Automatic Transaxle Diagnosis - 4t65-e Buick Century VI

APPLICATION

TRANSAXLE APPLICATION

IDENTIFICATION

Transaxle has a metal identification plate or Service Replacement Transmission Assembly (SRTA) plate attached to rear face of transaxle. (Scheme 261) Transaxle RPO codes are MN7 or M15. Century models use RPO code M15. Regal models use RPO code MN7 or M15. The MN7 is a heavy duty model and has a 10.2" (258 mm) torque converter. The M15 model has a 9.6" (245 mm) torque converter.

Scheme 261

SHIFT SOLENOID VALVE OPERATION & GEAR RATIOS

SHIFT SOLENOID VALVE OPERATION & GEAR RATIOS

DESCRIPTION & OPERATION

Note. For additional information on transaxle operation, see DESCRIPTION & OPERATION in 4T65-E OVERHAUL article.

INTRODUCTION

The 4T65-E is a fully automatic front wheel drive electronically controlled transaxle. The 4T65-E provides four forward ranges including O/D. The Powertrain Control Module (PCM) controls shift points by means of two shift solenoids. A vane-type oil pump supplies the oil pressure. The PCM regulates oil pressure by means of a pressure control solenoid valve.

All vehicles equipped with a 4T65-E transaxle have an Electronically Controlled Capacity Clutch (ECCC) system. In the ECCC system, the pressure plate does not fully lock to the torque converter cover. Instead, it is precisely controlled to maintain a small amount of slippage between the engine and the turbine, reducing driveline torsional disturbances.

You can operate the transaxle in any one of the following seven modes

1. P Park position prevents the vehicle from rolling either forward or backward. For safety reasons, use the parking brake in addition to the Park position.
2. R Reverse allows the vehicle to be operated in a rearward direction.
3. N Neutral allows the engine to be started and operated while driving the vehicle. If necessary, you may select this position to restart the engine with the vehicle moving.
4. D O/D is used for all normal driving conditions. O/D provides four gear ratios plus a converter clutch operation. Depress the accelerator to downshift for safe passing.
5. 3 Drive position is used for city traffic and hilly terrain. Drive provides three gear ranges and drive range prevents the transaxle from operating in 4th gear. Depress the accelerator to downshift.
6. 2 Manual 2nd provides two gear ratios under most operating conditions. Manual 2nd provides acceleration and engine braking. Select this range at any vehicle speed, but the transaxle will not downshift into 2nd gear until the vehicle speed drops below approximately 62 MPH.
7. 1 Manual Low provides maximum engine braking. You may also select this range at any vehicle speed, but the transaxle will not downshift into 1st gear until the vehicle speed drops below approximately 37 MPH.

ADAPT FUNCTION

The 4T65-E transaxle uses a line pressure control system that has the ability to adapt line pressure to compensate for normal wear of the following parts

1. The clutch fiber plates.
2. The springs and seals.
3. The apply bands.

The PCM maintains information for the following transaxle adaptive systems

Upshift Adapts (1-2, 2-3 & 3-4)

The PCM monitors the Input Shaft Speed (ISS) sensor and the Vehicle Speed Sensor (VSS) to determine when an upshift has started and completed. The PCM measures the time for the upshift. If the upshift time is longer than a calibrated value, then the PCM will adjust the current to the Pressure Control (PC) solenoid valve to increase the line pressure for the next shift in the same torque range. If the upshift time is shorter than the calibrated value, then the PCM will decrease the line pressure for the next shift in the same torque range.

Steady State Adapts

The PCM monitors the ISS sensor and the VSS after an upshift to determine the amount of clutch slippage. If excessive slippage is detected, then the PCM will adjust the current to the PC solenoid valve. This will increase the line pressure to maintain the proper gear ratio for the commanded gear.

The Transmission Adaptive Pressure (TAP) information is divided into 13 units called cells. The cells are numbered 4 through 16. Each cell represents a given torque range. TAP cell 4 is the lowest adaptable torque range, and TAP cell 16 is the highest adaptable torque range. It is normal for TAP cell values to display zero or negative numbers. This indicates that the PCM has adjusted line pressure at or below the calibrated base pressure.

Clearing Transmission Adaptive Pressure (TAP)

Updating TAP information is a learning function of the PCM designed to maintain acceptable shift times. It is not recommended that TAP information be reset unless one of the following repairs has been made

1. Transaxle overhaul or replacement.
2. Repair or replacement of an apply or release component (clutch, band, piston, servo).
3. Repair or replacement of a component or assembly which directly affects line pressure.

Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, the PCM will need to relearn TAP values. Transaxle performance may be affected as new TAPs are learned. The PCM must also relearn TAP values when the PCM or the transaxle is replaced.

TRANSAXLE COMPONENTS & SYSTEMS

Note. For transaxle electronic component locations (Scheme 262)

The mechanical components of this unit are as follows

1. A torque converter with an Electronically Controlled Capacity Clutch (ECCC).
2. A drive link assembly.
3. Four multiple disk clutch assemblies: Input, 2nd, 3rd and 4th.
4. Three friction bands: Forward band, 2-1 band and Reverse band.
5. Two planetary gear sets: Input and Reaction.
6. Three one-way clutches: one roller clutch (1-2 support) and two sprag clutches (3rd and Input).
7. A final drive and differential assembly.
8. One control valve assembly.
9. One vane type oil pump.

The electrical components of this unit are as follows

1. Two shift solenoid valves: 1-2 and 2-3.
2. A Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve.
3. A Pressure Control (PC) solenoid valve.
4. A Transmission Fluid Temperature (TFT) sensor.
5. Two speed sensors: input shaft and vehicle speed sensors.
6. A Transmission Fluid Pressure (TFP) manual valve position switch.
7. A transaxle range switch.
8. A transaxle internal wiring harness assembly.

Scheme 262

ELECTRONIC COMPONENTS

Note. For transaxle electronic component locations (Scheme 262)

Vehicle Speed Sensor

The Vehicle Speed Sensor (VSS) is a magnetic inductive pickup that relays vehicle speed information to the PCM. (Scheme 262)and (Scheme 263). The PCM uses this information to control shift timing, line pressure, and TCC apply and release.

The VSS mounts in the case extension at the VSS reluctor wheel, which is pressed onto the final drive carrier assembly. An air gap of .011-.062" (.27-1.57 mm) occurs between the sensor and the teeth on the VSS reluctor wheel as the final drive carrier assembly rotates.

The sensor consists of a permanent magnet surrounded by a coil of wire. As the VSS reluctor wheel on the final drive carrier assembly rotates, an AC signal is produced by the VSS. This AC signal consists of a voltage and frequency that changes based on vehicle speed. The PCM uses the frequency portion of this signal to determine vehicle speed. Higher vehicle speeds induce a higher frequency and a higher voltage measurement at the sensor. The voltage portion of the signal is used in diagnostic procedures.

Sensor resistance should measure between 1650-2200 ohms at 68°F (20°C). Output voltage will vary with vehicle speed from a minimum of .5 volts AC at 100 RPM to 200 volts at 6000 RPM.

Scheme 263

Input Shaft Speed Sensor

The Input Shaft Speed (ISS) sensor is a magnetic inductive pickup that relays turbine shaft speed information to the PCM. (Scheme 262)and (Scheme 264). The PCM uses ISS sensor information to control line pressure, transaxle shift patterns, and TCC apply and release. This information is also used to calculate the appropriate operating gear ratios and TCC slippage.

The ISS sensor mounts in the case cover, next to the ISS sensor reluctor wheel assembly. An air gap of .0032-.0834" (.08-2.12 mm) occurs between the sensor and the teeth on the speed sensor reluctor wheel as the drive sprocket rotates. The speed sensor reluctor wheel is secured to and turns with the drive sprocket by the tangs on the drive sprocket forward thrust washer.

The sensor consists of a permanent magnet surrounded by a coil of wire. As the turbine shaft rotates the speed sensor reluctor wheel and the drive sprocket, an AC signal is produced by the ISS sensor. This AC signal consists of a voltage and frequency that changes based on vehicle speed. The PCM uses the frequency portion of this signal to determine input shaft speed. Higher input shaft speeds induce a higher frequency and a higher voltage measurement at the sensor. The voltage portion of the signal is used in diagnostic procedures.

Sensor resistance should measure between 820-1020 ohms at 68°F (20°C). Output voltage will vary with the vehicle speed from a minimum of .5 volts AC at 300 RPM to 200 volts at 6000 RPM.

Scheme 264

1-2 & 2-3 Shift Solenoid Valves

The shift solenoid valves are two identical, normally open, electronic exhaust valves that control upshifts and downshifts in all forward gear ranges. (Scheme 262)and (Scheme 265). These shift solenoid valves work together in a combination of ON and OFF sequences to control the positions of the 1-2 and 2-3 shift valve trains. The PCM monitors numerous inputs to determine the appropriate solenoid state combination and the transaxle gear for the vehicle operating conditions. See SHIFT SOLENOID VALVE OPERATION & GEAR RATIOS.

The PCM energizes the shift solenoids by providing a ground to the solenoid's electrical circuit. This sends a current through the coil winding of the solenoid, thereby creating a magnetic field. The magnetic field repels the plunger inside the solenoid. This seats the solenoid metering ball against the fluid inlet port. This action prevents the exhaust of fluid through the solenoid and provides an increase in fluid pressure at the end of the shift valves. This fluid pressure initiates an upshift by moving the shift valves.

Shift solenoid resistance should measure between 19-24 ohms when measured at 68°F (20°C) and between 24-31 ohms when measured at 190°F (88°C).

The shift solenoid valves should energize when the voltage is greater than 7.5 volts. The shift solenoid valves should de-energize when the voltage is less than one volt.

Scheme 265

Pressure Control Solenoid Valve

The Pressure Control (PC) solenoid valve is a precision electronic pressure regulator that controls transmission line pressure based on current flow through its coil windings. (Scheme 262)and (Scheme 266). As current flow is increased, the magnetic field which is produced by the coil moves the solenoid's plunger further away from the exhaust port. Opening the exhaust port decreases the output fluid pressure, which is regulated by the PC solenoid valve. This ultimately decreases line pressure. The PCM controls the PC solenoid valve based upon various inputs including throttle position, fluid temperature, MAP sensor, and gear operation.

The PCM controls the PC solenoid valve on a positive duty cycle at a fixed frequency of 585 Hz (cycles per second). Duty cycle is defined as the percentage of time when current flows through the solenoid coil during each cycle. A higher duty cycle provides a greater current flow through the solenoid. The high (positive) side of the PC solenoid valve electrical circuit at the PCM controls the PC solenoid valve operation. The PCM provides a ground path for the circuit, monitors average current, and continuously varies the PC solenoid valve duty cycle to maintain the correct average current flowing through the PC solenoid valve. See PC SOLENOID VALVE DUTY CYCLE table.

The PC solenoid valve resistance should measure between 3-5 ohms when measured at 68°F (20°C).

PC SOLENOID VALVE DUTY CYCLE

Scheme 266

Torque Converter Clutch Pulse Width Modulation Solenoid Valve

The Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve is a normally closed (hydraulically). Pulse width modulation solenoid is used to control the apply and release of the converter clutch. (Scheme 262)and (Scheme 267). The PCM operates the solenoid with a negative duty cycle at a fixed frequency of 32 Hz to control the rate of TCC apply/release. The solenoid's ability to ramp the TCC apply and release pressures results in smoother TCC operation.

When the vehicle's operating conditions are appropriate to apply the TCC, the PCM immediately increases the duty cycle to approximately 22 percent. The PCM then ramps the duty cycle up to a maximum of 98 percent to achieve full TCC apply pressure. The rate at which the PCM increases the duty cycle controls the TCC apply. Similarly, the PCM also ramps down the TCC solenoid duty cycle to control TCC release.

Some operating conditions prevent or enable TCC apply under various conditions. See TRANSMISSION FLUID TEMPERATURE SENSOR . Also, if the PCM receives a zero voltage signal from the TCC brake switch, signaling that the brake pedal has been depressed, the PCM immediately releases the TCC.

TCC duty cycle for ECCC equipped vehicles is 22 percent for minimum apply pressure and 43 percent for maximum apply pressure. The TCC PWM solenoid valve will typically be 40-60 percent at full apply. Actual results may vary.

The TCC PWM solenoid valve resistance should measure 10-12 ohms when measured at 68°F (20°C), and 13-15 ohms when measured at 190°F (88°C).

Scheme 267

Transmission Fluid Pressure Manual Valve Position Switch

The Transmission Fluid Pressure (TFP) manual valve position switch is attached to the valve body and consists of one fluid pressure switch that monitors TCC release pressure. (Scheme 262)and (Scheme 268). This switch is used as a diagnostic tool to confirm that the TCC is actually OFF when it has been commanded OFF by the PCM.

The TCC release switch is a normally-closed pressure switch. A normally-closed switch allows current to flow from the positive contact through the switch to ground when no fluid is present. Fluid pressure moves the diaphragm to disconnect the positive and ground contacts, opening the switch and stopping current flow. This change in switch status electronically signals the PCM that the TCC is released.

Scheme 268

Lever Assembly/Manual Shaft Detent With Internal Mode Switch

The lever assembly/manual shaft detent with Internal Mode Switch (IMS) is a sliding contact electrical switch assembly that corresponds to the PRNDL position selected. (Scheme 262)and (Scheme 269). Each of the PRNDL positions has a unique ground pattern on four wires from the PCM.

The assembly consists of two major components

1. The internal mode switch that consists of the housing, which makes up the stationary contacts, and the insulator, which makes up the moving contacts and is secured on the detent lever.
2. The lever assembly which consists of the manual shaft and the detent lever.

The range detection is accomplished by securing the moving contacts to the detent lever. When the driver selects a PRNDL position, the detent lever inside the transmission rotates. This rotates the insulator which in turn grounds the four wires in a unique pattern for each gear selection, corresponding to the PRNDL position selected. The IMS is electrically connected by five wires (four of which the PCM supplies voltage to and one wire that is a common ground) to the transmission that pass through connector.

Scheme 269

Transmission Fluid Temperature Sensor

The Transmission Fluid Temperature (TFT) sensor is a negative temperature coefficient thermistor (temperature sensitive resistor) that provides information to the PCM regarding the transmission fluid temperature. (Scheme 262)and (Scheme 270). The TFT sensor clips on to the valve body, and is replaced as a separate component and not as a part of the transaxle internal wiring harness assembly. The TFT sensor monitors non-pressurized fluid in the sump to determine the operating temperature of the transmission fluid.

The internal electrical resistance of the sensor varies in relation to the operating temperature of the transmission fluid. The PCM sends a 5-volt reference signal to the TFT sensor, and the PCM measures the voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the TFT sensor, which produces a higher voltage signal.

The PCM uses this input to help determine the proper line pressure, shift schedules and TCC apply. When the transmission fluid temperature reaches 266°F (130°C), the PCM enters hot mode. Above this temperature the PCM modifies the transaxle shift schedules and the TCC apply in an attempt to reduce the fluid temperature by reducing the transaxle heat generation. During hot mode, the PCM applies the TCC at all times in 3rd and 4th gears. Also, the PCM performs the 2-3 and the 3-4 shifts earlier to help reduce fluid heat generation.

The PCM stays in hot mode until the temperature drops below 248°F (120°C).

Scheme 270

INLINE 20-PIN CONNECTOR

The transmission electrical connector is an important part of the transmission operating system. (Scheme 271) Any interference with the electrical connection can cause the transmission to set Diagnostic Trouble Codes (DTCs) or affect proper operation.

The following items can affect the electrical connection

1. Bent pins in the connector from rough handling during connection or disconnection.
2. Wires that are within either the internal or external wiring harness which back away from the pins or become uncrimped.
3. Dirt contamination entering the connector when disconnected.
4. Pins in the internal wiring connector backing out of the connector or pushed out of the connector during reconnection.
5. Excessive transmission fluid leaking into the connector, wicking up into the external wiring harness and degrading the wire insulation.
6. Moisture intrusion in the connector.
7. Low pin retention in the external connector from excessive connection and disconnection of the wiring connector assembly.
8. Pin corrosion from contamination.
9. Damaged connector assembly.

Remember the following points

1. In order to remove the connector, squeeze the two tabs toward each other and pull straight up without pulling by the wires.
2. Limit twisting or wiggling the connector during removal. Bent pins can occur.
3. DO NOT pry the connector off with a screwdriver or other tool.
4. Visually inspect the seals to ensure that they are not damaged during handling.
5. In order to reinstall the external wiring connector, first orient the pins by lining up the arrows on each half of the connector. Push the connector straight down into the transmission without twisting or angling the mating parts.
6. The connector should click into place with a positive feel and/or noise.
7. Whenever the transmission external wiring connector is disconnected from the internal harness and the engine is operating, DTCs will set. Clear these DTCs after reconnecting the external connector.

Scheme 271

Description

The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The Powertrain Control Module (PCM) is the control center of this system. The PCM monitors numerous engine and vehicle functions. The PCM constantly looks at the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The PCM also performs the diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the Malfunction Indicator Lamp (MIL). When the PCM detects a malfunction, the PCM stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a buffered voltage to various sensors and switches. Review the components and wiring diagrams in order to determine which systems are controlled by the PCM.

The following are some of the functions that the PCM controls

1. The engine fueling.
2. The Ignition Control (IC).
3. The Knock Sensor (KS) system.
4. The Evaporative Emissions (EVAP) system.
5. The Secondary Air Injection (AIR) system (if equipped).
6. The Exhaust Gas Recirculation (EGR) system.
7. The automatic transmission functions.
8. The generator.
9. The A/C clutch control.
10. The cooling fan control.

Operation

The PCM constantly looks at the information from various sensors and other inputs and controls systems that affect vehicle performance and emissions. The PCM also performs diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the Malfunction Indicator Lamp (MIL). When the PCM detects a malfunction, the PCM stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a buffered voltage to various sensors and switches. The input and output devices in the PCM include analog-to-digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches that complete a ground or voltage circuit when turned on. Most PCM controlled components are operated via output drivers. The PCM monitors these driver circuits for proper operation and, in most cases, can set a DTC corresponding to the controlled device if a problem is detected.

Malfunction Indicator Lamp (MIL)

The Malfunction Indicator Lamp (MIL) is located in the instrument panel cluster. The MIL will display as either SERVICE ENGINE SOON or the check engine light. The MIL indicates that an emissions related fault has occurred and vehicle service is required.

The following is a list of the modes of operation for the MIL

1. The MIL illuminates when the ignition is turned ON, with the engine OFF. This is a bulb test to ensure the MIL is able to illuminate.
2. The MIL turns OFF after the engine is started if a diagnostic fault is not present.
3. The MIL remains illuminated after the engine is started if the control module detects a fault. A diagnostic trouble code (DTC) is stored any time the control module illuminates the MIL due to an emissions related fault.
4. The MIL turns OFF after three consecutive ignition cycles in which a "Test Passed" has been reported for the diagnostic test that originally caused the MIL to illuminate.
5. The MIL flashes if the control module detects a misfire condition which could damage the catalytic converter.
6. When the MIL is illuminated and the engine stalls, the MIL will remain illuminated as long as the ignition is ON.
7. When the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition is cycled OFF and then ON.

Trip

A trip is an interval of time during which the diagnostic test runs. A trip may consist of only a key cycle to power up the PCM, allow the diagnostic to run, then cycle the key OFF to power down the PCM. A trip may also involve a PCM power up, meeting specific conditions to run the diagnostic test, then powering down the PCM. The definition of a trip depends upon the diagnostic. Some diagnostic tests run only once per trip (i.e., catalyst monitor) while other tests run continuously during each trip (i.e. misfire).

Warm-Up Cycle

The PCM uses warm-up cycles to run some diagnostics and to clear any Diagnostic Trouble Codes (DTCs). A warm-up cycle occurs when the engine coolant temperature increases 40°F (22°C) from the start-up temperature. The engine coolant must also achieve a minimum temperature of 160°F (71°C). The PCM counts the number of warm-up cycles in order to clear the Malfunction Indicator Lamp (MIL). The PCM will clear the DTCs when 40 consecutive warm-up cycles occur without a malfunction.

