pump whine noise, which is usually noticeable in all gear ranges. Pump whine will vary with line pressure.

Torque converter whine is noticed when the vehicle is stopped and the transmission is in DRIVE or REVERSE. This noise will increase as you increase the engine RPM. The noise will stop when the vehicle is moving or when you apply the torque converter clutch, because there is no slip speed across the bearings.

Perform a stall test to verify that the noise is actually coming from the torque converter

1. Place your foot on the brake.
2. Put the gear selector in DRIVE.
3. Depress the accelerator to approximately 1, 200 RPM for no more than six seconds.

A torque converter noise will increase under this load.

Torque Converter Clutch

The torque converter clutch (TCC) is applied by fluid pressure, which is controlled by a TCC pressure control (PC) solenoid. This solenoid is part of the control solenoid valve assembly, which is located inside the automatic transmission assembly. The solenoid is controlled through a combination of computer controlled switches and sensors. Electronically controlled capacity clutch (ECCC) is controlled slip across the TCC.

Torque Converter Clutch Shudder

The key to diagnosing torque converter clutch (TCC) shudder is to note when it happens and under what conditions. TCC shudder should only occur during the apply, release, or ECCC conditions of the converter clutch. Shudder should never occur after the TCC is fully locked (approximately 0 RPM slip).

If Shudder Occurs During TCC Apply, Release, and ECCC

If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torque converter. Something is causing one of the following conditions to occur

1. The clutch is not engaging completely.
2. The clutch is not releasing completely.
3. The clutch is releasing and applying rapidly and continuously.

One of the following conditions may be causing the TCC Shudder to occur

1. Leaking turbine shaft/TCC seals
2. A restricted release orifice
3. A distorted clutch or converter cover due to long flexplate to converter bolts
4. Defective friction material on the TCC plate

If Shudder Occurs After TCC has Locked

Engine problems may go unnoticed under light throttle and load, but they become noticeable after the TCC has locked when going up a hill or accelerating.

Refer to Symptoms - Engine Controls in order to avoid misdiagnosis of TCC shudder and the unnecessary disassembly of a transmission or the unnecessary replacement of a torque converter.

Torque Converter Vibration Test

Note. The Noise and Vibration Analysis procedure should be performed prior to performing this test.

Indexing Torque Converter

To determine and correct a torque converter vibration, the following procedure may have to be performed several times to achieve the best possible torque converter to flexplate balance.

1. Remove the torque converter bolts.
2. Rotate the torque converter one bolt position from the original marked position.
3. Align the torque converter pilot (2) in the engine crankshaft (3). Install the torque converter to flexplate bolts, and tighten according to «Fastener Tightening Specifications (On Vehicle)»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__fastener-tightening-specifications-on-vehicle) , «Fastener Tightening Specifications (Off Vehicle)»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__fastener-tightening-specifications-off-vehicle) .
4. Lower the vehicle.
5. With the engine at idle speed and the transmission in PARK or NEUTRAL, observe the vibration. Repeat this procedure until the best possible balance is obtained.
6. Install the torque converter access cover and bolts (if equipped) and tighten according to «Fastener Tightening Specifications (On Vehicle)»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__fastener-tightening-specifications-on-vehicle) , «Fastener Tightening Specifications (Off Vehicle)»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-specifications__fastener-tightening-specifications-off-vehicle) .

Torque Converter Replacement Guide

Composition Plates

Dry the plates and inspect the plates for the following conditions

1. Pitting
2. Flaking
3. Delamination-splitting or separation of bonded clutch material
4. Wear
5. Glazing
6. Cracking
7. Charring
8. Chips or metal particles embedded in the lining

Replace a composition plate which shows any of these conditions.

Steel Plates

Wipe the plates dry and check the plates for heat discoloration. If the surfaces are smooth, even if color smear is indicated, you can reuse the plate. If the plate is discolored with heat spots or if the surface is scuffed, replace the plate.

Causes of Burned Clutch Plates

The following conditions can result in a burned clutch plate

1. Incorrect usage of clutch or apply plates
2. Engine coolant or water in the transmission fluid
3. A cracked clutch piston
4. Damaged or missing seals
5. Low line pressure
6. Valve body conditions The valve body face is not flat. Porosity in between channels. The valve train retainers are improperly installed. The checkballs are misplaced.
7. The Teflon® seal rings are worn or damaged.