Diagnostic Trouble Codes (DTCs)

The PCM is programmed with test routines that test the operation of the various systems the PCM controls. Some tests monitor internal PCM functions. Many tests are run continuously. Other tests run only under specific conditions, referred to as "Conditions for Running the DTC". When the vehicle is operating within the conditions for running a particular test, the PCM monitors certain parameters and determines if the values are within an expected range. The parameters and values considered outside the range of normal operation are listed as "Conditions for Setting the DTC". When the "Conditions for Setting the DTC" occur, the PCM executes the "Action Taken When the DTC Sets". Some DTCs alert the driver via the MIL or a message. Other DTCs do not trigger a driver warning, but are stored in memory. The PCM also saves data and input parameters when most DTCs are set. This data is stored in the Freeze Frame and/or Failure Records.

The DTCs are categorized by type. The DTC type is determined by the MIL operation and the manner in which the fault data is stored when a particular DTC fails. In some cases there may be exceptions to this structure. Therefore, when diagnosing the system it is important to read the "Action Taken When the DTC Sets" and the "Conditions for Clearing the DTC" in the supporting text.

There are different types of DTCs and different actions taken when the DTCs set. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

DTC Status

When the scan tool displays a DTC, the status of the DTC is also displayed. The following DTC statuses are indicated only when they apply to the DTC that is set.

1. Fail This Ign. (Fail This Ignition) Indicates that this DTC failed during the present ignition cycle.
2. Last Test Fail Indicates that this DTC failed the last time the test ran. The last test may have run during a previous ignition cycle if an A or B type DTC is displayed. For type C DTCs, the last failure must have occurred during the current ignition cycle to appear as Last Test Fail.
3. MIL Request Indicates that this DTC is currently requesting the MIL. This selection will report type B DTCs only when they have requested the MIL (failed twice).
4. Test Fail SCC (Test Failed Since Code Clear) Indicates that this DTC that has reported a failure since the last time DTCs were cleared.
5. History Indicates that the DTC is stored in the PCM History memory. Type "B" DTCs will not appear in History until they have requested the MIL (failed twice). History will be displayed for all type "A" DTCs and type "B" DTCs (which have requested the MIL) that have failed within the last 40 warm-up cycles. Type "C" DTCs that have failed within the last 40 warm-up cycles will also appear in History.
6. Not Run SCC (Not Run Since Code Clear) DTCs will be listed in this category if the diagnostic has not run since DTCs were last cleared. This status is not included with the DTC display since the DTC can not be set if the diagnostic has not run. This information is displayed when DTC Info is requested using the scan tool.

LIMP-IN MODE

If sensor input signals are missing or inadequate for transaxle operation, PCM will output preset operating signals to transaxle. Limp-in mode will keep vehicle operational and allow it to be driven with reduced transaxle function and performance to a repair facility. Malfunction Indicator Light (MIL) may illuminate if malfunction occurs. Vehicle should not be driven for extended periods in limp-in mode.

ELECTRONIC CONTROL SYSTEM

Note. Faulty engine sensors and actuators may cause transaxle-related DTCs or driveability problems. Engine faults and related DTCs must be diagnosed and repaired before transaxle DTCs are repaired. For additional information on diagnosing and repairing engine-related DTCs, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

Note. Stored DTCs may be retrieved from PCM memory using a factory recommended scan tool. DTCs cannot be retrieved by grounding 16-pin Data Link Connector (DLC). Connecting scan tool into DLC (located under left side of instrument panel) enables user to read DTCs and check system voltages on serial data line.

PCM constantly monitors all electrical circuits. If PCM detects circuit problems or sensors out of range, it will record a DTC. If problem continues for a predetermined time, MIL will illuminate.

If MIL is illuminated, DTC(s) are currently being detected. If MIL is OFF, and PCM has detected a circuit or sensor problem, DTC(s) will be stored in computer memory.

SHIFT INTERLOCK SYSTEM

Note. For system description and repair information, see appropriate SHIFT INTERLOCK SYSTEMS article.

TROUBLE SHOOTING

Note. Any diagnosis should begin with confirming the customer's complaint. If possible, road test vehicle first, and note transaxle performance for future reference during diagnosis.

PRELIMINARY INSPECTION

Transaxle malfunctions may be caused by poor engine performance, improper adjustments or failure of hydraulic, mechanical or electronic components. Prior to diagnosing transaxle concerns, always begin by checking fluid level, fluid condition and shift cable adjustment. Ensure engine starts with gearshift lever in Park and Neutral to ensure proper adjustment of Park/Neutral Position (PNP) switch. Ensure all system-related fuses are okay. Check wire harnesses for proper routing. Verify all harness and component connections are clean and tight. See WIRING DIAGRAMS . If area of fault cannot be located or repaired during preliminary inspection, check self-diagnostic system. See SELF-DIAGNOSTIC SYSTEM . Repair as necessary.

Perform road test to determine if problem has been corrected. See ROAD TEST under PERFORMANCE TESTS. If problem still exists, diagnose by symptom. See SYMPTOM DIAGNOSIS .

SYMPTOM DIAGNOSIS

Note. Perform PRELIMINARY INSPECTION prior to diagnosing by symptom.

Note. Use the following symptoms to aid in preliminary diagnosis. If a listed symptom matches the customer's concern, check the applicable items for possible cause.

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CLUTCH & BAND APPLICATIONS

CLUTCH & BAND APPLICATIONS

Fluid Conditions

Note. DO NOT replace the torque converter.

1. If transmission fluid is oxidized/discolored and no metal debris is found, but there is clutch fiber material, check transmission fluid. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
2. If transmission fluid is contaminated with engine coolant/oil, replace the torque converter. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article. NOTE: DO NOT replace the torque converter for other transmission component damage.
3. If transmission fluid is contaminated with sludge/metal particles, check for pump damage, drive sprocket support damage, turbine/stator shaft damage and no damage found in transmission. Replace the torque converter if the following conditions were found. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.
4. If fluid leaks from torque converter, perform the powder/dye leak check. Replace the torque converter if there is a leak present at weld areas, hub surface is damaged or bushing is damaged. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.

Function/Appearance Conditions

Note. If torque converter requires replacement, see REMOVAL & INSTALLATION - CENTURY & REGAL article.

1. If torque converter is discolored/overheated, replace the torque converter.
2. If broken/cracked flexplate, replace the torque converter.
3. If stripped converter bolt holes, replace the torque converter.
4. If torque converter pilot damaged, replace the torque converter.
5. If torque converter ballooning, replace the torque converter if end play exceeds .3 INCH (.7 mm) using Converter End Play Checker (J 35138).

Driveability Conditions (Non TCC)

1. If there are harsh gear shifts, see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis). DO NOT replace the torque converter.
2. If there is no drive/slips in drive (Scheme 277)to repair driveability. DO NOT replace the torque converter until completing all engine and transmission diagnostics.
3. If there is a idle surge/rough idle, see appropriate article in ENGINE PERFORMANCE. DO NOT replace the torque converter.
4. If there is poor acceleration above 30 mph (48 km/h) (Launch), see appropriate article in ENGINE PERFORMANCE or see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis). DO NOT replace the torque converter until completing all engine and transmission diagnostics.
5. If DTC P0741 (TCC Stuck OFF/High Slip) is present, see «DTC P0741: TCC SYSTEM STUCK OFF»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__dtc-p0741-tcc-system-stuck-off). DO NOT replace the torque converter if the code is intermittent.
6. If DTC P0742 (TCC Stuck ON) is present, see «DTC P0742: TCC SYSTEM STUCK ON»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__dtc-p0742-tcc-system-stuck-on). DO NOT replace the torque converter.
7. If DTC P1887 (TCC Release Switch) is present, see «DTC P1887: TORQUE CONVERTER CLUTCH RELEASE SWITCH CIRCUIT MALFUNCTION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__dtc-p1887-torque-converter-clutch-release). DO NOT replace the torque converter.
8. If there is a TCC apply/release shudder (Scheme 310)to repair problem.
9. If there is a TCC chuggle, see appropriate article in ENGINE PERFORMANCE or see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis).

Noise & Vibration Condition

1. If there is a noise or whine, see appropriate article in ENGINE PERFORMANCE or see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis) .
2. If there is a vibration or out of balance, see «FLEXPLATE/TORQUE CONVERTER VIBRATION TEST»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under PERFORMANCE TESTS or see appropriate article in ENGINE PERFORMANCE.

Isolating Vibration

Note. Some engine/transaxle combinations cannot be balanced in this manner due to limited clearances between the torque converter bolts and the engine. Ensure that the bolts do not bottom out in the lug nuts or the torque converter cover could be dented and cause internal damage.

Note. To isolate and correct a flywheel or torque converter vibration, separate the torque converter from the flywheel to determine if vibration is in the engine or transmission.

1. With the engine at idle speed and the transmission in Park or Neutral, observe the vibration.
2. Turn the engine OFF.
3. Raise and suitably support the vehicle.
4. Remove the transmission converter cover bolts and the cover. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.
5. Mark the relationship of the converter to the flywheel.
6. Remove the bolts attaching the converter to the flywheel. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.
7. Slide the torque converter away from the flywheel.
8. Rotate the flywheel and torque converter to inspect for defects or missing balance weights.
9. Lower the vehicle.
10. With the engine at idle speed and the transmission in Park or Neutral, observe the vibration. See appropriate article in ENGINE PERFORMANCE.
11. Turn the engine OFF.

Indexing Torque Converter

Note. 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 flywheel balance.

1. Raise and suitably support the vehicle.
2. Rotate the torque converter one bolt position.
3. Align the torque converter hub (2) in the engine crankshaft (3) and install the torque converter to flywheel bolts. (Scheme 312) See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.
4. Lower the vehicle.
5. With the engine at idle speed and the transmission in Park or Neutral, observe the vibration. See appropriate article in ENGINE PERFORMANCE. Repeat this procedure until you obtain the best possible balance.
6. Install the transmission converter cover bolts and the cover. See «REMOVAL & INSTALLATION - CENTURY & REGAL»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-removal-installation) article.

Scheme 312

The following test provides a method of evaluating the condition of the automatic transaxle. 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 Detent Downshifts
4. Full Throttle Detent Downshifts
5. Manual Downshifts
6. Coasting Downshifts
7. Manual Gear Range Selection

Before the road test, ensure the following

1. The engine is performing properly.
2. Transmission fluid level is correct.
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 assistant to operate the vehicle safely.
5. Observe any unusual sounds or smells.

After the road test, check the following

1. Transmission fluid level.
2. Diagnostic Trouble Codes (DTC) that may have set during the testing.
3. Scan tool data for any abnormal readings or data.

Electrical Function Check

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

Perform this check first, to ensure the electronic transaxle components are connected and functioning properly. If these components are not checked, a simple electrical condition could be mis-diagnosed.

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. Data that is questionable may indicate a concern. Engine Speed Transaxle Input Speed (turbine) Transaxle Output Speed Vehicle Speed Transmission Fluid Pressure (TFP) Manual Valve Position Switch Transaxle Range Commanded Gear (current gear) Pressure Control (PC) Solenoid Reference Current PC Solenoid Actual Current PC Solenoid Duty Cycle Brake Switch Engine Coolant Temperature Transmission Fluid Temperature Throttle Angle Ignition Voltage 1-2 Shift Solenoid 2-3 Shift Solenoid TCC Solenoid Duty Cycle TCC Slip Speed
5. Monitor the brake switch signal while depressing and releasing the brake pedal. The scan tool should display: CLOSED when the brake pedal is released. OPEN when the brake pedal is depressed.
6. Check the garage shifts as follows: 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. Pause 2 to 3 seconds in each gear position. Verify the gear engagements are immediate and not harsh. NOTE: Harsh engagement may be caused by any of the following conditions: High idle speed. Compare engine idle speed to desired idle speed. Commanded low PC solenoid current. Compare PC solenoid reference current to PC solenoid actual current. A default condition caused by certain DTCs that result in maximum line pressure to prevent slippage. NOTE: Soft or delayed engagement may be caused by any of the following conditions: Low idle speed. Compare engine idle speed to desired idle speed. Low fluid level. Commanded high PC solenoid current. Compare PC solenoid reference current to PC solenoid actual current. Cold transmission fluid. Check for low transmission fluid temperature.
7. Monitor transaxle range on the scan tool as follows: Apply the brake pedal and ensure the parking brake is set. Move the gear selector through all ranges. Pause 2-3 seconds in each range. Return gear selector to Park. Verify that all selector positions match the scan tool display.
8. Check throttle angle input as follows: Apply the brake pedal and ensure the parking brake is set. Ensure the gear selector is in Park. Monitor throttle angle while increasing and decreasing engine speed with the throttle pedal. The throttle angle displayed by scan tool should increase and decrease with engine speed.

Upshift Control & Torque Converter Clutch Apply

The PCM calculates the upshift points based primarily on two inputs: throttle angle and vehicle speed. When the PCM determines that conditions are met for a shift to occur, the PCM commands the shift by closing or opening the ground circuit for the appropriate solenoid.

1. Choose a throttle position of 12, 25 or 50 percent. See «SHIFT SPEED SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__shift-speed-specifications) . All throttle angles shown should be tested to cover the normal driving range.
2. Monitor the following scan tool parameters: Throttle Angle Vehicle Speed Engine Speed Commanded Gear Slip Speed Solenoid States
3. Place the gear selector in the O/D position.
4. Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
5. As the transaxle upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1 to 2 seconds of the commanded gear change.
6. Compare the shift speeds to the shift speed chart. See «SHIFT SPEED SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__shift-speed-specifications) . Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls. Note any harsh, soft or delayed shifts or slipping. Note any noise or vibration.
7. Repeat steps 1 - 6 to complete testing for all throttle angles.
8. Check for TCC apply in 3rd and 4th gear. Note the TCC apply point. When the TCC applies, there should be a noticeable drop in engine speed and a drop in slip speed displayed by scan tool to below 100 RPM. If the TCC apply can not be detected, check for DTCs. For TCC apply speeds, see «SHIFT SPEED SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__shift-speed-specifications) . Lightly tap and release the brake pedal. The TCC will release on most applications.

Part Throttle Detent Downshift

1. Place the gear selector in the O/D position.
2. Accelerate the vehicle to 40-55 MPH in 4th gear.
3. Quickly increase throttle angle to greater than 50 percent.
4. Verify the following: The TCC releases. The transaxle downshifts immediately to 3rd gear.

Full Throttle Detent Downshift

1. Place the gear selector in the O/D position.
2. Accelerate the vehicle to speeds of 40-55 MPH in 4th gear.
3. Quickly increase throttle angle to 100 percent.
4. Verify the following: The TCC releases. The transaxle downshifts immediately to 2nd gear.

Manual Downshifts

The shift solenoid valves do not control the 4-3 manual downshift. The 4-3 manual downshift is hydraulically controlled. The 3-2 and 2-1 manual downshifts are electronically controlled. The solenoid states will change during or shortly after a 4-3 downshift is selected.

4-3 Downshift

1. Place the gear selector in the O/D position. Accelerate the vehicle to 40-55 MPH in 4th gear. Release the throttle while moving the gear selector to 3rd.
2. Verify the TCC releases, the transaxle downshifts immediately to 3rd gear, and the engine slows the vehicle.

4-2 Downshift

1. Place the gear selector in the O/D position. Accelerate the vehicle to 40-45 MPH. Release the throttle while moving the gear selector to 2nd.
2. Verify the TCC releases, the transaxle downshifts immediately to 2nd gear, and the engine slows the vehicle.

4-1 Downshift

1. Place the gear selector in the O/D position. Accelerate the vehicle to 40 MPH. Release the throttle while moving the gear selector to 1st.
2. Verify the TCC releases, the transaxle downshifts immediately to 2nd gear, the engine slows the vehicle, and the transaxle downshifts to 1st gear at the calibrated speed, typically 30-40 MPH.

Coasting Downshifts

1. Place the gear selector in the O/D position. Accelerate the vehicle to 4th gear with the TCC applied. Release the throttle and lightly apply the brakes.
2. Verify the TCC releases, and downshifts occur at speeds shown in the shift speed chart. See «SHIFT SPEED SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__shift-speed-specifications) .

Manual Gear Range Selection

Note. Perform test using 10-15 percent throttle angle.

The shift solenoids control the upshifts in the manual gear ranges.

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

1. Manual 1st With the vehicle stopped, move the gear selector to 1st. Accelerate the vehicle to 20 MPH. Verify no upshifts occur, the TCC does not apply, and there is no noticeable slip, noise or vibration.

1. Manual 2nd With the vehicle stopped, move the gear selector to 2nd. Accelerate the vehicle to 35 MPH. Verify the 1-2 shift occurs, the 2-3 shift does not occur, and there is no noticeable slip, noise or vibration.

1. Manual 3rd With the vehicle stopped, move the gear selector to 3rd. Accelerate the vehicle to 40 MPH. Verify the 1-2 shift occurs, the 2-3 shift occurs, and there is no noticeable slip, noise or vibration.

SHIFT SPEED SPECIFICATIONS

Note. For shift speed specifications (Scheme 313)

Scheme 313

TORQUE CONVERTER DIAGNOSIS

The Torque Converter Clutch (TCC) is applied by fluid pressure, which is controlled by the PWM solenoid valve. This solenoid valve is located inside of the automatic transaxle assembly. The solenoid valve is controlled through a combination of computer controlled switches and sensors.

Torque Converter Stator

The torque converter stator roller clutch can have two different malfunctions

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

Poor Acceleration At Low Speed

If the stator is freewheeling at all times, the car tends to have poor acceleration from a standstill. At speeds above 30-35 MPH, the car may act normally. For poor acceleration, you should first determine that the exhaust system is not blocked, and the transaxle is in 1st gear when starting out from a stop.

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

If the stator is locked up at all times, performance is normal when accelerating from a standstill. Engine RPM and car speed are limited or restricted at high speeds. Visual examination of the converter may reveal a blue color from overheating.

If the converter has been removed, you can check the stator roller clutch by inserting a finger into the splined inner race of the roller clutch and trying to turn the race in both directions. You should be able to freely turn the inner race clockwise, but you should have difficulty in moving the inner race counterclockwise or unable to move the race at all.

Noise

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

You may notice a torque converter whine when the vehicle is stopped and the transaxle 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 both halves of the converter are turning at the same speed.

Perform a stall test to make sure the noise is actually coming from the converter

1. Place your foot on the brake.
2. Put the gear selector in Drive.
3. Depress the accelerator to approximately 1200 RPM for no more than 6 seconds. CAUTION: You may damage the transaxle if you depress the accelerator for more than 6 seconds.

A torque converter noise will increase under this load.

Torque Converter Clutch Shudder

The key to diagnosing TCC shudder is to note when it happens and under what conditions.

TCC shudder which is caused by the transaxle should only occur during the apply or the release of the converter clutch. Shudder should never occur after the TCC plate is fully applied.

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

1. An unknown condition is not allowing the clutch to become fully engaged.
2. An unknown condition is not allowing the clutch to release.
3. The clutch is releasing and applying at the same time.

One of the following conditions may be causing the problem to occur

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

If Shudder Occurs After TCC Has Applied

If shudder occurs after the TCC has applied, most of the time there is nothing wrong with the transaxle.

As mentioned above, the TCC is not likely to slip after the TCC has been applied. Engine problems may go unnoticed under light throttle and load, but they become noticeable after the TCC apply when going up a hill or accelerating. This is due to the mechanical coupling between the engine and the transaxle.

Once TCC is applied, there is no torque converter (fluid coupling) assistance. Engine or driveline vibrations could be unnoticeable before TCC engagement.

Inspect the following components in order to avoid misdiagnosis of TCC shudder. An inspection will also avoid the unnecessary disassembly of a transaxle or the unnecessary replacement of a torque converter.

1. Spark Plugs Inspect for cracks, high resistance or a broken insulator.
2. Plug Wires Look in each end. If there is red dust (ozone) or a black substance (carbon) present, then the wires are bad. Also look for a white discoloration of the wire. This indicates arcing during hard acceleration.
3. Coil Look for a black discoloration on the bottom of the coil. This indicates arcing while the engine is misfiring.
4. Fuel Injector The filter may be plugged.
5. Vacuum Leak The engine will not get a correct amount of fuel. The mixture may run rich or lean depending on where the leak occurs.
6. EGR Valve The valve may let in too much or too little non-combustible exhaust gas and could cause the engine to run rich or lean.
7. MAP/MAF Sensor Like a vacuum leak, the engine will not get the correct amount of fuel for proper engine operation.
8. Carbon On The Intake Valves Carbon restricts the proper flow of air/fuel mixture into the cylinders.
9. Flat Camshaft Valves do not open enough to let the proper fuel/air mixture into the cylinders.
10. Oxygen Sensor This sensor may command the engine too rich or too lean for too long.
11. Fuel Pressure This may be too low.
12. Engine Mounts Vibration of the mounts can be multiplied by TCC engagement.
13. Axle Joints Check for vibration.
14. TP Sensor The TCC apply and release depends on the TP sensor in many engines. If the TP sensor is out of specification, TCC may remain applied during initial engine loading.
15. Cylinder Balance Bad piston rings or poorly sealing valves can cause low power in a cylinder.
16. Fuel Contamination This causes poor engine performance.

HYDRAULIC PRESSURE TESTS

Note. Before performing a line pressure check, verify that the pressure control solenoid valve is receiving the correct electrical signal from the PCM.

Line Pressure

1. Install a scan tool.
2. Start the engine and set the parking brake.
3. Check for a stored DTC. See «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
4. Repair the vehicle, if necessary.
5. Check the transmission fluid level. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
6. Check the manual linkage for proper adjustment. See «ADJUSTMENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__adjustments) in SERVICING - CENTURY & REGAL article.
7. Turn the engine OFF. Remove the oil pressure test hole plug and install the Pressure Gauge (J 21867). (Scheme 314)
8. Put the gear selector in Park range and set the parking brake.
9. Start the engine and allow the engine to warm up at idle.
10. Access the Pressure Control (PC) solenoid valve control test on the scan tool.
11. Increase the PC solenoid actual current from zero to one amp in.1 amp increments. Allow the pressure to stabilize for five seconds after each pressure change. Read the corresponding line pressure on the pressure gauge.
12. Compare the data to the table. See «PC SOLENOID CURRENT & LINE PRESSURE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) table.
13. If pressure readings differ greatly from the table, see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis) under TROUBLE SHOOTING.
14. Shut the engine OFF. Remove the pressure gauge.
15. Apply sealant (GM P/N 12345382) to the oil pressure test hole plug.
16. Install the oil pressure test hole plug. Tighten the plug to specification. See «TORQUE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__torque-specifications).

PC SOLENOID CURRENT & LINE PRESSURE SPECIFICATIONS

Scheme 314

CLUTCH & SERVO AIR CHECKS

Note. For additional information, see COMPONENT DISASSEMBLY & REASSEMBLY in 4T65-E OVERHAUL article.

Circuit Description

The diagnostic system check is an organized approach to identify a problem condition created by an automatic transaxle. The diagnostic system check is the diagnostic starting point for an automatic transaxle complaint. The diagnostic system check directs you to the next logical step for diagnosing a transaxle concern. Perform this check only if there is a driveability complaint or if you have been directed here from another service information section.

Diagnostic Aids

Note. Do not clear the DTC unless directed by a diagnostic procedure. Clearing the DTC(s) will erase all freeze frame and failure records stored in PCM memory.

Note. Poor engine performance can sometimes be diagnosed as a transaxle driveability condition. To avoid mis-diagnosis of the automatic transaxle, always perform the diagnostic system check.

1. Use a scan tool that is known to function correctly. If necessary, test the scan tool on another vehicle. Ensure the scan tool contains the most current file available. The scan tool will display a loss of communication error message under the following conditions: The PCM power is interrupted. The ignition is turned OFF. The battery voltage level is very low. A poor connection at the Diagnostic Link Connector (DLC).

Test Description

The numbers listed below refer to step numbers in the diagnostic procedure

1. 1 - Determines if the scan tool is receiving power through the DLC connector.
2. 2 - MIL should illuminate whenever the ignition is ON and the engine is not running.
3. 3 - Determines if the PCM is transmitting class 2 serial data to the DLC and that the class 2 data circuit is not open or shorted.
4. 4 - Determines if a DTC is current or stored in history.

Diagnostic Procedure

1. Turn ignition ON, engine OFF. Does the scan tool turn ON? If so, go to next step. If not, diagnose scan tool concern. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. NOTE: Check for applicable service bulletins before proceeding with this diagnostic procedure. Perform this diagnostic procedure only if there is a driveability complaint or if you have been directed to this diagnostic procedure from another section in the service information. NOTE: Do not turn the ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure.
2. Is the MIL ON? If so, go to next step. If not, diagnose MIL concern. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
3. Attempt to establish communication with the PCM. Does the scan tool communicate with the PCM? If so, go to next step. If not, diagnose scan tool concern. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
4. Use the scan tool CAPTURE INFO function to save or capture (store information) any DTC information. Are there any DTCs present? If so, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__diagnostic-trouble-code-definitions) . If not, see «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis) under TROUBLE SHOOTING. NOTE: DTCs, engine performance, and transaxle default actions can greatly affect the transaxle performance. Ensure that these items are not the cause of a transaxle concern.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. Only transaxle-related DTCs are listed. For engine-related DTC definitions, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. These DTCs pertain to engine performance and must be repaired first, as engine performance and related component signals will affect transaxle operation and diagnosis.

DIAGNOSTIC TROUBLE CODE DEFINITIONS (1)

CLEARING DIAGNOSTIC TROUBLE CODES

Using scan tool, clear DTCs following scan tool manufacturer's instructions. Do not clear DTCs unless instructed to do so.

SUMMARY

Note. Always clear DTCs once repairs are complete. See CLEARING DIAGNOSTIC TROUBLE CODES . Road test vehicle and retrieve DTCs to determine if complaint or DTC is repaired.

If no hard DTCs are present, and driveability symptoms or intermittent DTCs exist, attempt diagnosis by symptom, or by testing individual components related to system fault. See TROUBLE SHOOTING and/or COMPONENT TESTS . If no problem is found, verify proper electronic control system circuit operation.

DTC P0218: TRANSAXLE FLUID OVERTEMPERATURE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Transmission fluid is drawn from the bottom pan through the filter, case assembly, channel plate assembly, control valve body assembly and into the oil pump assembly. The pump is mounted on the control valve body assembly. Fluid pressure leaving the pump is controlled by the pressure regulator valve and becomes the main supply of line pressure to the various components and hydraulic circuits.

Hot fluid from the torque converter flows through the TCC control valve into the cooler lines to the oil cooler located in the vehicle radiator (and auxiliary cooler if equipped). Cool fluid then returns to lubricate the final drive assembly and other components along the output shaft.

If the PCM detects a high temperature on the TFT sensor circuit for an extended period of time, then DTC P0218 sets. DTC P0218 is a type "C" DTC.

Conditions For Running DTC P0128

DTC will run under the following condition

1. No TFT sensor DTC P0711, P0712 or P0713.

Conditions For Setting DTC P0128

DTC will set under the following condition

1. The transmission fluid temperature is greater than 266°F (130°C) for 10 minutes.

Action Taken By PCM

PCM performs the following actions if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM freezes shift adapts.
3. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame records.
4. The PCM stores DTC P0218 in PCM history.

Conditions for Clearing DTC P0128

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - This step ensures that the transmission fluid is at the proper level. A low fluid level may cause an overtemperature condition.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the Failure Records. Clear the DTCs. Perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article. When done, go to next step. NOTE: Before clearing the DTC, use the scan tool to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Inspect for the following conditions: Engine overheating due to low coolant level or restricted air flow. Transmission fluid flow through cooler and/or auxiliary cooler (if equipped) is restricted due to low transmission fluid level, clogged filter, or leaking filter or seal. Plugged, kinked or damaged transmission fluid cooler pipes. Air flow through transmission fluid cooler and/or auxiliary cooler (if equipped) is restricted due to damaged fins or debris. Line pressure low. See «HYDRAULIC PRESSURE TESTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__hydraulic-pressure-tests) under PERFORMANCE TESTS. Did you find and repair the condition? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
4. Perform the following procedure to verify the repair: Install a scan tool. Select DTC. Select Clear Info. Start and run the engine until it engine reaches normal operating temperature. Select ENGINE RUN TIME and TRANS FLUID TEMP on the scan tool. Drive the vehicle for 15 minutes. Ensure that the transmission fluid temperature has stabilized and is less than 264°F (129°C). Select SPECIFIC DTC. Enter DTC P0218. Has the test run and passed? If so, proceed to next step. If not, go to step 2 .
5. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in O/D.

DTC P0502: VEHICLE SPEED SENSOR CIRCUIT (LOW INPUT)

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Note. The Vehicle Speed Sensor (VSS) may also be referred to as the Output Speed Sensor (OSS).

The VSS system is a pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed VSS reluctor wheel, which is pressed onto the final drive carrier assembly. As the vehicle drives forward, the VSS reluctor wheel rotates. This rotation produces a variable AC signal in the pickup coil that is proportional to vehicle speed. The PCM uses this signal to calculate vehicle speed, shift timing and gear ratios.

If the PCM detects a low vehicle speed with a high engine speed while in a drive range, then DTC P0502 sets. DTC P0502 is a type "B" DTC.

Conditions For Running DTC P0502

DTC will run under the following conditions

1. No MAP sensor DTC P0107 or P0108.
2. No TP sensor DTC P0121, P0122 or P0123.
3. No ISS DTC P0716 or P0717.
4. The throttle angle is greater than 12 percent.
5. The engine torque is 40-300 ft. lbs. (55-400 N.m).
6. The input shaft speed is greater than 1500 RPM.

Conditions For Setting DTC P0502

DTC will set under the following condition

1. The output shaft speed is less than 150 RPM for 2.5 seconds.

The PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM calculates vehicle speed from the input shaft speed sensor for shift timing.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0502 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions for Clearing DTC P0502

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step tests the ability of the VSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.
2. 4 - This step tests the VSS circuit for correct resistance.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record freeze frame and failure records for reference. Clear DTCs. Raise and support the drive wheels. Start and idle the engine. Place the gearshift lever in Drive. Monitor OSS on the scan tool. With the drive wheels rotating, increase and decrease the throttle position. Does OSS RPM increase when wheel speed increases? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step. CAUTION: Support the lower control arms in the normal horizontal position to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.
3. Turn ignition OFF. Disconnect the PCM connector C1. Using Connector Test Adapter Kit (J 35616-A), connect DMM between PCM harness connector C1 terminals No. 64 and 65. Select AC volts on DMM. Turn ignition ON, engine OFF. Place gearshift lever in Drive or Neutral. Rotate right front drive wheel by hand, while observing the DMM. Does the voltage measure greater than .4 volts AC? If so, go to step 15 . If not, go to next step.
4. Leave the DMM connected between PCM harness connector C1 terminals No. 64 and 65. Select ohms on the DMM. Measure the resistance of complete VSS circuit. Is the circuit resistance within 1650-3180 ohms? If so, go to step 8 . If not, go to next step.
5. Is the circuit resistance within 1650-3180 ohms? If so, go to step 11 . If not, go to next step.
6. Leave the DMM test leads connected between PCM harness connector C1 terminals No. 64 and 65. Disconnect the VSS connector at transaxle. Test the high signal circuit (CKT 400) and the low signal circuit (CKT 401) of the VSS for a short together. Measure from PCM harness connector C1 terminals No. 64 and 65. Are the signal and ground circuits shorted together? If so, go to next step. If not, go to step 14 .
7. Repair short between the high signal circuit (CKT 400) and the low signal circuit (CKT 401). Did you complete the repair? If so, go to step 16 .
8. Test the high signal circuit (CKT 400) of the VSS for a short to ground between PCM and VSS. Did you find and correct the condition? If so, go to step 16 . If not, go to step 15 .
9. Reconnect PCM connector C1. Select DC volts on the DMM. Using the connector test adapter, connect DMM between terminals "A" and "B" of the VSS vehicle harness. Turn ignition ON, engine OFF. Does DMM display greater than 1.0 volt. If so, go to next step. If not, go to step 13 .
10. Repair short to power in the high signal circuit (CKT 400). Did you complete the repair? If so, go to step 16 .
11. Test the high signal circuit (CKT 400) of the VSS for an open between the PCM and the VSS. Did you find and correct the condition? If so, go to step 16 . If not, go to next step.
12. Test the low signal circuit (CKT 401) of the VSS for an open between the PCM and the VSS. Did you find and correct the condition? If so, go to step 16 . If not, go to step 14 .
13. Remove the VSS. Inspect the VSS and the transaxle for the following: Incorrect VSS or VSS damage. Excessive runout in the final drive carrier assembly. Excessive VSS to speed sensor rotor gap. Incorrect speed sensor rotor alignment. Speed sensor rotor damage. Repair any of the above items as necessary. Did you find and correct the condition? If so, go to step 16 . If not, go to next step.
14. Replace the VSS. See «VEHICLE SPEED SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 16 .
15. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
16. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle. Ensure output shaft speed is greater than 250 RPM for at least 2 seconds. Select SPECIFIC DTC. Enter DTC P0502. Has the test run and passed? If so, go to next step. If not, go to step 2 .
17. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

DTC P0503: VEHICLE SPEED SENSOR CIRCUIT PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Note. The Vehicle Speed Sensor (VSS) may also be referred to as the Output Speed Sensor (OSS).

The VSS system is a pulse generator consisting of a speed sensor assembly, located in the case extension, and a toothed VSS reluctor wheel, which is pressed onto the final drive carrier assembly. As the vehicle drives forward, the VSS reluctor wheel rotates. This rotation produces a variable AC signal in the pickup coil that is proportional to vehicle speed. The PCM uses this signal to calculate vehicle speed, shift timing and gear ratios.

If the PCM detects a large change in vehicle speed in a short period of time, then DTC P0503 sets. DTC P0503 is a type "B" DTC.

Conditions For Running DTC P0503

DTC will run under the following conditions

1. No VSS DTC P0502.
2. The engine speed is more than 500 RPM for 5 seconds and not in fuel shut-off.
3. The transaxle is not in Park or Neutral.
4. The time since last gear range change is more than 6 seconds.
5. No output shaft speed rise greater than 250 RPM in 2 seconds.

Conditions For Setting DTC P0503

DTC will set under the following condition

1. The output shaft speed drops greater than 1500 RPM in 3 seconds.

PCM performs the following if DTC is set

1. The PCM illuminates MIL during second consecutive trip in which conditions for setting DTC are met.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM calculates vehicle speed from input shaft speed sensor for shift timing.
5. The PCM records operating conditions when conditions for setting DTC are met. PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0503 in PCM history during second consecutive trip in which conditions for setting DTC are met.

Conditions for Clearing DTC P0503

DTC will clear under the following conditions

1. The PCM turns OFF MIL during third consecutive trip in which diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears DTC from PCM history if vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels DTC default actions when ignition is OFF long enough to power down PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step tests ability of VSS to produce AC voltage. This step also verifies integrity of wiring to PCM.
2. 4 - This step tests VSS circuit for correct resistance.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing DTCs, use scan tool to record freeze frame and failure records for reference. Clear DTCs. Raise and support drive wheels. Start and idle the engine. Place transaxle in Drive. Monitor OSS on the scan tool. With drive wheels rotating, increase and decrease throttle position. Does OSS RPM increase when wheel speed increases? If so, see appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If not, go to next step. CAUTION: Support lower control arms in normal horizontal position to avoid damage to drive axles. DO NOT operate vehicle in gear with wheels hanging down at full travel.
3. Turn ignition OFF. Disconnect PCM connector C1. Using Connector Test Adapter Kit (J 35616-A), connect DMM between PCM connector C1 terminals No. 64 and 65. Select AC volts on DMM. Turn ignition ON, engine OFF. Place gearshift lever in a Drive or Neutral. Rotate right front drive wheel by hand, while observing the DMM. Does the voltage measure greater than .4 volt AC? If so, go to step 8 . If not, go to next step.
4. Leave the DMM test leads connected between PCM connector C1 terminals No. 64 and 65. Select ohms on DMM. Measure resistance of complete VSS circuit. Is circuit resistance within 1650-3180 ohms? If so, go to step 9 . If not, go to next step.
5. Is circuit resistance greater than 3180 ohms? If so, go to step 11 . If not, go to next step.
6. Leave DMM test leads connected between PCM connector C1 terminals No. 64 and 65. Disconnect VSS connector at transaxle. Test high signal circuit (CKT 400) and low signal circuit (CKT 401) of VSS for a short together. Are signal and ground circuits shorted together? If so, go to next step. If not, go to step 14 .
7. Repair short between high signal circuit (CKT 400) and low signal circuit (CKT 401). Did you complete the repair? If so, go to step 16 .
8. Test high signal circuit (CKT 400) of VSS for short to ground between PCM and VSS. Did you find and correct condition? If so, go to step 16 . If not, go to step 15 .
9. Reconnect PCM connector C1. Select DC volts on DMM. Using connector test adapter kit, connect DMM between terminals "A" and "B" of VSS vehicle harness. Turn ignition ON, engine OFF. Does DMM display greater than 1.0 volt? If so, go to next step. If not, go to step 13 .
10. Repair short to power in high signal circuit (CKT 400). Did you complete the repair? If so, go to step 16 .
11. Test high signal circuit (CKT 400) of VSS for an open between PCM and VSS. Did you find and correct condition? If so, go to step 16 . If not, go to next step.
12. Test low signal circuit (CKT 401) of the VSS for an open between the PCM and the VSS. Did you find and correct condition? If so, go to step 16 . If not, go to step 14 .
13. Remove the VSS. See «VEHICLE SPEED SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing) under REMOVAL & INSTALLATION in SERVICING - CENTURY & REGAL article. Inspect VSS and transaxle for the following: Incorrect VSS. VSS damage. Excessive runout in final drive carrier assembly. Excessive VSS to speed sensor rotor gap. Incorrect speed sensor rotor alignment. Speed sensor rotor damage. Repair any of the above items as necessary. Did you find and correct condition? If so, go to step 16 . If not, go to next step.
14. Replace the VSS. See «VEHICLE SPEED SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 16 .
15. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
16. Perform the following procedure to verify the repair: Using a scan tool, select DTC. Select Clear Info. Drive vehicle. Ensure output shaft speed is greater than 300 RPM for at least 2 seconds. Select SPECIFIC DTC. Enter DTC P0503. Has test run and passed? If so, go to next step. If not, go to step 2 .
17. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

DTC P0711: TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor. When the transmission fluid is cold, the sensor resistance is high. As the transmission fluid warms up, the sensor resistance decreases. This diagnostic monitors the TFT sensor circuit. The circuit may be functional but not in the normal operating range. This diagnostic indicates stuck, erratic, intermittent, or skewed values, resulting in reduced system performance. The TFT sensor range is -40°F to 304°F (-40°C to 151°C).

If the PCM detects an intermittent voltage or no voltage change in the TFT sensor circuit, then DTC P0711 sets. DTC P0711 is a type "C" DTC.

Conditions For Running DTC P0711

DTC will run under the following conditions

1. No engine coolant temperature DTC P0117 or P0118.
2. No VSS DTC P0502 or P0503.
3. No ISS DTC P0716 or P0717.
4. The engine coolant temperature is 158°F (70°C) or more.
5. The engine coolant temperature has changed by 90°F (50°C) or more since start-up.
6. The engine run time is more than 5 minutes.
7. The TFT sensor voltage is .2-4.92 volts.
8. The transmission fluid temperature at start-up is -40°F to 69°F (-40°C to 21°C).
9. The vehicle speed is greater than 5 MPH for at least 6 minutes and 49 seconds cumulative.
10. The TCC slip is greater than 80 RPM for at least 6 minutes and 49 seconds cumulative.

Conditions For Setting DTC P0711

DTC will set under the following conditions

1. Condition 1 - The change in transmission fluid temperature is less than 2°F (1.5°C) since start-up for at least 6 minutes and 49 seconds continuous.
2. Condition 2 - The change in transmission fluid temperature is greater than 36°F (20°C) within .2 seconds and this occurs at least 14 times within 7 seconds.