Engine Coolant/Water in Transmission

If antifreeze or water has entered the transmission, perform the following

1. Disassemble the transmission.
2. Replace all of the rubber type seals. The coolant will attack the seal material which will cause leakage.
3. Replace the composition-faced clutch plate assemblies. The facing material may separate from the steel center portion.
4. Replace all of the nylon parts - washers.
5. Replace the torque converter.
6. Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.
7. Flush the cooler lines after the transmission cooler has been properly repaired or replaced.
8. Inspect the rubber hose portion of the oil cooler lines for damage, if applicable. Refer to «Transmission Fluid Cooler Flushing and Flow Test»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures__transmission-fluid-cooler-flushing-and-flow) .

General Method

1. Verify that the leak is transmission fluid.
2. Thoroughly clean the suspected leak area using a rag.
3. Operate the vehicle for 15-20 minutes under city driving conditions until normal operating temperatures are reached.
4. Park the vehicle over clean paper or cardboard.
5. Shut OFF the engine.
6. Look for fluid spots on the paper.
7. Make the necessary repairs.

Powder Method

1. Thoroughly clean the suspected leak area using a rag.
2. Apply an aerosol type leak tracing powder to the suspected leak area.
3. Operate the vehicle for 15-20 minutes under city driving conditions until normal operating temperatures are reached.
4. Shut OFF the engine.
5. Inspect the suspected leak area.
6. Trace the leak path through the powder in order to find the source of the leak.
7. Make the necessary repairs.

Dye and Black Light Method

A fluid dye and black light kit is available from various tool manufacturers.

1. Follow the manufacturer's instructions in order to determine the amount of dye to use.
2. Operate the vehicle for 24 km (15 mi) or until normal operating temperatures are reached.
3. Detect the leak with the black light.
4. Make the necessary repairs.

Find the Cause of the Leak

Pinpoint the leak and trace the leak back to the source. You must determine the cause of the leak in order to repair the leak properly. For example, if you replace a gasket, but the sealing flange is bent, the new gasket will not repair the leak. You must also repair the bent flange. Before you attempt to repair a leak, check for the following conditions, and make repairs as necessary

Gaskets

1. Fluid level/pressure is too high
2. Plugged vent or drain-back holes
3. Improperly tightened fasteners
4. Dirty or damaged threads
5. Warped flanges or sealing surface
6. Scratches, burrs, or other damage to the sealing surface
7. Damaged or worn gasket
8. Cracking or porosity of the component
9. Improper sealant used, where applicable
10. Incorrect gasket

Seals

1. Fluid level/pressure is too high
2. Plugged vent or drain-back holes
3. Damaged seal bore
4. Damaged or worn seal
5. Improper installation
6. Cracks in component
7. Manual shaft or output shaft surface is scratched, nicked, or damaged
8. Loose or worn bearing causing excess seal wear

Possible Points of Fluid Leaks

Transmission Case Cover and/or Valve Body Cover

1. Incorrectly tightened bolts
2. Improperly installed or damaged gasket/seal
3. Damaged mounting face
4. Incorrect gasket seal

Case Leak

1. Damaged input speed sensor seal
2. Damaged manual shaft seal
3. Loose or damaged oil cooler lines/seals
4. Worn or damaged axle shaft oil seal
5. Loose line pressure pipe plug or fluid level pipe plug
6. Porous casting
7. Warped torque converter housing
8. Damaged converter housing to case seal

Leak at the Torque Converter End

1. Converter leak in the weld area
2. Converter seal lip cut. Check the converter hub for damage
3. Converter seal bushing moved forward and damaged
4. Converter seal garter spring missing from the seal
5. Porous casting of the torque converter housing

Leak at the Vent

1. Overfilled system
2. Water or coolant in the fluid; The fluid will appear milky
3. Transmission case porous
4. Incorrect fluid level indicator causing an overfilled system
5. Plugged vent

Scheme 81

Case Porosity Repair

Some external leaks are caused by case porosity in non-pressurized areas.