PCM performs the following if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM freezes shift adapts.
3. The PCM calculates a default transmission fluid temperature from the engine coolant temperature sensor and the intake air temperature sensor.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P0711 in PCM history.

Conditions for Clearing DTC P0711

DTC P0711 will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step attempts to repeat the condition that set the DTC.
2. 5 - This step attempts to repeat the condition in the engine wiring harness.
3. 6 - This step determines if a condition exists with the PCM or TFT sensor.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTC. Record the temperature at the start and end of the trip. Drive the vehicle for at least 7 minutes. Using a scan tool, observe TRANS FLUID TEMP for rapid fluctuations in temperature. Record the temperature at the start and end of the trip. Did you record the temperatures? If so, go to next step.
4. Did the transmission fluid temperature rise more than 2.7°F (1.5°C)? If so, go to next step. If not, go to step 6 .
5. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Install the Jumper Harness (J 44152) on the engine side of the transaxle in-line 20-pin connector. Install a 12-volt test light between terminals "L" and "M" of the transaxle in-line 20-pin connector using a Connector Test Adapter Kit (J 35616-A). Turn ON the ignition switch with the engine OFF. While observing the TRANS FLUID TEMP parameter on the scan tool, massage the engine wiring harness from the PCM connectors to the transaxle in-line 20-pin connector. Does the transmission fluid temperature change by more than 36°F (20°C) in .20 seconds? If so, go to step 7 . If not, go to step 9 .
6. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Turn ignition ON, engine OFF. With a scan tool, observe the TRANS FLUID TEMP parameter. Does the transmission fluid temperature change more than 2.7°F (1.5°C) when the transaxle in-line 20-pin connector is disconnected? If so, go to step 12 . If not, go to step 13 .
7. Test the signal circuit (CKT 1227) of the TFT sensor for an intermittent open or short to ground between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 14 . If not, go to next step.
8. Test the low reference circuit (CKT 2762) of the TFT sensor for an intermittent open or short to ground between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 14 . If not, go to step 13 .
9. Test the signal circuit (CKT 1227) of the TFT sensor for an intermittent open or short to ground between the transaxle in-line 20-pin connector and the TFT sensor. Did you find the condition? If so, go to step 11 . If not, go to next step.
10. Test the low reference circuit (CKT 452) of the TFT sensor for an intermittent open or short to ground between the transaxle in-line 20-pin connector and the TFT sensor. Did you find the condition? If so, go to next step. If not, go to step 12 .
11. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 14 .
12. Replace the TFT sensor. See «TRANSMISSION FLUID TEMPERATURE SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 14 .
13. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
14. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle from a cool start, for at least 5 minutes. The rise in transmission fluid temperature must be at least 5.4°F (3°C) since start up, and the change in transmission fluid temperature must not be greater than 36°F (20°C) in .2 seconds for 14 times in 7 seconds. Select SPECIFIC DTC. Enter DTC P0711. Has the test run and passed? If so, go to next step. If not, go to step 2 .
15. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

DTC P0712: TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (LOW INPUT)

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The PCM provides a 5-volt reference to the sensor circuit. A high fluid temperature or a short to ground on the sensor signal circuit results in low signal voltage. The TFT sensor operating range is -40°F to 304°F (-40°C to 151°C).

If the PCM detects a continuous short to ground in the TFT sensor circuit, then DTC P0712 sets. DTC P0712 is a type "C" DTC.

Conditions For Running DTC P0712

DTC will run under the following condition

1. The system voltage is 9-18 volts.

Conditions For Setting DTC P0712

DTC will set under the following condition

1. The PCM detects a TFT sensor voltage of less than .2 volts for 10 seconds.

PCM performs the following if DTC is set

1. The PCM does not turn ON the MIL.
2. The PCM freezes shift adapts.
3. The PCM calculates a default transmission fluid temperature from the engine coolant temperature sensor and the intake air temperature sensor.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P0712 in PCM history.

Conditions for Clearing DTC P0712

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - A value below.2 volts indicates the fault is present. A value above.2 volts indicates the fault is intermittent.
2. 3 - A value greater than 4.9 volts indicates the fault is in the transaxle side.
3. 5 - For resistance at other temperatures (Scheme 331)

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records. Using the Clear Info function erases the failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, observe the TFT sensor parameter. Does the scan tool indicate that the TFT sensor voltage is less than .2 volt? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs will set). Turn ignition ON, engine OFF. Observe the TFT sensor voltage. Does the scan tool indicate that the TFT sensor voltage is greater than 4.9 volts? If so, go to step 5 . If not, go to next step.
4. Test the signal circuit (CKT 1227) of the TFT sensor for a short to ground between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 11 . If not, go to step 10 .
5. Connect the Jumper Harness (J 44152) to the transaxle side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect DMM from terminals "L" to "M" of the jumper harness. Measure the resistance. Does the resistance measure within 3164-3867 ohms at 68°F (20°C) to 225-285 ohms at 190°F (88°C)? If so, go to next step. If not, go to step 7 .
6. Test the signal circuit (CKT 1227) of the TFT sensor for a short to ground between the transaxle in-line 20-pin connector and the TFT sensor. Was the condition found? If so, go to step 9 . If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
7. Disconnect the TFT sensor from the transaxle internal wiring harness. Using the DMM, measure the resistance between terminals "L" and "M" of the jumper harness. Was the condition found? If so, go to step 9 . If not, go to next step.
8. Replace the TFT sensor. See «TRANSMISSION FLUID TEMPERATURE SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 11 .
9. Replace the transaxle internal wiring harness. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 11 .
10. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
11. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Turn ignition ON, engine OFF. The transmission fluid temperature signal voltage must be greater than .2 volt for 10 seconds. Select SPECIFIC DTC. Enter DTC P0712. Has the test run and passed? If so, go to next step. If not, go to step 2 .
12. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

DTC P0713: TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (HIGH INPUT)

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor whose resistance value changes based on temperature. The PCM provides a 5-volt reference to the sensor. A low fluid temperature, an open TFT sensor or an open sensor circuit results in high signal voltage. The TFT operating range is -40°F to 304°F (-40°C to 151°C).

If the PCM detects a continuous open or a short to power on the TFT sensor circuit, then DTC P0713 sets. DTC P0713 is a type "C" DTC.

Conditions For Setting DTC P0713

DTC will run under the following conditions

1. The system voltage is 9-18 volts.
2. The ignition is ON.

DTC will set under the following conditions

1. The PCM detects a TFT sensor voltage greater than 4.9 volts for 6 minutes and 40 seconds continuous.

PCM performs the following if DTC is set

1. The PCM does not turn ON the MIL.
2. The PCM freezes shift adapts.
3. The PCM calculates a default transmission fluid temperature from the engine coolant temperature sensor and the intake air temperature sensor.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P0713 in PCM history.

Conditions For Clearing DTC P0713

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - A value of 4.9-5.0 volts indicates the PCM and engine side of the wiring are good.
2. 6 - A short to voltage greater than 5 volts would cause the TFT sensor to open.
3. 9 - A short to the TFT sensor signal circuit and any other circuits in the transaxle harness could cause the TFT sensor to open.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, observe the TFT sensor parameter. Does the scan tool display a TFT sensor voltage greater than 4.9 volts? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector. Connect the Jumper Harness (J 44152) to the engine side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a DMM from terminal "L" to terminal "M" of the jumper harness. Turn ignition ON, engine OFF. Observe the voltage on the DMM. Does the voltage measure within 4.9-5.0 volts? If so, go to step 7 . If not, go to next step.
4. Does the voltage in Step 3 measure more than 5.0 volts? If so, go to step 6 . If not, go to next step.
5. Test the signal circuit (CKT 1227) of the TFT sensor for an open between the PCM and the transaxle in-line 20-pin connector. Test the low reference circuit (CKT 2762) of the TFT sensor for an open between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 14 . If not, go to step 13 .
6. Test the signal circuit (CKT 1227) of the TFT sensor for a short to power between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 11 . If not, go to step 13 .
7. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Install the jumper harness on the transaxle side of the transaxle in-line 20-pin connector. Using the DMM, measure the resistance between terminals "L" and "M" of the jumper harness. Is the resistance less than 100 k/ohms? If so, go to step 9 . If not, go to next step.
8. Test the signal circuit (CKT 1227) of the TFT sensor for an open between the transaxle in-line 20-pin connector and the TFT sensor. Test the low reference circuit (CKT 452) of the TFT sensor for an open between the transaxle in-line 20-pin connector and the TFT sensor. Did you find the condition? If so, go to step 10 . If not, go to step 12 .
9. Measure the resistance between terminal "L" and all other terminals, except "M", of the jumper harness. Is the resistance between terminal "L" and all other terminals, except "M", greater than 1000 ohms? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
10. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
11. Was the engine harness repaired, or the transaxle harness replaced due to a short to power or other circuit? If so, go to next step. If not, go to step 14 .
12. Replace the TFT sensor. See «TRANSMISSION FLUID TEMPERATURE SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 14 .
13. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
14. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Turn ignition ON, engine OFF. The TFT sensor voltage must be less than 4.9 volts for at least 6 minutes and 40 seconds. Select SPECIFIC DTC. Enter DTC P0713. Has the test run and passed? If so, go to next step. If not, go to step 2 .
15. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

DTC P0716: INPUT SPEED SENSOR CIRCUIT PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Input Shaft Speed (ISS) sensor is a permanent magnet with a coil of wire wound around it. The ISS sensor mounts in the case cover facing the reluctor wheel of the input shaft. As the reluctor wheel is driven by the turbine shaft, an AC signal is induced in the input speed sensor. Higher vehicle speeds induce a higher frequency and voltage at the sensor.

There is a fixed air gap between the sensor and the teeth on the sensor reluctor wheel. The ISS sensor input is used by the PCM to control line pressure, TCC apply and release, and transaxle shift patterns. This sensor is also used to calculate the appropriate gear ratios and TCC slippage.

This DTC indicates stuck, erratic, or intermittent conditions in the system.

If the PCM detects an unrealistically large change in the ISS sensor high signal in a short period of time, then DTC P0716 sets. DTC P0716 is a type "B" DTC.

Conditions For Running DTC P0716

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0717 is set and DTC P0717 has passed this ignition cycle.
4. No 1-2 shift solenoid valve DTC P0751, P0752 or P0753.
5. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
6. The throttle angle is greater than 14 percent.
7. The vehicle speed is greater than 5 MPH.

Conditions For Setting DTC P0716

DTC will set under the following conditions

1. The input shaft speed changes by greater than 1300 RPM in .8 seconds.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM inhibits TCC.
3. The PCM freezes shift adapts.
4. The PCM inhibits 4th gear if the transaxle is in hot mode.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0716 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P0716

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - A Yes answer indicates that the transaxle side of the circuit is functioning properly.
2. 4 - Although the resistance is within specification in Step 3, there may be a short to ground or a short to power condition.
3. 8 - This step begins the transaxle harness diagnosis.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a Scan Tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Start and idle the engine in Park. With the scan tool, observe the ISS parameter. Does the scan tool display a input shaft speed greater than 100 RPM? If so, ensure engine wiring harness is not located near spark plug wires or DIS coils. See «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Connect the Jumper Harness (J 44152) to the transaxle side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect the DMM from terminal "S" to terminal "V" of the jumper harness. Measure the resistance. Is the resistance within 820-1428 ohms? If so, go to next step. If not, go to step 8 .
4. Leave one lead of the DMM connected to terminal "S" of the jumper harness. Using the other lead, test for a short between terminal "S" and all other terminals in the transaxle in-line 20-pin connector. Test for a short between terminal "S" and the transaxle case. Did you find the condition? If so, go to step 10 . If not, go to next step.
5. Test the high signal circuit (CKT 1230) of the ISS for an open, a short to ground, or a short to the low signal circuit (CKT 1231) between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to next step.
6. Turn ignition ON, engine OFF. Test the high signal circuit (CKT 1230) of the ISS for a short to power between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to next step.
7. Test the low signal circuit (CKT 1231) of the ISS for an open between the PCM connector and the transaxle 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to step 12 .
8. Test the high signal circuit (CKT 1230) of the ISS for an open or a short to the low signal circuit (CKT 1231) of the ISS between the transaxle in-line 20-pin connector and the sensor. Did you find the condition? If so, go to step 10 . If not, go to next step.
9. Test the low signal circuit (CKT 1231) of the ISS for an open between the transaxle in-line 20-pin connector and the sensor. Did you find the condition? If so, go to next step. If not, go to step 11 .
10. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 13 .
11. Replace the input shaft speed sensor. See «INPUT SHAFT SPEED SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 13 .
12. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
13. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park. The ISS must be greater than 500 RPM for one second. Select SPECIFIC DTC. Enter DTC P0716. Has the test run and passed? If so, go to next step. If not, go to step 2 .
14. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring harness for poor connections at ISS, transaxle in-line 20-pin connector and PCM. Check for bent, backed out or damaged terminals, or for poor terminal tension. Check for chafed wiring. When diagnosing an intermittent condition, wiggle wiring harness while observing scan tool for change in value. Inspect transaxle in-line 20-pin connector for transaxle fluid. Check for Electromagnetic Interference (EMI) in ISS signal and ground circuits. EMI may be induced by a misrouted wiring harness along spark plug wires.

DTC P0717: INPUT SPEED SENSOR CIRCUIT NO SIGNAL

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Input Shaft Speed (ISS) sensor is a permanent magnet with a coil of wire wound around it. The ISS sensor mounts in the case cover facing the reluctor wheel of the input shaft. As the reluctor wheel is driven by the turbine shaft, an AC signal is induced in the input speed sensor. Higher vehicle speeds induce a higher frequency and voltage at the sensor.

There is a fixed air gap between the sensor and the teeth on the sensor reluctor wheel. The ISS sensor input is used by the PCM to control line pressure, TCC apply and release, and transaxle shift patterns. This sensor is also used to calculate the gear ratios and TCC slippage.

If the PCM detects a low input speed while the vehicle and engine speeds are high, then DTC P0717 sets. DTC P0717 is a type "B" DTC.

Conditions For Running DTC P0717

DTC will run under the following conditions

1. No VSS DTC P0502 or P0503.
2. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
3. The vehicle speed is greater than 5 MPH.

Conditions For Setting DTC P0717

DTC will set under the following conditions

1. The input shaft speed is less than 100 RPM for 5 seconds.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM inhibits TCC.
3. The PCM freezes shift adapts.
4. The PCM inhibits 4th gear if the transaxle is in hot mode.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0717 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P0717

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - A Yes answer indicates that the transaxle side of the circuit is functioning properly.
2. 4 - Although the resistance is within specification in Step 3, there may be a short to ground or a short to power condition.
3. 8 - This step begins the transaxle harness diagnosis.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the "Clear Info" function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Start and idle the engine in Park. With the scan tool, observe the ISS parameter. Does the scan tool display a input shaft speed greater than 100 RPM. If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Connect the Jumper Harness (J 44152) to the transaxle side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect the DMM from terminal "S" to terminal "V" of the jumper harness. Measure the resistance. Is the resistance within 820-1428 ohms? If so, go to next step. If not, go to step 8 .
4. Leave one lead of the DMM connected to terminal "S" of the jumper harness. Using the other lead, test for a short between terminal "S" and all other terminals in the transaxle in-line 20-pin connector. Test for a short between terminal "S" and the transaxle case. Did you find the condition? If so, go to step 10 . If not, go to next step.
5. Test the high signal circuit (CKT 1230) of the ISS for an open, a short to ground, or a short to the low signal circuit (CKT 1231) between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to next step.
6. Turn ignition ON, engine OFF. Test the high signal circuit (CKT 1230) of the ISS for a short to power between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to next step.
7. Test the low signal circuit (CKT 1231) of the ISS for an open between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 13 . If not, go to step 12 .
8. Test the high signal circuit (CKT 1230) of the ISS for an open or a short to the low signal circuit (CKT 1231) of the ISS between the transaxle in-line 20-pin connector and the sensor. Did you find the condition? If so, go to step 10 . If not, go to next step.
9. Test the low signal circuit (CKT 1231) of the ISS for an open between the transaxle in-line 20-pin connector and the sensor. Did you find the condition? If so, go to next step. If not, go to step 11 .
10. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 13 .
11. Replace the input shaft speed sensor. See «INPUT SHAFT SPEED SENSOR»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 13 .
12. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
13. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park. The input shaft speed sensor must be greater than 500 RPM for 2 seconds. Select SPECIFIC DTC. Enter DTC P0717. Has the test run and passed? If so, go to next step. If not, go to step 2 .
14. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring harness for poor connections at ISS, transaxle in-line 20-pin connector and PCM. Check for bent, backed out or damaged terminals, or for poor terminal tension. Check for chafed wiring. When diagnosing an intermittent condition, wiggle wiring harness while observing scan tool for change in value. Inspect transaxle in-line 20-pin connector for transaxle fluid. Check for Electromagnetic Interference (EMI) in ISS signal and ground circuits. EMI may be induced by a misrouted wiring harness along spark plug wires.

DTC P0719: TCC BRAKE SWITCH CIRCUIT LOW INPUT (SWITCH STUCK ON)

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Note. TCC brake switch is also known as the stoplamp switch.

The TCC brake switch indicates brake pedal status to the PCM. The TCC brake switch indicates that the brake pedal is either applied or released. The normally-closed switch supplies battery voltage to the PCM. Applying the brake pedal opens the TCC brake switch, interrupting voltage to the PCM. When the PCM receives zero volts at the TCC brake switch input, the PCM turns OFF the Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve.

If the PCM detects an open brake switch (indicating pedal applied) during a number of accelerations, then DTC P0719 sets. DTC P0719 is a type "C" DTC.

Conditions For Running DTC P0719

1. No VSS DTC P0502 or P0503.
2. DTC P0719 has not passed this ignition cycle.

Conditions For Setting DTC P0719

DTC will set under the following conditions

1. The TCC brake switch indicates continuously open (zero volts) for more than 15 minutes and the following conditions occur 8 times consecutively. The vehicle speed is less than 5 MPH. Then the vehicle speed is between 5 and 20 MPH for at least 3 seconds. Finally, the vehicle speed remains above 20 MPH for 6 seconds.

PCM performs the following if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM disregards the TCC brake switch for TCC scheduling when all of the following conditions are met: The throttle angle is greater than 6 percent. The vehicle speed is greater than 37 MPH. The throttle angle was previously greater than 12 percent while the vehicle speed was greater than 42 MPH. The TCC brake switch has not indicated OFF for more than 2 seconds this trip.
3. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
4. The PCM stores DTC P0719 in PCM history.

Conditions For Clearing DTC P0719

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 5 - This step isolates the fault between the TCC brake switch and the harness.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, observe the TCC brake switch parameter. Does the scan tool display CLOSED? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
3. Remove the fuse from the ignition "1" voltage circuit. Inspect the fuse for an open. Replace the fuse if necessary. Was the fuse open? If so, go to next step. If not, go to step 5 . NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
4. Test the ignition "1" voltage circuit (CKT 339) of the TCC brake switch for a short to ground between the fuse block and the brake switch. Did you find and correct the condition? If so, go to step 10 . NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
5. Disconnect the TCC brake switch 4-pin connector. Connect a fused jumper wire from terminal "C" to terminal "D" of the TCC brake switch connector. Turn ignition ON, engine OFF. With a scan tool, observe the TCC brake switch parameter. Does the scan tool display CLOSED? If so, go to step 8 . If not, go to next step.
6. Test the ignition "1" voltage circuit (CKT 339) of the TCC brake switch for an open between the fuse block and the brake switch. Did you find and correct the condition? If so, go to step 10 . If not, go to next step.
7. Test the signal circuit (CKT 420) of the TCC brake switch for an open between the PCM and the brake switch. Did you find and correct the condition? If so, go to step 10 . If not, go to step 9 .
8. Replace the TCC brake switch (stoplamp switch). See «STOPLAMP SWITCH»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the repair? If so, go to step 10 .
9. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the repair? If so, go to next step.
10. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Turn ignition ON, engine OFF. The TCC brake switch must be closed (pedal released) for more than 2 seconds. Select SPECIFIC DTC. Enter DTC P0719. Has the test run and passed? If so, go to next step. If not, go to Step 2 .
11. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value. Check TCC brake switch for proper adjustment. Check PCM calibration for a current update.

DTC P0724: TCC BRAKE SWITCH CIRCUIT HIGH INPUT (SWITCH STUCK OFF)

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Note. TCC brake switch is also known as the stoplamp switch.

The TCC brake switch indicates brake pedal status to the PCM. The TCC brake switch indicates that the brake pedal is either applied or released. The normally-closed switch supplies battery voltage to the PCM. Applying the brake pedal opens the TCC brake switch, interrupting voltage to the PCM. When the PCM receives zero volts at the TCC brake switch input, the PCM turns OFF the torque converter clutch pulse width modulation (TCC PWM) solenoid valve.

If the PCM detects a closed TCC brake switch (indicating pedal released) during a number of decelerations, then DTC P0724 sets. DTC P0724 is a type "C" DTC.

Conditions For Running DTC P0724

DTC will run under the following conditions

1. No VSS DTC P0502 or P0503.

Conditions For Setting DTC P0724

DTC will set under the following conditions

1. The TCC brake switch indicates continuously CLOSED (12 volts) while the following conditions occur 8 times consecutively: The vehicle speed is greater than 20 MPH for 6 seconds. Then the vehicle speed is between 5-20 MPH for 3 seconds. Finally, the vehicle speed is less than 5 MPH.

PCM performs the following if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
3. The PCM stores DTC P0724 in PCM history.

Conditions For Clearing DTC P0724

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - If the scan tool indicates CLOSED in Step 2, and OPEN when the TCC brake switch is disconnected, the switch is stuck closed.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, observe the TCC brake switch parameter. Apply the brake pedal. Does the scan tool display OPEN? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
3. Turn ignition OFF. Disconnect the TCC brake switch 4-pin connector. Turn ignition ON, engine OFF. With a scan tool, observe the TCC brake switch parameter. Does the scan tool display OPEN? If so, go to step 5 . If not, go to next step.
4. Test the signal circuit (CKT 420) of the TCC brake switch for a short to power between the PCM and the TCC brake switch. Did you find and correct the condition? If so, go to step 7 . If not, go to step 6 .
5. Replace the TCC brake switch (stoplamp switch). See «STOPLAMP SWITCH»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 7 .
6. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
7. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Turn ignition ON, engine OFF. Apply the brake pedal. The TCC brake switch must be open for more than 2 seconds. Select SPECIFIC DTC. Enter DTC P0724. Has the test run and passed? If so, go to next step. If not, go to step 2 .
8. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value. Check TCC brake switch for proper adjustment. Check PCM calibration for a current update.

DTC P0730: INCORRECT GEAR RATIO

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The PCM calculates the gear ratio based on data from the Input Shaft Speed (ISS) sensor and the Vehicle Speed Sensor (VSS). The PCM compares the known transaxle gear ratio to a calculated ratio for each gear range selected. The VSS output is translated to RPM and MPH by the PCM for various uses.

If the PCM detects an incorrect gear ratio because of excessive slip within the transaxle, then DTC P0730 sets. DTC P0730 is a type "C" DTC.

Conditions For Running DTC P0730

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
5. The transmission fluid temperature is greater than 68°F (20°C).
6. The throttle angle is greater than 14 percent.
7. The vehicle speed is greater than 5 MPH.
8. The engine torque is 50-300 ft. lbs. (70-407 N.m).
9. The time since the last gear range change is greater than 6 seconds.

Conditions For Setting DTC P0730

DTC sets when one of the following conditions occurs for 7 seconds

1. Gear ratio is more than 2.97:1.
2. Gear ratio is 2.43:1 to 2.87:1.
3. Gear ratio is 1.62:1 to 2.33:1.
4. Gear ratio is 1.05:1 to 1.52:1.
5. Gear ratio is .75:1 to .95:1.
6. The gear ratio is less than .65:1.

PCM performs the following actions if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P0730 in PCM history.

Conditions For Clearing DTC P0730

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - This step tests for low fluid level, which may cause slipping and result in an undefined gear ratio.
2. 3 - This step verifies that the correct gear ratios occur for commanded gears.
3. 5 - This step tests for low line pressure.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Visually inspect the transaxle cooling system for fluid leaks. Did you find the condition? If so, go to step 7 . If not, go to next step.
3. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
4. Install a scan tool. Start the engine. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. Using the scan tool, select CURRENT GEAR and GEAR RATIO. Drive the vehicle in gear ranges 1, 2, 3, 4 and Reverse with the throttle angle greater than 14 percent. Record the gear ratio for each gear. Was each gear ratio within the specified ranges? Reverse: 2.33:1 to 2.43:1 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
5. Perform the line pressure check. See «HYDRAULIC PRESSURE TESTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__hydraulic-pressure-tests) under PERFORMANCE TESTS. Did you find the condition? If so, go to step 8 . If not, go to next step.
6. Inspect for clutch slippage. See «SYMPTOM DIAGNOSIS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__symptom-diagnosis) under TROUBLE SHOOTING. Did you complete the repair? If so, go to step 8 .
7. Repair the transaxle cooling system as necessary. Did you complete the repair? If so, go to next step.
8. Change the transmission fluid and filter. See «DRAINING & REFILLING»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__draining-refilling) under LUBRICATION in SERVICING - CENTURY & REGAL article. Using the scan tool, perform the CLEAR TAPS function. Did you complete the above procedure? If so, go to next step. NOTE: The CLEAR TAPS function will clear all adapt cells. This may affect transaxle performance. The PCM will update the transaxle adapt cell values as the vehicle is driven.
9. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Start the engine and let the engine run until the transmission fluid temperature is greater than 68°F (20°C). Drive the vehicle with the throttle angle greater than 14 percent and the vehicle speed greater than 5 MPH. Ensure that any one of the gear ratio values are obtained for at least 7 seconds. Reverse: 2.33:1 to 2.43:1 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Select SPECIFIC DTC. Enter DTC P0730. Has the test run and passed? If so, go to next step. If not, go to step 2 .
10. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

Inspect for the following items

1. Inspect for intermittent conditions in the ISS circuit.
2. Inspect for intermittent conditions in the OSS circuit.
3. Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in O/D.
4. Ensure that the current calibration is correct for the final drive ratio.
5. Ensure the wiring harness is not stretched too tightly or other components are pressing on the A/T inline 20-pin connector body. Also inspect for proper clearance to any other components and wiring.

DTC P0741: TCC SYSTEM STUCK OFF

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The PCM controls the Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve. The solenoid controls the hydraulic fluid for TCC apply and release. When the TCC is fully applied, the engine is coupled directly to the transaxle through the TCC.

The TCC used is an Electronically Controlled Capacity Clutch (ECCC). The PCM will normally allow a small amount of slip to occur with the ECCC. When the TCC is engaged, TCC slip speed is maintained at approximately 20 to 50 RPM.

If the PCM detects high torque converter slip when the TCC is commanded ON, then DTC P0741 sets. DTC P0741 is a type "B" DTC.

Conditions For Running DTC P0741

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. No TCC stuck on DTC P0742.
5. No TCC PWM solenoid valve DTC P1860.
6. No TCC release switch DTC P1887.
7. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
8. The time since the last gear range change is greater than 6 seconds.
9. The transmission fluid temperature is 68-266°F (20-130°C).
10. The throttle angle is 4-35 percent.
11. The TCC PWM solenoid valve is commanded ON for more than .5 seconds.

Conditions For Setting DTC P0741

DTC will set if following conditions exist for 2 times during the same ignition cycle

1. The TCC duty cycle is greater than 50 percent for 7 seconds.
2. The TCC slip speed is greater than 180 RPM for 7 seconds.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM inhibits TCC.
3. The PCM inhibits 4th gear if the transaxle is in Hot Mode.
4. The PCM freezes shift adapts.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0741 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P0741

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step verifies that the TCC engages when commanded ON by the scan tool.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Drive vehicle at 45 mph. With the scan tool, command the TCC PWM solenoid valve ON. Monitor TCC slip speed. Does the scan tool indicate the TCC slip speed is within -50 RPM to +180 RPM? If so, go to «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
4. Inspect the following components: The cooling system for plugging. The TCC control valve for sticking. The TCC regulator apply valve for sticking. The TCC PWM solenoid valve for sticking and the "O" ring seal for leaks. The pressure regulator valve. The TCC blowoff valve or spring for damage or improper seating. The TCC signal orifice in the spacer plate for plugging. The number one check ball missing or leaking. The spacer plate gaskets for tearing or leaking. The turbine shaft seals for leaks. The TCC. Repair or replace component as necessary. When the repair is complete, go to next step.
5. Select DTC. Select Clear Info. Operate the vehicle under the following conditions: Drive the vehicle in D3 or D4 until the TCC is engaged. The transmission fluid temperature is 68-266°F (20-130°C). The TP angle must be 4-35 percent. The time since the last range change is 6 seconds. The TCC is commanded ON at greater than 50 percent duty cycle. TCC slip speed must be less than 50 RPM for at least 4 seconds. Select specific DTC. Enter DTC P0741. If the test has run and passed, go to next step. If not passed, go to step 2 .
6. With a scan tool, observe the stored information, capture info and DTC info. If there are any DTCs that are displayed by the scan tool and have not been diagnosed, go to the appropriate SELF-DIAGNOSTICS article under ENGINE PERFORMANCE. If there are no more codes, the system is OK.

1. Prior to replacing the torque converter refer to «TORQUE CONVERTER REPLACEMENT GUIDE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under TROUBLE SHOOTING.
2. Residue or contamination may cause valves to stick intermittently.

DTC P0742: TCC SYSTEM STUCK ON

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The TCC release switch is part of the Transmission Fluid Pressure (TFP) manual valve position switch. The TFP manual valve position switch is mounted to the transaxle valve body.

The TCC release switch is a normally-closed switch. When the TCC is released, TCC release fluid pressure opens the TCC release switch, which opens the TCC release pressure circuit. When the voltage on the circuit is high (switch open), the PCM recognizes that the TCC is no longer engaged.

If the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type "B" DTC.

Conditions For Running DTC P0742

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No TCC PWM solenoid valve DTC P1860.
3. No TCC release switch DTC P1887.
4. The engine speed is greater than 500 RPM and not in fuel shut-off.
5. The engine torque is 70-200 ft. lbs. (95-270 N.m).
6. The throttle angle is 5-45 percent.
7. The transmission fluid temperature is 50-266°F (10-130°C).
8. The time since the last gear range change is greater than 6 seconds.
9. The TCC is commanded OFF.

Conditions For Setting DTC P0742

DTC will set under the following conditions

1. The TCC release switch is closed 6 times for 4 seconds each, during one trip.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM commands the TCC ON at maximum capacity.
3. The PCM freezes shift adapts.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
5. The PCM stores DTC P0742 in PCM history.

Conditions For Clearing DTC P0742

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - A YES answer indicates that the TCC is functioning properly.
2. 4 - With the 20-pin connector disconnected, the PCM should interpret the open circuit as TCC release pressure present.
3. 5 - An open condition in the TCC release circuit or switch would set DTC P1887. Open circuits are not diagnosed in DTC P0742.
4. 8 - This step tests for a mechanical or hydraulic condition that would cause the TCC to be stuck ON.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. The "Clear Info" function will erase the data. Record the DTC freeze frame and failure records. Clear the DTCs. Start the engine. With a scan tool, observe the TCC release pressure status. Does the scan tool indicate YES for TCC release pressure? If so, go to next step. If not, go to step 5 .
3. Drive the vehicle above 45 mph in D3 or D4, with a TP angle of 5-45%. With the scan tool, command the TCC PWM solenoid valve ON and observe TCC Release Pressure. With the scan tool, command the TCC PWM solenoid valve OFF and observe TCC Release Pressure. While the TCC was commanded OFF did the TCC release pressure indicate NO at any time? If so, go to step 8 . If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
4. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Turn ignition ON, engine OFF. Observe the TCC release pressure parameter. Does the scan tool indicate YES for TCC release pressure status? If so, go to next step. If not, go to step 6 .
5. Disconnect the transmission internal wiring harness from the TFP manual valve position switch. Test the signal circuit (CKT 1804) of the TCC release switch for a short to ground between the transaxle in-line 20-pin connector and the TFP manual valve position switch. Did you find the condition? If so, go to step 10 . If not, go to step 7 .
6. Test the signal circuit (CKT 657) of the TCC release switch for a short to ground between the PCM connector C2 and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 12 . If not, go to step 11 .
7. Remove the TFP manual valve position switch. Inspect the TCC release switch for the following conditions: A damaged or leaking seal. Sediment or debris. Damaged switch contacts. Stuck switch contacts. Did you find a condition? If so, go to step 9 . If not, go to next step.
8. Inspect for the following conditions: TCC control valve stuck in the apply position. TCC PWM solenoid valve stuck or exhaust restricted or faulty internal "O" ring. TCC fluid circuits leaking. See appropriate REMOVAL & INSTALLATION article. The TCC blowoff valve or spring for damage or not seating. See appropriate REMOVAL & INSTALLATION article. Turbine shaft seals for leaks. See appropriate REMOVAL & INSTALLATION article. Pump shaft seal for leaks. See appropriate REMOVAL & INSTALLATION article. Spacer plate gaskets torn/leaking. See appropriate REMOVAL & INSTALLATION article. Pressure regulator valve stuck. See appropriate REMOVAL & INSTALLATION article. Abnormally high or low line pressure. Repair or replace any malfunctioning components. Did you find and correct a condition? If so, go to step 12 . If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
9. Replace the TFP manual valve position switch. See «TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 12 .
10. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 12 .
11. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
12. In order to verify your repair, perform the following procedure: Select DTC. Select Clear Info. Drive the vehicle in a Drive range. The throttle position must be 5-45 percent. The time since the last range change must be greater than 6 seconds. The TCC must be commanded OFF. The TCC release switch must be open, indicating TCC release pressure is present, for 2 seconds. Select SPECIFIC DTC. Enter DTC P0742. Has the test run and passed? If so, go to next step. If not, go to step 2 .
13. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The customer may notice an engine stalling condition.

If the scan tool indicated TCC release pressure was present in step 2 and a mechanical or hydraulic condition was not found in step 9 , an intermittent short to ground condition may exist in the TCC release switch signal circuit. See INTERMITTENT CONDITIONS in the appropriate ENGINE PERFORMANCE article.

DO NOT replace the torque converter for this condition.

DTC P0748: PRESSURE CONTROL SOLENOID ELECTRICAL PROBLEM

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The Pressure Control (PC) solenoid valve is located in the valve body. The PC solenoid valve controls line pressure based on current flow through its windings. The PCM determines desired line pressure based on throttle position and other inputs. The PCM then varies the duty cycle on the high side of the PC solenoid valve to control current flow to the solenoid. Current is controlled from about .02 amp for maximum line pressure to 1.1 amps for minimum line pressure. The PCM monitors the actual current to the solenoid.

If the PCM detects a commanded current draw that differs from the actual current draw by more than a calibrated value, then DTC P0748 sets. DTC P0748 is a type "C" DTC.

Conditions For Running DTC P0748

DTC will run under the following conditions

1. The PC solenoid valve is enabled.
2. The system voltage is greater than 11 volts at a low temperature of -40°F (-40°C) or greater than 13 volts at a high temperature of 304°F (151°C).

Conditions For Setting DTC P0748

DTC will set under the following conditions

1. DTC P0748 sets when the duty cycle is outside the range of .5-95 percent for .2 seconds.

PCM performs the following if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM enters PC solenoid valve diagnostic retest mode. The retest mode conducts the following diagnostic routine: The PCM de-energizes the PC solenoid valve, resulting in maximum line pressure. After being de-energized for 2 seconds, the PCM commands the PC solenoid valve on at .1 amp for the retest period of 5 seconds. If no circuit faults are detected during the 5-second retest period, then the PC solenoid valve is returned to normal operation and DTC P0748 diagnostic is passed. If a circuit fault is detected 3 times during normal operation, then the PCM de-energizes the PC solenoid valve for the remainder of that ignition cycle. If a circuit fault is detected during the 5-second retest period, then the PCM de-energizes the PC solenoid valve for 2 seconds before re-entering the retest mode. If a circuit fault is detected 5 times without returning to normal operation, then the PC solenoid valve is de-energized for the remainder of that ignition cycle.
3. The PCM freezes shift adapts.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P0748 in PCM history.

Conditions For Clearing DTC P0748

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - This step verifies that the fault is present.
2. 3 - This step tests the transaxle wiring harness and the PC solenoid valve for correct resistance.
3. 9 - This step begins diagnosis of the engine side of the circuit.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Start the engine. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, command several values of solenoid reference current from .1 amp through 1.1 amp and observe the scan tool display. Does the PC SOL. ACTUAL CURRENT reading differ from the PC SOL. REF. CURRENT reading by no more than .16 amp? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Connect the Jumper Harness (J 44152) to the transaxle side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a DMM from terminal "C" to terminal "D" of the jumper harness. Measure the resistance between terminals "C" and "D". Does the resistance measure within 3-7 ohms? If so, go to step 7 . If not, go to next step.
4. Is the resistance greater than 7 ohms? If so, go to next step. If not, go to step 6 .
5. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the transaxle in-line 20-pin connector and the PC solenoid valve. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the transaxle in-line 20-pin connector and the PC solenoid valve. Did you find the condition? If so, go to step 15 . If not, go to step 14 .
6. Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for a short together between the transaxle in-line 20-pin connector and the PC solenoid valve. Did you find the condition? If so, go to step 15 . If not, go to step 14 .
7. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to the transaxle case between the transaxle in-line 20-pin connector and the PC solenoid valve. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to other power and ground circuits in the transaxle harness. Test from terminal "C" to all other terminals in the transaxle in-line 20-pin connector. Did you find the condition? If so, go to step 15 . If not, go to next step.
8. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to the transaxle case between the transaxle in-line 20-pin connector and the PC solenoid valve. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to other power and ground circuits in the transaxle harness. Test from terminal "D" to all other terminals in the transaxle in-line 20-pin connector. Did you find the condition? If so, go to step 15 . If not, go to next step.
9. Disconnect the jumper harness from the transaxle side of the 20-pin connector. Reconnect the 20-pin connector. Disconnect the PCM connector C2. Using the DMM, measure the resistance of the PC solenoid circuit between the PCM harness connector C2 terminals No. 45 and 46. Does the resistance measure within 3-7 ohms? If so, go to step 13 . If not, go to next step.
10. Does the resistance measure greater than 7 ohms? If so, go to next step. If not, go to step 12 .
11. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the PCM and the transaxle in-line 20-pin connector. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 17 .
12. Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for a short together between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 17 .
13. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground or short to power between the PCM and the transaxle in-line 20-pin connector. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground or short to power between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 17 . If not, go to step 16 .
14. Replace the PC solenoid valve. See «PRESSURE CONTROL SOLENOID VALVE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 17 .
15. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 17 .
16. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
17. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Start the engine. The PC solenoid valve actual current must be between .1 and 1.1 amp. Select SPECIFIC DTC. Enter DTC P0748. Has the test run and passed? If so, go to next step. If not, go to step 2 .
18. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Inspect wiring for poor connections at PCM, transaxle in-line 20-pin connector and pressure control solenoid. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

DTC P0751: 1-2 SHIFT SOLENOID PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 1-2 shift solenoid valve is supplied with fused ignition voltage. The ground path is controlled by the PCM. When the PCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the PCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.

The PCM identifies a 1-2 shift solenoid valve condition by monitoring the commanded gear versus gear ratio.

If the PCM detects a 2nd gear ratio when 1st gear is commanded and a 3rd gear ratio when 4th gear is commanded, then DTC P0751 sets. DTC P0751 is a type "B" DTC.

Conditions For Running DTC P0751

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. No 1-2 shift solenoid valve electrical DTC P0753.
5. No 2-3 shift solenoid electrical DTC P0758.
6. No TCC PWM solenoid valve DTC P1860.
7. The vehicle speed is greater than 5 MPH.
8. The throttle angle is greater than 10 percent.
9. The transmission fluid temperature is between 68°F (20°C) and 266°F (130°C).
10. The engine torque is 20-200 ft. lbs. (27-270 N.m).
11. The input shaft speed is 150-8000 RPM.
12. The output shaft speed is greater than 300 RPM.
13. The time since the last range change is greater than one second.