1. Thoroughly clean the area to be repaired with a cleaning solvent. Air dry the area.
2. Using instructions from the manufacturer, mix a sufficient amount of an epoxy to make the repair.
3. Apply the epoxy. A clean, dry soldering acid brush can be used to clean the area and also to apply the epoxy cement. Make certain that the area to be repaired is fully covered.
4. Allow the epoxy cement to cure for three hours before assembling the components.
5. Repeat the fluid leak diagnosis procedures.

Transmission Fluid Cooler Flushing and Flow Test

GM studies indicate that plugged or restricted transmission oil coolers and pipes cause insufficient transmission lubrication and elevated operating temperatures which can lead to premature transmission failure. Many repeat repair cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flow checking and flushing the auxiliary transmission oil cooler, if equipped.

Note. Use the DT 45096 transmission oil cooling system flush and flow test tool or equivalent to flush and flow test the transmission oil cooler and the oil cooler pipes after the transaxle is removed for repairs.

Only GM Goodwrench DEXRON®VI automatic transmission fluid should be used when doing a repair on a GM transmission.

Time allowance for performing the cooler flow checking and flushing procedure has been included in the appropriate labor time guide operations since the 1987 model year. The service procedure steps for oil cooler flushing and flow testing are as follows

Cooler Flow Check and Flushing Steps

1. Machine Set-up
2. Determine Minimum Flow Rate
3. Back Flush
4. Forward Flush
5. Flow Test
6. Code Recording Procedure
7. Clean-up

Special Tools

1. DT 45096 Transmission Oil Cooling System Flush and Flow Test Tool
2. DT 45096-50 Transmission Cooler Flush Adapter
3. Shop air supply with water/oil filters, regulator and pressure gauge - minimum 90 psi
4. Eye protection
5. Rubber gloves

For equivalent regional tools, refer to Special Tools .

Machine Set-up

1. Verify that the main power switch (1) is in the OFF position.
2. Place the main function switch (2) in the IDLE position.
3. Connect DT 45096 flush and flow test tool to the vehicle 12V DC power source by connecting the red battery clip to the positive, +, battery post on the vehicle and connect the negative lead to a known good chassis ground.
4. Turn the main power switch to the ON position.
5. Fill the supply tank with Dexron®VI through the fill port.
6. Reinstall and tighten the fill cap.
7. Connect a shop air supply hose to the quick-disconnect on the rear panel marked SUPPLY AIR.

Determine Minimum Flow Rate

1. From the machine display, identify the temperature of the automatic transmission fluid that is stored in the supply vessel of DT 45096 flush and flow test tool.
2. Determine whether the transmission oil cooler is steel or aluminum by using a magnet (1) at the cooler flange (2) at the radiator.
3. Refer to the table below. Using the temperature from step 1, locate on either the Steel MINIMUM Flow Rate table or the Aluminum MINIMUM Flow Rate table the minimum flow rate in gallons per minutes (GPM). Record the minimum flow rate in GPMs and the supply fluid temperature for further reference. Example Fluid temperature: 75°F Cooler type: Steel The MINIMUM flow rate for this example would be 0.8 GPM.
4. Inspect transmission oil cooler lines for damage or kinks that could cause restricted oil flow. Repair as needed and refer to the appropriate GM service manual procedures.

Minimum Flow Rate in Gallons Per Minute (gpm)

Back Flush Procedure

1. Connect the DT 45096-50 cooler flush adapter (1) to the vehicle transmission oil cooler supply and return lines at the transmission.
2. Connect the black supply hose (1) to the return line, top connector of the transmission, and the clear waste hose (2) to the feed line, bottom connector of the transmission, to the vehicle cooler lines. This is the reverse flow - backflush direction.
3. Turn the main function switch to the FLUSH position. Allow the machine to operate for 30 seconds.
4. Turn the main function switch to the IDLE position and allow the supply vessel pressure to dissipate.

Forward Flush

1. Disconnect the supply and waste hoses from the vehicle cooler lines. Reverse the supply and waste hoses to provide a normal flow direction.
2. Turn the main function switch to the FLUSH position and allow machine to operate for 30 seconds.