Conditions For Setting DTC P0751

DTC will set under the following conditions

1. Condition 1 The PCM commands 1st gear and the gear ratio indicates 2nd gear (1.52:1 to 1.62:1) for one second.
2. Condition 2 The PCM commands 4th gear and the gear ratio indicates 3rd gear (.95:1 to 1.05:1) for one second.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
5. The PCM stores DTC P0751 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P0751

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step confirms that the PCM commanded all shifts, but all the shifts did not occur.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Accelerate the vehicle in D4 range. With the scan tool, observe current (commanded) gear and gear ratio for each gear. Standard values are: 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Did the gear ratios indicate a 2-2-3-3 shift pattern? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . CAUTION: DO NOT drive the vehicle for an extended period of time because additional internal damage may occur.
4. Inspect the 1-2 shift solenoid valve/hydraulic circuit for the following conditions: The 1-2 shift solenoid mechanically stuck OFF. A stuck or binding 1-2 shift valve. Damaged seals on the shift solenoid valve. Did you find and correct the condition? If so, go to next step.
5. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 with the throttle angle at least 10 percent until the transaxle shifts to 4th gear. Ensure that the gear ratios are as specified for 1st and 4th gear. Select SPECIFIC DTC. Enter DTC P0751. Has the test run and passed? If so, go to next step. If not, go to step 2 .
6. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

If DTC P0751 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist

1. Fluid Contamination
2. Plugged Fluid Circuits
3. Restricted Fluid Circuits

DTC P0752: 1-2 SHIFT SOLENOID PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 1-2 shift solenoid valve is supplied with fused ignition voltage. The ground path is controlled by the PCM. When the PCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the PCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.

The PCM identifies a 1-2 shift solenoid valve condition by monitoring the commanded gear versus gear ratio.

If the PCM detects a 1st gear ratio when 2nd gear is commanded and a 4th gear ratio when 3rd gear is commanded, then DTC P0752 sets. DTC P0752 is a type "B" DTC.

Conditions For Running DTC P0752

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. No 1-2 shift solenoid valve electrical DTC P0753.
5. No 2-3 shift solenoid electrical DTC P0758.
6. No TCC PWM solenoid valve DTC P1860.
7. The vehicle speed is greater than 5 MPH.
8. The throttle angle is greater than 10 percent.
9. The transmission fluid temperature is between 68°F (20°C) and 266°F (130°C).
10. The engine torque is 20-200 ft. lbs. (27-270 N.m).
11. The input shaft speed is 150-8000 RPM.
12. The output shaft speed is greater than 300 RPM.
13. The time since the last range change is greater than one second.

Conditions For Setting DTC P0752

DTC will set if the following conditions both occur twice in one trip

1. Condition 1 - The PCM commands 2nd gear and the gear ratio indicates 1st gear (2.87:1 to 2.97:1) for one second.
2. Condition 2 - The PCM commands 3rd gear and the gear ratio indicates 4th gear (.65:1 to .75:1) for one second.

PCM performs the following actions if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM commands maximum line pressure.
3. The PCM inhibits TCC.
4. The PCM freezes shift adapts.
5. The PCM inhibits 3-2 downshifts when the vehicle speed is greater than 30 MPH.
6. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
7. The PCM stores DTC P0752 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P0752

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step confirms that the PCM commanded all shifts, but all the shifts did not occur.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the "Clear Info" function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Accelerate the vehicle in D4 range. With the scan tool, observe current (commanded) gear and gear ratio for each gear. Standard values are: 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Did the gear ratios indicate a 1-1-4-4 shift pattern? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . CAUTION: DO NOT drive the vehicle for an extended period of time because additional internal damage may occur.
4. Inspect the 1-2 shift solenoid valve/hydraulic circuit for the following conditions: The 1-2 shift solenoid mechanically stuck ON. A stuck or binding 1-2 shift valve. Did you find and correct the condition? If so, go to next step.
5. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 with the throttle angle at least 10 percent until the transaxle shifts to 4th gear. Ensure that the gear ratios are as specified for 2nd and 3rd gear. Select SPECIFIC DTC. Enter DTC P0752. Has the test run and passed? If so, go to next step. If not, go to step 2 .
6. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

If DTC P0752 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist

1. Fluid Contamination
2. Plugged Fluid Circuits
3. Restricted Fluid Circuits

DTC P0753: 1-2 SHIFT SOLENOID ELECTRICAL PROBLEM

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 1-2 shift solenoid valve controls transmission fluid pressure acting on the 1-2 shift valves to position the valves for the appropriate gear. The 1-2 shift solenoid valve is a normally-open exhaust valve located on the control valve body. A fused circuit supplies ignition voltage to the 1-2 shift solenoid valve. The PCM commands the solenoid ON or OFF by switching the ground path. When the 1-2 shift solenoid valve is commanded ON, the PCM senses low voltage. When the 1-2 shift solenoid valve is commanded OFF, the PCM senses high voltage.

If the PCM detects a continuous open, short to ground or short to power in the 1-2 shift solenoid valve circuit, then DTC P0753 sets. DTC P0753 is a type "B" DTC.

Conditions For Running DTC P0753

DTC will run under the following conditions

1. The system voltage is 9-18 volts.
2. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
3. The PCM has commanded the 1-2 shift solenoid valve ON and OFF.

Conditions For Setting DTC P0753

DTC will set if one of the following conditions occurs for 5 seconds

1. Condition 1 - The PCM commands the solenoid ON and voltage feedback remains high (B+).
2. Condition 2 - The PCM commands the solenoid OFF, and the voltage feedback remains low (zero volts).

PCM performs the following actions if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM inhibits 3-2 downshifts when the vehicle speed is greater than 30 MPH.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0753 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Condition For Clearing DTC P0753

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - A short to ground in the power feed circuit to the solenoid ahead of the splice would open the fuse and set DTCs for other solenoids on the same circuit. An open in the same circuit would not open the fuse, but would set the other DTCs.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Are DTCs P0758 or P1860 also set? If so, go to next step. If not, go to step 9 .
3. Inspect the fuse in the ignition "1" voltage circuit for an open. Replace the fuse if necessary. Was the fuse open? If so, go to next step. If not, go to step 7 .
4. Test the ignition "1" voltage circuit (CKT 1039) of the 1-2 shift solenoid valve for a short to ground between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
5. Disconnect the transaxle internal wiring harness from the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid valve. Test the ignition "1" voltage circuit (CKT 839) of the 1-2 shift solenoid valve for a short to ground between the transaxle in-line 20-pin connector and the solenoids. Did you find the condition? If so, go to step 17 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
6. Test the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid valve for a short to ground between the ignition "1" voltage side of each solenoid and the transaxle case. Replace any faulty solenoid. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article. Did you complete the replacement? If so, go to step 20 .
7. Test the ignition "1" voltage circuit (CKT 1039) of the 1-2 shift solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
8. Test the ignition "1" voltage circuit (CKT 839) of the 1-2 shift solenoid valve for an open between the transaxle in-line 20-pin connector and the solenoid. Did you find the condition? If so, go to step 17 . If not, see INTERMITTENT CONDITIONS in the appropriate ENGINE PERFORMANCE article.
9. Turn ignition OFF. Disconnect the transaxle in-line 20-pin harness connector (additional DTCs may set). Install the Jumper Harness (J 44152) on the engine side of the transaxle in-line 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a test lamp from terminal "A" to terminal "E" of the jumper harness. Turn ignition ON, engine OFF. With a scan tool, command the 1-2 shift solenoid valve ON and OFF three times. Does the test lamp turn ON and OFF? If so, go to step 12 . If not, go to next step.
10. Test the ignition "1" voltage circuit (CKT 1039) of the 1-2 shift solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
11. Test the control circuit (CKT 1222) of the 1-2 shift solenoid valve for an open, short to ground or short to power between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to step 19 .
12. Connect the jumper harness to the transaxle side of the transaxle in-line 20-pin connector. Using a DMM, measure the resistance of the 1-2 shift solenoid valve circuit between terminals "A" and "E" of the jumper harness. Does the resistance measure within 19-31 ohms? If so, go to next step. If not, go to step 16 .
13. Measure the resistance from terminals "A" and "E" to the transaxle case. Are both readings greater than 10 k/ohms? If so, see go to next step. If not, go to step 15 .
14. Measure the resistance from terminal A and all other terminals of the A/T inline 20-pin connector. Did you find a condition of 10 k/ohms? If so, go to step 16 . If not, go to INTERMITTENT CONDITIONS in the appropriate ENGINE PERFORMANCE article.
15. Disconnect the harness at the solenoid. Measure the resistance from each terminal of the solenoid to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to step 17 . If not, go to step 18 .
16. Disconnect the harness from the 1-2 shift solenoid valve. Measure the resistance of the solenoid. Is the resistance within 19-31 ohms? If so, go to next step. If not, go to step 18 .
17. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 20 .
18. Replace the 1-2 shift solenoid valve. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article. Did you complete the replacement? If so, go to step 20 .
19. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
20. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 until the transaxle shifts to 2nd gear and maintain speed for at least 5 seconds. Ensure that the gear ratios are as specified for 1st and 2nd gear. Select SPECIFIC DTC. Enter DTC P0753. Has the test run and passed? If so, go to next step. If not, go to step 2 .
21. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Inspect wiring for poor connections at PCM, transaxle in-line 20-pin connector and 1-2 shift solenoid. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value. Ensure scan tool commanded gear has correct solenoid status and gear ratio.

DTC P0756: 2-3 SHIFT SOLENOID PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 2-3 shift solenoid valve is supplied with fused ignition voltage. The ground path is controlled by the PCM. When the PCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the PCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.

The PCM identifies a 2-3 shift solenoid valve performance condition by monitoring the commanded gear versus the gear ratio.

If the PCM detects a 4th gear ratio when 1st gear is commanded and a 3rd gear ratio when 2nd gear is commanded, then DTC P0756 sets. DTC P0756 is a type "A" DTC.

Conditions For Running DTC P0756

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. No 1-2 shift solenoid valve electrical DTC P0753.
5. No 2-3 shift solenoid valve electrical DTC P0758.
6. No TCC PWM solenoid valve DTC P1860.
7. The transmission fluid temperature is between 68°F (20°C) and 266°F (130°C).
8. The vehicle speed is greater than 5 MPH.
9. The throttle angle is greater than 10 percent.
10. The engine torque is 60-200 ft. lbs. (81-270 N.m).
11. The input shaft speed is 150-8000 RPM.
12. The output shaft speed is greater than 300 RPM.
13. The time since the last range change is greater than one second.

Conditions For Setting DTC P0756

DTC will set if following conditions both occur twice in one trip

1. Condition 1 - The PCM commands 1st gear and the gear ratio indicates 4th gear (.65:1 to .75:1) for one second.
2. Condition 2 - The PCM commands 2nd gear and the gear ratio indicates 3rd gear (.95:1 to 1.05:1) for one second.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL.
2. The PCM commands 2nd gear.
3. The PCM commands maximum line pressure.
4. The PCM freezes shift adapts.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0756 in PCM history.

Conditions For Clearing DTC P0756

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step confirms that the PCM commanded all shifts, but all the shifts did not occur.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Accelerate the vehicle in D4 range. With the scan tool, observe current (commanded) gear and gear ratio for each gear. Standard values are: 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Did the gear ratios indicate a 4-3-3-4 shift pattern? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . CAUTION: DO NOT operate the transaxle continuously in an incorrect gear ratio. Internal transaxle component damage may occur.
4. Inspect the 2-3 shift solenoid valve/hydraulic circuit for the following conditions: The 2-3 shift solenoid mechanically stuck OFF. A stuck or binding 2-3 shift valve. Damaged seals on the shift solenoid valve. Did you find and correct the condition? If so, go to next step.
5. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 with the throttle angle at least 10 percent until the transaxle shifts to 2nd gear. Ensure that the gear ratios are as specified for 1st and 2nd gear. Select SPECIFIC DTC. Enter DTC P0756. Has the test run and passed? If so, go to next step. If not, go to step 2 .
6. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

It is possible to have a 2nd or 3rd gear ratio depending on the type of malfunction.

If DTC P0756 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist

1. Fluid contamination.
2. Plugged fluid circuits.
3. Restricted fluid circuits.

DTC P0757: 2-3 SHIFT SOLENOID VALVE PERFORMANCE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 2-3 shift solenoid valve is supplied with fused ignition voltage. The ground path is controlled by the PCM. When the PCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the PCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure.

The PCM identifies a 2-3 shift solenoid valve performance condition by monitoring the commanded gear versus the gear ratio.

If the PCM detects a 2nd gear ratio when 3rd gear is commanded and a 1st gear ratio when 4th gear is commanded, then DTC P0757 sets. DTC P0757 is a type "A" DTC.

Conditions For Running DTC P0757

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122 or P0123.
2. No VSS DTC P0502 or P0503.
3. No ISS sensor DTC P0716 or P0717.
4. No 1-2 shift solenoid valve electrical DTC P0753.
5. No 2-3 shift solenoid valve electrical DTC P0758.
6. No TCC PWM solenoid valve DTC P1860.
7. The system voltage is 8-18 volts.
8. The engine torque is 20-200 ft. lbs. (27-270 N.m).
9. The transmission fluid temperature is between 68°F (20°C) and 266°F (130°C).
10. The vehicle speed is greater than 5 MPH.
11. The throttle angle is greater than 10 percent.
12. The transaxle input shaft speed is 150-8000 RPM.
13. The transaxle output shaft speed is greater than 300 RPM.
14. The time since the last range change is greater than one second.

Conditions For Setting DTC P0757

DTC will set if following conditions both occur twice in one trip

1. Condition 1 - The PCM commands 3rd gear and the gear ratio indicates 2nd gear (1.52:1 to 1.62:1) for one second.
2. Condition 2 - The PCM commands 4th gear and the gear ratio indicates 1st gear (2.87:1 to 2.97:1) for one second.

PCM performs the following if DTC is set

1. The PCM illuminates the MIL.
2. The PCM commands maximum line pressure.
3. The PCM inhibits TCC.
4. The PCM commands 2nd gear.
5. The PCM freezes shift adapts.
6. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
7. The PCM stores DTC P0757 in PCM history.

Conditions For Clearing DTC P0757

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step confirms that the PCM commanded all shifts, but all the shifts did not occur.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the "Clear Info" function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Accelerate the vehicle in D4 range. With the scan tool, observe current (commanded) gear and gear ratio for each gear. Standard values are: 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Did the gear ratios indicate a 1-2-2-1 shift pattern? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . CAUTION: DO NOT drive the vehicle for an extended period of time, as additional internal damage may occur.
4. Inspect the 2-3 shift solenoid valve/hydraulic circuit for the following conditions: The 2-3 shift solenoid mechanically stuck ON. A stuck or binding 2-3 shift valve. Did you find and correct the condition? If so, go to next step.
5. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 with the throttle angle at least 10 percent until the transaxle shifts to 4th gear. Ensure that the gear ratios are as specified for 3rd and 4th gear. Select SPECIFIC DTC. Enter DTC P0757. Has the test run and passed? If so, go to next step. If not, go to step 2 .
6. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

If DTC P0757 is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist

1. Fluid contamination.
2. Plugged fluid circuits.
3. Restricted fluid circuits.

DTC P0758: 2-3 SHIFT SOLENOID ELECTRICAL PROBLEM

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The 2-3 shift solenoid valve controls transmission fluid pressure acting on the 1-2 and 2-3 shift valves to position the valves for the appropriate gear. The 2-3 shift solenoid valve is a normally-open exhaust valve located on the control valve body. A fused circuit supplies ignition voltage to the 2-3 shift solenoid valve. The PCM commands the solenoid ON or OFF by switching the ground path. When the 2-3 shift solenoid valve is commanded ON, the PCM senses low voltage. When the 2-3 shift solenoid valve is commanded OFF, the PCM senses high voltage.

If the PCM detects a continuous open, short to ground or short to power in the 2-3 shift solenoid valve circuit, then DTC P0758 sets. DTC P0758 is a type "A" DTC.

Conditions For Running DTC P0758

DTC will run under the following conditions

1. The system voltage is 9-18 volts.
2. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
3. The PCM has commanded the 2-3 shift solenoid valve ON and OFF.

Conditions For Setting DTC P0758

DTC will set when one of the following conditions is met for 5 seconds

1. Condition 1 - The PCM commands the solenoid ON and the voltage feedback remains high (B+).
2. Condition 2 - The PCM commands the solenoid OFF and the voltage feedback remains low (zero volts).

PCM performs the following actions if DTC is set

1. The PCM illuminates the MIL.
2. The PCM commands 2nd gear.
3. The PCM commands maximum line pressure.
4. The PCM inhibits TCC.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P0758 in PCM history.

Conditions For Clearing DTC P0758

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - A short to ground in the power feed circuit to the solenoid ahead of the splice would open the fuse and set DTCs for other solenoids on the same circuit. An open in the same circuit would not open the fuse but, would set the other DTCs.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Are DTCs P0753 or P1860 also set? If so, go to next step. If not, go to step 9 .
3. Inspect the fuse in the ignition "1" voltage circuit for an open. Replace the fuse if necessary. Was the fuse open? If so, go to next step. If not, go to step 7 .
4. Test the ignition "1" voltage circuit (CKT 1039) of the 2-3 shift solenoid valve for a short to ground between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
5. Disconnect the transaxle wiring harness from the 1-2 shift solenoid, the 2-3 shift solenoid and the TCC PWM solenoid. Test the ignition "1" voltage circuit (CKT 839) of the 2-3 shift solenoid valve for a short to ground between the transaxle in-line 20-pin connector and the solenoid. Did you find the condition? If so, go to step 17 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
6. Test the 1-2 shift solenoid, the 2-3 shift solenoid and the TCC PWM solenoid for a short to ground between the ignition "1" voltage side of each solenoid and the transaxle case. Replace any faulty solenoid. See appropriate shift solenoid under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 20 .
7. Test the ignition "1" voltage circuit (CKT 1039) of the 2-3 shift solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
8. Test the ignition "1" voltage circuit (CKT 839) of the 2-3 shift solenoid valve for an open between the transaxle in-line 20-pin connector and the solenoid. Did you find the condition? If so, go to step 17 . If not, see INTERMITTENT CONDITIONS in the appropriate ENGINE PERFORMANCE article.
9. Turn ignition OFF. Disconnect the transaxle 20-pin harness connector (additional DTCs may set). Install the Jumper Harness (J 44152) on the engine side of the transaxle in-line 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a test lamp from terminal "B" to terminal "E" of the jumper harness. Turn ignition ON, engine OFF. With a scan tool, command the 2-3 shift solenoid valve ON and OFF three times. Does the test lamp turn ON and OFF? If so, go to step 12 . If not, go to next step.
10. Test the ignition "1" voltage circuit (CKT 1039) of the 2-3 shift solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
11. Test the control circuit (CKT 1223) of the 2-3 shift solenoid valve for an open, a short to ground or a short to power between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to step 19 .
12. Install the jumper harness on the transaxle side of the transaxle in-line 20-pin connector. Using a DMM, measure the resistance between terminals "B" and "E" of the jumper harness. Does the resistance measure within 19-31 ohms? If so, go to next step. If not, go to step 16 .
13. Measure the resistance from terminal "B" and terminal "E" to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to next step. If not, go to step 15 .
14. Measure the resistance from terminal "B" and all other terminals of the A/T inline 20-pin connector. Did you find a condition of 10 k/ohms? If so, go to step 16 . If not, see INTERMITTENT CONDITIONS in the appropriate ENGINE PERFORMANCE article.
15. Disconnect the harness from the 2-3 shift solenoid valve. Measure the resistance from each terminal of the solenoid to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to step 17 . If not, go to step 18 .
16. Disconnect the harness from the 2-3 shift solenoid valve. Measure the resistance of the solenoid. Is the resistance within 19-31 ohms? If so, go to next step. If not, go to step 18 .
17. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. If not, go to step 20 .
18. Replace the 2-3 shift solenoid valve. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article. If not, go to step 20 .
19. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. If not, go to next step.
20. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 until the transaxle shifts into at least 3rd gear and maintain speed for at least 5 seconds. Ensure that the gear ratios are as specified. Standard values are: 1st: 2.87:1 to 2.97:1 2nd: 1.52:1 to 1.62:1 3rd: .95:1 to 1.05:1 4th: .65:1 to .75:1 Select SPECIFIC DTC. Enter DTC P0758. Has the test run and passed? If so, go to next step. If not, go to step 2 .
21. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Inspect wiring for poor connections at PCM, transaxle in-line 20-pin connector and 2-3 shift solenoid. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value. Ensure scan tool commanded gear has correct solenoid states and gear ratio.

DTC P1811: MAXIMUM ADAPT & LONG SHIFT

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The transmission fluid pressure is modified by an adaptive modifier which controls the shift execution time. This diagnostic tests the time required to accomplish the shift. If the shift takes longer than .65 seconds and the adaptive modifier cannot shorten this time, then a counter increases by one.

If the PCM detects a counter value of "2" during one trip, then DTC P1811 sets. DTC P1811 is a type "C" DTC.

Conditions For Running DTC P1811

DTC will run under the following conditions

1. The shift is adaptable.
2. The 1-2, the 2-3 or the 3-4 shift adapt cell has reached its limit.

Conditions For Setting DTC P1811

DTC will set under the following conditions

1. The 1-2, 2-3 or 3-4 shift is longer than .65 seconds, twice in one trip.

PCM performs the following if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM commands maximum line pressure.
3. The PCM freezes shift adapts.
4. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
5. The PCM stores DTC P1811 in PCM history.

Conditions For Clearing DTC P1811

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 7 - This step inspects components that may cause low line pressure.
2. 9 - This step inspects or repairs components that may cause a maximum adapt and long 1-2 upshift.
3. 11 - This step inspects or repairs components that may cause a maximum adapt and long 2-3 upshift.
4. 13 - This step inspects or repairs components that may cause a maximum adapt and long 3-4 upshift.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article.
3. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. Are any of DTCs P0121, P0122, P0123, P0218, P0502, P0503, P0711, P0712, P1121 or P1122 also set? If so, go to next step. If not, go to step 5 .
4. Diagnose the above DTCs first. Is the diagnosis and repair complete? If so, go to step 14 .
5. Use the scan tool snapshot mode to record the shift times. Drive the vehicle in D4 to obtain a 1-2, 2-3 and 3-4 upshift. Record the shift times. Did all the shift times exceed .65 seconds? If so, go to next step. If not, go to step 8 .
6. Perform the line pressure check. See «HYDRAULIC PRESSURE TESTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__hydraulic-pressure-tests) under PERFORMANCE TESTS. Is the line pressure within specifications? If so, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) . If not, go to next step.
7. Inspect the transaxle for the following conditions: Fluid level low. Oil filter and seal missing, plugged or damaged. Spacer plate and gasket damaged or misassembled. Pressure Control (PC) solenoid valve damaged or contaminated. Pressure regulator valve line-up binding or damaged. Torque signal valve line-up binding or damaged. Oil pump assembly damaged or missing components. Repair as necessary. Did you complete the repair? If so, go to step 14 .
8. Did the 1-2 shift time exceed .65 seconds? If so, go to next step. If not, go to step 10 .
9. Inspect the transaxle for the following conditions: 1-2 accumulator piston seals rolled or damaged. 1-2 accumulator piston and pin missing, binding or damaged. Forward servo assembly damaged or misassembled. Oil pump assembly damaged or missing components. Spacer plate and gaskets damaged or misassembled. Driven sprocket support seals damaged or missing. 2nd clutch piston and seal assembly binding or damaged. 2nd clutch fiber and steel plates misassembled, burned or damaged. 2nd clutch spring assembly damaged or misassembled. Forward band burned, damaged or misassembled. 1-2 support roller clutch assembly damaged or misassembled. Repair as necessary. Did you complete the repair? If so, go to step 14 .
10. Did the 2-3 shift time exceed .65 seconds. If so, go to next step. If not, go to step 12 .
11. Inspect the transaxle for the following conditions: 2-3 accumulator piston seals rolled or damaged. 2-3 accumulator piston and pin missing, binding or damaged. Oil pump assembly damaged or missing components. Spacer plate and gaskets damaged or misassembled. Driven sprocket support seals damaged or missing. 3rd clutch piston seal rolled or damaged. 3rd clutch piston damaged or misassembled. 3rd clutch fiber and steel plates misassembled, burned or damaged. 3rd clutch spring assembly damaged or misassembled. 3rd sprag clutch assembly damaged or misassembled. Repair as necessary. Did you complete the repair? If so, go to step 14 .
12. Did the 3-4 shift time exceed .65 seconds? If so, go to next step. If not, see «DIAGNOSTIC AIDS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) .
13. Inspect the transaxle for the following conditions: Oil pump assembly damaged or missing components. Spacer plate and gaskets damaged or misassembled. 3-4 accumulator piston seals rolled or damaged. 3-4 accumulator piston and pin missing, binding or damaged. 4th clutch piston seal rolled or damaged. 4th clutch piston damaged, misassembled or seized. 4th clutch fiber and steel plates misassembled, burned or damaged. 4th clutch spring assembly damaged or misassembled. Repair as necessary. Did you complete the repair? If so, go to next step.
14. Change the transmission fluid and filter. See «DRAINING & REFILLING»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__draining-refilling) under LUBRICATION in SERVICING - CENTURY & REGAL article. Using the scan tool, perform the CLEAR TAPS function. Did you complete the above procedure? If so, go to next step. NOTE: The CLEAR TAPS function will clear all adapt cells. This may affect transaxle performance. The PCM will update the transaxle adapt cell values as the vehicle is driven.
15. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4. Observe "Last Shift Time" on the scan tool. Ensure that the 1-2, 2-3 and 3-4 shift times are each less than .65 second. Was each shift time less than .65 second? If so, go to next step. If not, go to step 2 .
16. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in O/D.

Ensure that the current PCM calibration is correct for the final drive ratio.

DTC P1814: TORQUE CONVERTER OVERSTRESS

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

This diagnostic test checks for unusually high throttle angle and low vehicle speed when the transaxle is in Drive or Reverse. The primary purpose of this DTC is to record the failure record data, because this condition could damage the powertrain or create an unsafe condition.

If the PCM detects an unusually high throttle angle and low vehicle speed when the transaxle is in Drive or Reverse, then DTC P1814 sets. DTC P1814 is a type "C" DTC.

Conditions For Running DTC P1814

DTC will run under the following conditions

1. No TP sensor DTC P0121, P0122, or P0123.
2. No VSS DTC P0502 or P0503.
3. The vehicle speed is less than 7 MPH.
4. The throttle angle is 70 percent or greater.

Conditions For Setting DTC P1814

DTC will set under the following conditions

1. The TCC slip speed is greater than 2200 RPM for 12 seconds.

PCM performs the following actions if DTC is set

1. The PCM does not illuminate the MIL.
2. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as failure records.
3. The PCM stores DTC P1814 in PCM history.

Conditions For Clearing DTC P1814

DTC will clear under the following conditions

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - This step inspects the failure records for DTC P1814 occurrences.
2. 4 - This step replaces the fluid and the filter. If DTC P1814 occurs more than once in the failure records, severe TCC damage may have occurred.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the Clear Info function will erase the stored failure records from the PCM. Record the failure records. Observe the failure counter in the failure records. Clear the DTCs. Does DTC P1814 failure counter indicate more than "1"? If so, go to step 4 . If not, go to next step.
3. Inspect the transmission fluid level and color. See «CHECKING FLUID LEVEL & CONDITION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__checking-fluid-level-condition) under LUBRICATION in SERVICING - CENTURY & REGAL article. Is the inspection complete? If so, go to step 5 .
4. Replace the transmission fluid. See «DRAINING & REFILLING»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__draining-refilling) under LUBRICATION in SERVICING - CENTURY & REGAL article. Did you complete the repair? If so, go to next step.
5. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle with the gearshift lever in D4. The TCC slip must be 1500 RPM or less. The throttle angle must be 50 percent or less. The vehicle speed must be 7 MPH or less. These conditions must exist for at least 5 seconds. Select SPECIFIC DTC. Enter DTC P1814. Has the test run and passed? If so, go to next step. If not, go to step 2 . NOTE: These conditions must persist for at least 5 seconds.
6. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Ask the customer about possible overloading, exceeding the trailer towing limit or towing in O/D.

The transmission internal mode switch (IS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects a combination of IMS signals that are invalid, or a transitional state between gear selector positions, while attempting to start the vehicle, then DTC P1819 sets. DTC P1819 is a type C DTC.

Conditions For Running DTC

1. The system voltage is 9-18 volts.
2. The ignition switch is in the START position.

Conditions For Setting DTC

The PCM detects a combination of IMS signals that are invalid or indicate a transitional state between gear selector positions for .5 seconds.

Action Taken When DTC Sets

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
3. The PCM stores DTC P1819 in PCM history.

Conditions For Clearing DTC

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. 3 - HI values for all signals in both Park and Drive 4 indicates the ground circuit is OPEN.
2. 5 - With the 20-pin connector disconnected, all signals should indicate #1.
3. 7 - If one circuit affects the other, this indicates a short between the two circuits.
4. 13 - This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gear select lever in Park range, then move to Neutral range. Does each range selected match the scan tool IMS display? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Select IMS A/B/C/P on the scan tool. Place the gear select lever in Park range, then move to D4 range. Does the IMS A/B/C/P parameter indicate HI/HI/HI/HI for each range? If so, go to step 14 . If not, go to next step.
4. Inspect the transmission linkage from the gearshift lever to the manual shift shaft for proper adjustment. Adjust the linkage as necessary. See «ADJUSTMENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__adjustments) in SERVICING - CENTURY & REGAL article. Did the linkage require adjustment? If so, go to step 19 . If not, go to next step.
5. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Do the scan tool IMS A/B/C/P signals all indicate HI? If so, go to next step. If not, go to step 10 .
6. Turn OFF the ignition. Install the 20 Pin Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Turn ON the ignition, with the engine OFF. Using the DMM and the GM Terminal Test Kit (J 35616-A), measure the voltage at terminal "F" of the 20 pin jumper harness. Measure the voltage at terminal "G" of the 20 pin jumper harness. Measure the voltage at terminal "H" of the 20 pin jumper harness. Measure the voltage at terminal "J" of the 20 pin jumper harness. Does the voltage measure ignition voltage at all four terminals? If so, go to next step. If not, go to step 11 .
7. Connect a fused jumper wire from terminal "F" of the 20 pin jumper harness (signal circuit "A") to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal circuit "A" (CKT 771) is grounded, do any other signal circuits indicate LOW? If so, go to step 12 . If not, go to next step.
8. Connect a fused jumper wire from terminal "G" of the 20 pin jumper harness (signal circuit "B") to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal circuit "B" (CKT 772) is grounded, do any other signal circuits indicate LOW? If so, go to step 12 . If not, go to next step.
9. Connect a fused jumper wire from terminal "H" of the 20 pin jumper harness (signal circuit "C") to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal circuit "C" (CKT 773) is grounded, do any other signal circuits indicate LOW? If so, go to step 12 . If not, go to step 13 .
10. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate HI for a short to ground between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 19 . If not, go to step 18 .
11. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate ignition voltage for an open between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 19 . If not, go to step 18 .
12. Test the affected signal circuits of the IMS for a shorted together condition between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 19 . If not, go to step 18 .
13. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS for an open or shorted condition between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to step 16 . If not, go to step 17 .
14. Test the ground circuit (CKT 451) of the IMS for an open between the AT inline 20-pin connector and the chassis. Did you find and correct the condition? If so, go to step 19 . If not, go to next step.
15. Test the ground circuit (CKT 1050) of the IMS for an open between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to next step. If not, go to step 17 .
16. Replace the automatic transmission wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 19 .
17. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 19 .
18. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 19 .
19. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start the engine in Park range. Turn OFF the ignition. Start the engine in Neutral range. Select Specific DTC. Enter DTC P1819. Has the test run and passed? If so, go to next step. If not, go to step 2 .
20. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The transmission Internal Mode Switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects that IMS Signal A is always low, then DTC P1820 sets. DTC P1820 is a type "C" DTC.

1. No MAP DTC P0107 or P0108.
2. Engine torque is 40-300 ft. lbs. (55-407 N.m).

The IMS Signal "A" is continuously low this ignition cycle, and the following conditions occur

1. The IMS indicates Park for 2 seconds.
2. The IMS indicates transitional position D4-D3 for 60 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM commands maximum line pressure.
3. The PCM freezes transmission adaptive functions.
4. The PCM assumes D4 for shifting.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
6. The PCM stores DTC P1820 in PCM history.

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. 3 - A low value for Signal "A" indicates a short to ground in the engine harness or the PCM.
2. 5 - This step tests the internal transmission harness. A value of LOW for Signal "A" indicates the fault is in the harness. Otherwise the fault will be in the switch.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in D4. Does the scan tool IMS parameter indicate Drive 4? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS signal A indicate LOW? If so, go to next step. If not, go to step 5 .
4. Test the signal "A" circuit (CKT 771) of the IMS for a short to ground between the PCM connector C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 9 . If not, go to step 8 .
5. Turn OFF the ignition. Reconnect the AT inline 20-pin connector. Disconnect the automatic transmission wiring harness at the IMS. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS signal "A" indicate LOW? If so, go to next step. If not, go to step 7 .
6. Replace the automatic transmission wiring harness. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
7. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
8. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
9. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park for 10 seconds. Select IMS A/B/C/P on the scan tool. Move the gearshift lever from Park to D4. Ensure that IMS signal "A" changes from LOW to HI. Select Specific DTC. Enter DTC P1820. Has the test run and passed? If so, go to next step. If not, go to step 2 .
10. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The transmission internal mode switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects that IMS Signal "B" is always high, then DTC P1822 sets. DTC P1822 is a type "C" DTC.

1. No MAP DTC P0107 or P0108.
2. Engine torque is 40-300 ft. lbs. (55-407 N.m).

The IMS Signal B is continuously high this ignition cycle, and the following conditions occur

1. The IMS indicates Park for 2 seconds.
2. The IMS indicates transitional position D2-D1 for 60 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM commands maximum line pressure.
3. The PCM freezes transmission adaptive functions.
4. The PCM assumes D4 for shifting.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
6. The PCM stores DTC P1822 in PCM history.

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The number below refers to the step number on the diagnostic table.

1. 3 - This step tests the integrity of the engine harness and PCM by checking for the Signal "B" state change from HI to LOW. A LOW signal indicates the fault is either in the internal transmission harness or the switch. A HI signal indicates the fault is either in the engine harness or the PCM.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in D4. Does the scan tool IMS parameter indicate Drive 4? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Install the 20 Pin Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Using the GM Terminal Test Kit (J 35616-A), connect a fused jumper wire from terminal G of the 20 pin jumper harness to a good ground. Refer to Automatic Transmission Inline 20-pin Connector End View. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS signal B indicate LOW? If so, go to step 5 . If not, go to next step.
4. Test the signal "B" circuit (CKT 772) of the IMS for an open between the PCM connector C1 and the AT inline 20-pin connector. Did you find and correct a condition? If so, go to step 9 . If not, go to step 8 .
5. Test the signal "B" circuit (CKT 772) of the IMS for an open between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to next step. If not, go to step 7 .
6. Replace the automatic transmission wiring harness. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
7. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
8. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
9. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park for 10 seconds. Select IMS A/B/C/P on the scan tool. Move the gearshift lever from Park to D4. Ensure that IMS signal "B" changes from HI to LOW. Select Specific DTC. Enter DTC P1822. Has the test run and passed? If so, go to next step. If not go to step 2 .
10. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The transmission Internal Mode Switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects that IMS Signal "P" is always low, then DTC P1823 sets. DTC P1823 is a type "C" DTC.

1. No MAP DTC P0107 or P0108.
2. Engine torque is 40-300 ft. lbs. (55-407 N.m).

The IMS Signal P is continuously low this ignition cycle, and the following conditions occur

1. The IMS indicates Park for 2 seconds.
2. The IMS indicates transitional position N-D4 for 60 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM commands maximum line pressure.
3. The PCM freezes transmission adaptive functions.
4. The PCM assumes D4 for shifting.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
6. The PCM stores DTC P1823 in PCM history.

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. 3 - A LOW signal indicates a short to ground in the vehicle harness or the PCM.
2. 5 - This step tests the internal transmission harness without the IMS connected.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in D4. Does the scan tool IMS parameter indicate Drive 4? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS signal "P" indicate LOW? If so, go to next step. If not, go to step 5 .
4. Test the signal "P" circuit (CKT 776) of the IMS for a short to ground between the PCM connector C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 9 . If not, go to step 8 .
5. Turn OFF the ignition. Reconnect the AT inline 20-pin connector. Disconnect the automatic transmission wiring harness at the IMS. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS signal "P" indicate LOW? If so, go to next step. If not, go to step 7 .
6. Replace the automatic transmission wiring harness. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
7. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
8. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
9. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park for 10 seconds. Select IMS A/B/C/P on the scan tool. Move the gearshift lever from Park to D4. Ensure that IMS signal "P" changes from LOW to HI. Select Specific DTC. Enter DTC P1823. Has the test run and passed? If so, go to next step. If not, go to step 2 .
10. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The transmission internal mode switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects an invalid transmission range with the engine running, then DTC P1825 sets. DTC P1825 is a type "C" DTC.

The engine speed is at least 500 RPM for 5 seconds and not in fuel shut off.

The PCM detects an invalid combination of IMS signals for .5 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM commands maximum line pressure.
3. The PCM freezes transmission adaptive functions.
4. The PCM assumes D4 for shifting.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
6. The PCM stores DTC P1825 in PCM history.

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The numbers below refer to the step numbers on the diagnostic table.

1. 3 - HI values for all signals in all ranges indicates the ground circuit is OPEN.
2. 4 - With the 20-pin connector disconnected, all signals should indicate HI.
3. 6 - If one circuit affects the other, this indicates a short between the two circuits.
4. 13 - This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does each range selected match the scan tool IMS display? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Select IMS A/B/C/P on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does the IMS A/B/C/P display HI/HI/HI/HI for each range? If so, go to step 13 . If not go to next step.
4. Turn OFF the ignition. Disconnect the AT inline 20-pin connector, additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Do the scan tool IMS A/B/C/P signals all indicate HI? If so, go to next step. If not, go to step 9 .
5. Turn OFF the ignition. Install the 20 Pin Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Turn ON the ignition, with the engine OFF. Using the DMM and the GM Terminal Test Kit (J 35616-A), measure the voltage at terminal "F" of the 20 pin jumper harness. Refer to Automatic Transmission Inline 20-pin Connector End View. Measure the voltage at terminal "G" of the 20 pin jumper harness. Measure the voltage at terminal "H" of the 20 pin jumper harness. Measure the voltage at terminal "J" of the 20 pin jumper harness. Does the voltage measure ignition voltage at all four terminals? If so, go to next step. If not, go to step 10 .
6. Connect a fused jumper wire from terminal "F" of the 20 pin jumper harness signal "A" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "A" circuit (CKT 771) is grounded, do any other signal circuits indicate LOW? If so, go to step 11 . If not, go to next step.
7. Connect a fused jumper wire from terminal "G" of the 20 pin jumper harness signal "B" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "B" circuit (CKT 772) is grounded, do any other signal circuits indicate LOW? If so, go to step 11 . If not, go to next step.
8. Connect a fused jumper wire from terminal "H" of the 20 pin jumper harness signal "C" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "C" circuit (CKT 773) is grounded, do any other signal circuits indicate LOW? If so, go to step 11 . If not, go to step 12 .
9. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate HI for a short to ground between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 18 . If not, go to step 17 .
10. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate ignition voltage for an open between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 18 . If not, go to step 17 .
11. Test the affected signal circuits of the IMS for a shorted together condition between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step 18 . If not, go to step 17 .
12. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS for an open or shorted condition between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to step 15 . If not, go to step 16 .
13. Test the ground circuit (CKT 451) of the IMS for an open between the AT inline 20-pin connector and the ground connection to the chassis. Did you find and correct the condition? If so, go to step 18 . If not, go to next step.
14. Test the ground circuit (CKT 1050) of the IMS for an open between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to next step. If not, go to step 16 .
15. Replace the automatic transmission wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 18 .
16. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 18 .
17. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
18. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park for 10 seconds. Observe IMS on the scan tool. The IMS must indicate a valid range for 5 seconds. Select Specific DTC. Enter DTC P1825. Has the test run and passed? If so, go to next step. If not, go to step 2 .
19. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

The transmission Internal Mode Switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P - Parity.