Flow Test

1. Turn the main function switch to the FLOW position and allow the oil to flow for 15 seconds. Observe and note the flow rate; this is the TESTED flow rate.
2. Compare the TESTED flow rate to the MINIMUM flow rate information previously recorded. If the TESTED flow rate is equal to or greater than the MINIMUM flow rate recorded, the oil cooling system is functioning properly. Perform Code Recording Procedure. If the TESTED flow rate is less than the MINIMUM flow rate previously recorded, repeat the back flush and forward flush procedures.
3. If the TESTED flow rate is less than the MINIMUM flow rate after the second test, perform Code Recording Procedure. Replace the transmission oil cooler. Reconnect supply and waste hoses to the cooler lines in the normal flow direction. Perform Flow Test. Perform Code Recording Procedure.

Code Recording Procedure

1. Turn the main function switch to the CODE position.
2. Record TESTED flow rate, temperature, cycle and seven-character flow code information on repair order.

Clean-up

1. Turn the main function switch (2) to the IDLE position and allow the supply vessel pressure to dissipate.
2. Turn the main power switch (1) to the OFF position.
3. Disconnect the supply and waste hoses and the 12-volt power source from the vehicle.
4. Disconnect the air supply hose from DT 45096 flush and flow test tool.
5. Dispose of the waste ATF in accordance with all applicable federal, state, and local requirements.

Bushing and Mating Shaft Inspection

Note. Proper bushing and corresponding mating shaft inspection should be performed before replacing the bushing, shaft, and in some cases, the component which houses the bushing. Thoroughly clean and dry the bushing and shaft surfaces before inspecting for damage.

Any of the following bushing conditions require replacement of the bushing and/or housing

1. Discoloration due to heat distress
2. Misalignment or displacement of bushing as a result of spinning in housing
3. Medium to heavy scoring that can be easily detected with fingernail. Light scoring is a normal condition.
4. Debris embedded into the bushing lining material
5. Obvious damage, including excessive and uneven wear
6. Excessive polishing. Minor polishing of the bushing is an indication of normal wear and does not require replacement.

Any of the following conditions require replacement of the bushing's mating shaft

1. Discoloration due to heat distress
2. Rough surface finish that can be easily detected with finger
3. Obvious shaft abnormalities, including warping or uneven surfaces
4. Obvious damage or cracking

Noise and Vibration Analysis

A noise or vibration that is noticeable when the vehicle is in motion MAY NOT be the result of the transmission.

If noise or vibration is noticeable in PARK and NEUTRAL with the engine at idle, but is less noticeable as RPM increases, the vibration may be a result of poor engine performance.

1. Vibration may also be caused by a small amount of water inside the converter.
2. Inspect the engine and transmission mounts for damage and loose bolts.
3. Inspect the transmission case mounting holes for the following conditions: Missing bolts, nuts, and studs Stripped threads Cracks
4. Inspect the flywheel for the following conditions: Missing or loose bolts Cracks Imbalance
5. Inspect the torque converter for the following conditions: Missing or loose bolts or lugs Missing or loose balance weights Imbalance caused by heat distortion or fluid contamination
6. If the noise or vibration is noticeable in PARK and NEUTRAL with the engine at idle, but is more noticeable as RPM increases, the vibration may be an engine imbalance or a transmission imbalance. Refer to «Torque Converter Diagnosis»(/buick/lacrosse/ii-2009-2013/remont/automatic-trans/#automatic-transmission-6t70-diagnostic-information-and-procedures) .

Whine/Growl Noise

Whine/Growl Noise

Automatic Transmission Fluid Leaks

Automatic Transmission Fluid Leaks

Shift Indicator Indicates Wrong Gear Selection

Shift Indicator Indicates Wrong Gear Selection

No Park

No Park

Harsh Garage Shift

Harsh Garage Shift

No Drive in All Ranges

No Drive in All Ranges

No First and Reverse Gears

No First and Reverse Gears

No First, Second, Third, and Fourth Gear

No First, Second, Third, and Fourth Gear

No Second and Sixth Gear

No Second and Sixth Gear

Harsh or Late First, Second, Third, and Fourth Shift

Harsh or Late First, Second, Third, and Fourth Shift

Harsh First and Reverse Shift

Harsh First and Reverse Shift

No Third, Fifth, and Reverse Gear

No Third, Fifth, and Reverse Gear

Harsh or Late Second and Sixth Shift

Harsh or Late Second and Sixth Shift

No Fourth, Fifth, and Sixth Gear

No Fourth, Fifth, and Sixth Gear

Harsh or Late Third, Fifth, and Reverse Shift

Harsh or Late Third, Fifth, and Reverse Shift

Harsh Fourth, Fifth, and Sixth Shift

Harsh Fourth, Fifth, and Sixth Shift

No Torque Converter Clutch Apply

No Torque Converter Clutch Apply

No Torque Converter Clutch Release

No Torque Converter Clutch Release

Harsh Torque Converter Clutch Apply, or Inoperative or No Electronically Controlled Capacity Clutch Control

Harsh Torque Converter Clutch Apply, or Inoperative or No Electronically Controlled Capacity Clutch Control

No Reverse Gear

No Reverse Gear

Fluid Pressure High or Low

Fluid Pressure High or Low

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Automatic Transmission Controls Schematics
• COMPONENT CONNECTOR END VIEWS - INDEX
• Inline Harness Connector End Views
• Transmission General Description
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Special Tools
• Charging System Test
• Diagnostic Repair Verification
• Engine Controls Schematics (LFX)
• Exterior Lights Schematics
• Diagnostic Trouble Code (DTC) List - Vehicle
• Brake Pedal Position Sensor Replacement
• Electronic Component Description
• Control Solenoid Valve and Transmission Control Module Assembly Programming and Setup (6T30/6T40/6T45/6T50)
• Control Solenoid Valve and Transmission Control Module Assembly Replacement
• Transmission Component and System Description
• Engine Overheating
• Transmission Fluid Cooler Flushing and Flow Test
• Transmission General Description
• Transmission Component and System Description
• Solenoid Valve Pressure
• Torque Converter Removal
• Drive Range, First Gear
• Drive Range, Third Gear
• Drive Range, First Gear Engine Braking
• Parking Brake and Drive Wheels Warning
• Transmission Fluid Pressure Switch Logic
• Range Selector Lever Cable Adjustment
• Transmission Internal Mode Switch Logic
• Range Selector Lever Cable Adjustment
• Data Link Communications Description and Operation
• Scan Tool Does Not Communicate with High Speed GMLAN Device
• Diagnostic Starting Point - Vehicle
• Brake Pedal Position Sensor Calibration
• Fastener Caution
• Symptoms - Engine Controls
• Fastener Tightening Specifications (On Vehicle)
• Fastener Tightening Specifications (Off Vehicle)
• Symptoms - Engine Mechanical
• Lower Engine Noise, Regardless of Engine Speed
• Reset Transmission Adapts
• Control Solenoid Valve and Transmission Control Module Assembly Inspection
• Brake Pedal Position Sensor Learn
• Transmission Fluid Level and Condition Check
• Control Solenoid Valve and Transmission Control Module Assembly Input Shaft Speed/Output Shaft Speed Input Test
• Road Test
• Fluid Pressure High or Low
• Automatic Transmission Fluid Leaks
• Whine/Growl Noise
• Noise and Vibration Analysis
• No Park
• No Drive in All Ranges
• No Reverse Gear
• Harsh Garage Shift
• Harsh or Late First, Second, Third, and Fourth Shift
• Harsh First and Reverse Shift
• Harsh or Late Second and Sixth Shift
• Harsh or Late Third, Fifth, and Reverse Shift
• Harsh Fourth, Fifth, and Sixth Shift
• No First and Reverse Gears
• No First, Second, Third, and Fourth Gear
• No Second and Sixth Gear
• No Fourth, Fifth, and Sixth Gear
• No Third, Fifth, and Reverse Gear
• No Torque Converter Clutch Apply
• No Torque Converter Clutch Release
• Engine Coolant/Water in Transmission
• Symptoms - Automatic Transmission
• Transmission Fluid Cooler Flushing and Flow Test