If the PCM detects that IMS Signal "C" is high while the vehicle is being driven in a forward gear, then DTC P1826 sets. DTC P1826 is a type "C" DTC.

1. No VSS DTCs P0502 or P0503.
2. Vehicle speed is 14 km/h (10 mph) or greater.
3. Engine torque is 20 ft. lbs. (27 N.m) or greater.
4. DTC P1826 has not passed this key cycle.

The PCM detects IMS Signal "C" is high, while the gear ratio indicates first, second, third or fourth gear for 60 seconds.

1. The PCM does not illuminate the malfunction indicator lamp (MIL).
2. The PCM commands maximum line pressure.
3. The PCM freezes transmission adaptive functions.
4. The PCM assumes D4 for shifting.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as Failure Records.
6. The PCM stores DTC P1826 in PCM history.

1. A scan tool can clear the DTC.
2. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
3. The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

The number below refers to the step number on the diagnostic table.

1. 3 - This step tests the integrity of the engine harness and PCM by checking for the Signal "C" state change from HI to LOW. A LOW signal indicates the fault is either in the internal transmission harness or the switch. A HI signal indicates the fault is either in the engine harness or the PCM.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ON the ignition with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in D4. Does the scan tool IMS parameter indicate Drive 4? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step. NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
3. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Install the 20 Pin Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Using the GM Terminal Test Kit J 35616-A, connect a fused jumper wire from terminal "H" of the 20 pin jumper harness to a good ground. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Does IMS Signal "C" indicate LOW? If so, go to step 5 . If not, go to next step.
4. Test the signal "C" circuit (CKT 773) of the IMS for an open between the PCM connector C1 and the AT inline 20-pin connector. Did you find and correct a condition? If so, go to step 9 . If not, go to step 8 .
5. Test the signal "C" circuit (CKT 773) of the IMS for an open between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to next step. If not, go to step 7 .
6. Replace the automatic transmission wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
7. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 9 .
8. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
9. Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Start and idle the engine in Park for 10 seconds. Observe IMS A/B/C/P on the scan tool. Move the gearshift lever to D1, D2, D3 and D4 positions. Ensure that IMS Signal "C" indicates LOW for each range. Operate the vehicle within the "Conditions for Running the DTC" as specified in the supporting text. Select Specific DTC. Enter DTC P1826. Has the test run and passed? If so, go to next step. If not, go to step 2 .
10. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

DTC P1860: TCC PULSE WIDTH MODULATED SOLENOID ELECTRICAL PROBLEM

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

Ignition voltage is provided to the Torque Converter Clutch Pulse Width Modulation (TCC PWM) solenoid valve. The PCM controls the solenoid with a negative duty cycle to control application and release of TCC. When the solenoid is commanded OFF, PCM senses high voltage. When the solenoid is commanded ON, PCM senses low voltage.

DTC P1860 sets if PCM detects a voltage that is outside of calibration limits. DTC P1860 is a type "B" DTC.

Conditions For Running DTC P1860

DTC will run under the following conditions

1. Engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.

Conditions For Setting DTC P1860

DTC sets when one of the following conditions exists for at least 5 seconds

1. PCM commands solenoid to greater than 90 percent duty cycle and voltage feedback remains high (B+).
2. PCM commands solenoid to less than 10 percent duty cycle and voltage feedback remains low (zero volts).

PCM performs the following if DTC is set

1. PCM illuminates MIL during the second consecutive trip in which conditions for setting DTC are met.
2. PCM inhibits TCC.
3. PCM inhibits 4th gear if transaxle is in hot mode.
4. PCM freezes shift adapts.
5. PCM records operating conditions when the conditions for setting DTC are met. PCM stores this information as freeze frame and failure records.
6. PCM stores DTC P1860 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P1860

DTC will clear under the following conditions

1. PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear MIL/DTC.
3. PCM clears the DTC from PCM history if vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. PCM cancels the DTC default actions when ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - A short to ground in the power feed circuit to the solenoid ahead of the splice would open the fuse and set DTCs for other solenoids on the same circuit. An open in the same circuit would not open the fuse, but would set the other DTCs.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Are DTCs P0753 or P0758 also set? If so, go to next step. If not, go to step 9 .
3. Inspect the fuse in the ignition "1" voltage circuit for an open. Replace the fuse if necessary. Was the fuse open? If so, go to next step. If not, go to step 7 .
4. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for a short to ground between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
5. Disconnect the transaxle wiring harness from the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid. Test the ignition "1" voltage circuit (CKT 839) of the TCC PWM solenoid valve for a short to ground between the transaxle in-line 20-pin connector and the solenoids. Did you find the condition? If so, go to step 17 . If not, go to next step. NOTE: The condition that affects this circuit may exist in other connecting branches of the circuit.
6. Test the 1-2 shift solenoid valve, the 2-3 shift solenoid valve and the TCC PWM solenoid valve for a short to ground between the ignition "1" voltage side of each solenoid and the transaxle case. Replace any faulty solenoid. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article. Did you complete the replacement? If so, go to step 20 .
7. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
8. Test the ignition "1" voltage circuit (CKT 839) of the TCC PWM solenoid valve for an open between the transaxle in-line 20-pin connector and the solenoid. Did you find the condition? If so, go to step 17 . If not, see INTERMITTENT CONDITIONS within the appropriate ENGINE PERFORMANCE article.
9. Turn ignition OFF. Disconnect the transaxle 20-pin harness connector (additional DTCs may set). Install the Jumper Harness (J 44152) on the engine side of the transaxle in-line 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a test lamp from terminal "T" to terminal "E" of the jumper harness. Turn ignition ON, engine OFF. With a scan tool, command the TCC PWM solenoid valve ON and OFF three times. Does the test lamp turn ON and OFF? If so, go to step 12 . If not, go to next step.
10. Test the ignition "1" voltage circuit (CKT 1039) of the TCC PWM solenoid valve for an open between the fuse block and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to next step.
11. Test the control circuit (CKT 418) of the TCC PWM solenoid valve for an open, a short to ground or a short to power between the PCM and the transaxle in-line 20-pin connector. Did you find and correct the condition? If so, go to step 20 . If not, go to step 19 .
12. Connect the jumper harness to the transaxle side of the transaxle in-line 20-pin connector. Using a DMM, measure the resistance between terminals "T" and "E" of the jumper harness. Does the resistance measure within 10-15 ohms? If so, go to next step. If not, go to step 16 .
13. Measure the resistance from terminals "T" and "E" to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to next step. If not, go to step 15 .
14. Measure the resistance from terminal T and all other terminals of the A/T inline 20-pin connector. Did you find a condition of 10 k/ohms? If so, go to step 16 . If not, see INTERMITTENT CONDITIONS within the appropriate ENGINE PERFORMANCE article.
15. Disconnect the harness at the solenoid. Measure the resistance from each terminal of the solenoid to the transaxle case. Are both readings greater than 10 k/ohms? If so, go to step 17 . If not, go to step 18 .
16. Disconnect the harness from the TCC PWM solenoid valve. Measure the resistance of the solenoid. Is the resistance within 10-15 ohms? If so, go to next step. If not, go to step 18 .
17. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 20 .
18. Replace the TCC PWM solenoid valve. See «TORQUE CONVERTER CLUTCH PULSE WIDTH MODULATION SOLENOID»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 20 .
19. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
20. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D3 or D4 until the TCC is commanded on. The TCC duty cycle must be greater than 60 percent for at least 5 seconds continuously. Release the throttle to command less than 10 percent duty cycle. Select SPECIFIC DTC. Enter DTC P1860. Has the test run and passed? If so, go to next step. If not, go to step 2 .
21. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Inspect wiring for poor connections at PCM and transaxle. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value. Ensure transaxle fluid is at proper level.

DTC P1887: TORQUE CONVERTER CLUTCH RELEASE SWITCH CIRCUIT MALFUNCTION

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The TCC release switch is part of the Transmission Fluid Pressure (TFP) manual valve position switch. The TFP manual valve position switch is mounted to the transaxle valve body. The TCC release switch is normally closed.

The switch signals the PCM that the TCC is released. This is accomplished by torque converter release fluid pressure acting on the switch contact which opens the circuit. When the circuit voltage is high, the PCM recognizes that the TCC is no longer engaged.

If the PCM determines that the TCC release switch is open (indicating that the TCC is not applied) and the TCC slip speed indicates that the TCC is applied, then DTC P1887 sets. DTC P1887 is a type "B" DTC.

Conditions For Running DTC P1887

DTC will run under the following conditions

1. No ISS sensor DTC P0716 or P0717.
2. No TCC PWM solenoid valve DTC P0741, P0742 or P1860.
3. The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut-off.
4. The TCC is commanded ON.
5. The TCC slip speed is -20 to 60 RPM.
6. The engine torque is 30-300 ft. lbs. (41-407 N.m).

Conditions For Setting DTC P1887

DTC will set when the following condition occurs twice in a single trip

1. The TCC release pressure switch is open (indicating release pressure present) for 6 seconds continuous.

PCM performs the following actions if DTC is set

1. The PCM illuminates the MIL during the second consecutive trip in which the "Conditions for Setting the DTC" are met.
2. The PCM inhibits TCC.
3. The PCM inhibits 4th gear if the transaxle is in hot mode.
4. The PCM freezes shift adapts.
5. The PCM records the operating conditions when the "Conditions for Setting the DTC" are met. The PCM stores this information as freeze frame and failure records.
6. The PCM stores DTC P1887 in PCM history during the second consecutive trip in which the "Conditions for Setting the DTC" are met.

Conditions For Clearing DTC P1887

DTC will clear under the following conditions

1. The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
2. A scan tool can clear the MIL/DTC.
3. The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
4. The PCM cancels the DTC default actions when the ignition is OFF long enough to power down the PCM.

The numbers listed below refer to step numbers in the diagnostic procedure

1. 3 - This step tests the PCM's ability to recognize a grounded circuit.
2. 4 - A short to ground in this circuit would set DTC P0742.
3. 5 - A short to ground in this circuit would set DTC P0742.

1. Did you perform the diagnostic system check? If so, go to next step. If not, see «DIAGNOSTIC SYSTEM CHECK»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under SELF-DIAGNOSTIC SYSTEM.
2. Install a scan tool. Turn ignition ON, engine OFF. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records for reference. Using the Clear Info function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTC. With the scan tool, observe the TCC release pressure parameter. Does the scan tool indicate YES for the TCC release pressure parameter? If so, go to next step. If not, go to step 6 .
3. Turn ignition OFF. Disconnect the transaxle in-line 20-pin connector (additional DTCs may set). Connect the Jumper Harness (J 44152) on the engine side of the 20-pin connector. Using the Connector Test Adapter Kit (J 35616-A), connect a fused jumper wire from terminal "U" to a good ground. Turn ignition ON, engine OFF. Observe the TCC release pressure parameter. Does the scan tool indicate YES for the TCC release pressure parameter? If so, go to next step. If not, go to step 5 .
4. Test the signal circuit (CKT 657) of the TCC release switch for an open between the PCM connector and the transaxle in-line 20-pin connector. Did you find and correct a condition? If so, go to step 11 . If not, go to step 10 .
5. Test the signal circuit (CKT 1804) of the TCC release switch for an open between the transaxle in-line 20-pin connector and the TFP manual valve position switch. Did you find a condition? If so, go to step 8 . If not, go to step 9 .
6. Using the scan tool, observe TCC slip speed and TCC release pressure. Drive the vehicle with the gearshift lever in D4 until the TCC is applied and slip speed is below 50 RPM. Does the scan tool indicate YES for the TCC release pressure parameter? If so, go to next step. If not, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article.
7. Inspect for the following conditions of mechanical components and hydraulic circuits that could cause TCC release pressure at the TCC release switch when the TCC is applied: The turbine shaft "O" ring seal leaking. The turbine shaft oil seal rings missing or damaged. The TCC control valve damaged. The No. 1 check ball damaged. The spacer plate release exhaust blocked with debris. The case cover or spacer plate gaskets improperly installed. See appropriate OVERHAUL article. Did you complete the repair? If so, go to step 11 .
8. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 11 .
9. Replace the TFP manual valve position switch. See «TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 11 .
10. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
11. Perform the following procedure to verify the repair: Select DTC. Select Clear Info. Drive the vehicle in D4 until the transaxle shifts to 4th gear and the TCC is commanded ON. Observe TCC release pressure on the scan tool. The TCC release pressure status must indicate NO for at least 3 seconds. Select SPECIFIC DTC. Enter DTC P1887. Has the test run and passed? If so, go to next step. If not, go to step 2 .
12. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.

Note. Do not replace the torque converter for this condition.

Inspect wiring for poor connections at PCM, transaxle in-line 20-pin harness connector and TFP manual valve position switch. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

TRANSAXLE GEARSHIFT LEVER DISPLAY INOPERATIVE OR DISPLAYS INCORRECT RANGE

Note. For circuit identification, see CONNECTOR IDENTIFICATION and WIRING DIAGRAMS .

The transmission internal mode switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission gearshift lever. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P, Parity. See TRANSAXLE RANGE SWITCH LOGIC table.

TRANSAXLE RANGE SWITCH LOGIC

The numbers listed below refer to step numbers in the diagnostic procedure

1. 2 - HI values for all signals in all ranges indicates the ground circuit is OPEN.
2. 3 - With the 20-pin connector disconnected, all signals should indicate HI.
3. 5 - If one circuit affects the other, this indicates a short between the two circuits.
4. 11 - This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.

1. Install a scan tool. Turn ignition ON, engine OFF. Select IMS on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does each range selected match the scan tool IMS display? If so, see «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. If not, go to next step.
2. Select IMS A/B/C/P on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does the IMS A/B/C/P display HI/HI/HI/HI for each range? If so, go to step 12 . If not, go to next step.
3. Turn OFF the ignition. Disconnect the AT inline 20-pin connector. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Do the scan tool IMS A/B/C/P signals all indicate HI? If so, go to next step. If not, go to step 8 .
4. Turn OFF the ignition. Install the Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Turn ON the ignition, with the engine OFF. Using the Digital Multimeter (DMM) (J 39200) and the GM Terminal Test Kit (J 35616-A), measure the voltage at terminal "F" of the jumper harness. Measure the voltage at terminal "G" of the jumper harness. Measure the voltage at terminal "H" of the jumper harness. Measure the voltage at terminal "J" of the jumper harness. Does the voltage measure ignition voltage at all four terminals? If so, go to next step. If not, go to step 9 .
5. Connect a fused jumper wire from terminal "F" of the jumper harness signal "A" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal A circuit (CKT 771) is grounded, do any other signal circuits indicate LOW? If so, go to step 10 . If not, go to next step.
6. Connect a fused jumper wire from terminal "G" of the jumper harness signal "B" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal A circuit (CKT 772) is grounded, do any other signal circuits indicate LOW? If so, go to step 10 . If not, go to next step.
7. Connect a fused jumper wire from terminal "H" of the jumper harness signal "C" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal A circuit (CKT 773) is grounded, do any other signal circuits indicate LOW? If so, go to step 10 . If not, go to next step.
8. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate HI for a short to ground between the PCM connector C1 or C2 and the AT inline 20-pin connector. If the condition has been found and corrected, go to step 17 . If not, go to step 16 .
9. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate ignition voltage for an open between the PCM connector C1 or C2 and the AT inline 20-pin connector. If the condition has been found and corrected, go to step 17 . If not, go to step 16 .
10. Test the affected signal circuits of the IMS for a shorted together condition between the PCM connector C1 or C2 and the AT inline 20-pin connector. If the condition has been found and corrected, go to step 17 . If not, go to step 16 .
11. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS for an open or shorted condition between the AT inline 20-pin connector and the IMS. If the condition was found, go to step 14 . If not, go to step 15 .
12. Test the ground circuit (CKT 451) of the IMS for an open between the AT inline 20-pin connector and the ground connection to the chassis. If the condition has been found and corrected, go to step 17 . If not, go to next step.
13. Test the ground circuit (CKT 1050) of the IMS for an open between the AT inline 20-pin connector and the IMS. If the condition was found, go to next step. If not, go to step 15 .
14. Replace the transaxle internal wiring harness assembly. See «TRANSAXLE INTERNAL WIRING HARNESS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step 17 .
15. Replace the lever assembly-manual shaft detent with internal mode switch. See «PARKING SYSTEM COMPONENTS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. When replacement is complete, go to step 17 .
16. Replace the PCM. See «POWERTRAIN CONTROL MODULE»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e) under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
17. Turn ON the ignition, with the engine OFF. With the scan tool, observe the IMS display while selecting each transmission range: P, R, N, D4, D3, D2, and D1. Does each selected transmission range match the scan tool IMS display? If so, system is OK. If not, go to step 1 .

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension. Check for chafed wire or broken wire inside insulation. Check for moisture and corrosion in wiring and connections. When diagnosing intermittent condition, wiggle wiring harness while watching scan tool for change in value.

SHIFT SOLENOID LEAK TEST

Note. This procedure tests ON/OFF type solenoid valves.

Note. Visually inspect the physical condition of the solenoid before testing. Inspect the "O" rings before and after the test to be sure that they are not cut or damaged.

1. Remove the solenoid from the control valve body.
2. Install the 1-2 or the 2-3 shift solenoid valve into bore number 2 of the Solenoid Testing Kit (J 44246) and install the factory retainer clip to retain the solenoid. (Scheme 315)
3. Connect the solenoid testing harness supplied with the solenoid tester to the solenoid. (Scheme 316)
4. Apply compressed air to the solenoid tester. CAUTION: DO NOT use air pressure in excess of 120 psi (8.44 kg/cm 2 ). Excessive pressure will not allow the solenoid ball check valve to seat properly. Recommended air pressure is 50 psi (3.52 kg/cm 2 ).
5. Air should flow through the solenoid. If air does not flow through the solenoid, replace the solenoid.
6. Connect the solenoid testing harness to the positive and negative battery terminals.
7. Observe if the solenoid is operating electrically. An audible clicking noise can be heard when connecting or disconnecting power.
8. Observe the air flow through the solenoid. The flow will completely or nearly completely stop. Replace the solenoid if there continues to be an obvious air leak when the solenoid is energized. NOTE: All solenoids need to be energized to seal. A small amount of air leakage of about 3 psi (.21 kg/cm 2 ) is normal.
9. Install the solenoid into the control valve body.

Scheme 315

Scheme 316

REMOVAL & INSTALLATION

Removal

1. Remove the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.
2. Disconnect the input speed sensor electrical connector.
3. Remove the input speed sensor clip (441) from the case cover. (Scheme 317)
4. Remove the input speed sensor (440) from the case cover.
5. Inspect the input speed sensor (440) for the following conditions: (Scheme 318) Damaged or missing magnet. Damaged housing. Bent or missing electrical terminals. Damaged speed sensor clip (441).

Scheme 317

Scheme 318

Installation

1. Install the input speed sensor (440) into the case cover. (Scheme 317)
2. Install the input speed sensor clip (441) into the case cover.
3. Connect the input speed sensor electrical connector.
4. Install the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.

Note. Use a piece of wood or rubber when prying with side cutters to remove the manual shaft pin, to prevent damage to the case.

1. Use side cutting pliers in order to remove the manual shift shaft pin (801). (Scheme 319)
2. Disconnect the manual valve link (402) from the IMS/detent lever assembly (811). (Scheme 320)
3. Remove the IMS/detent lever (811) and remove the park pawl actuator assembly (800). CAUTION: The IMS/detent lever (811) should be removed as an assembly.
4. Position the transmission so that the reverse band servo bore is facing upward.
5. Use a small screwdriver in order to pry the manual shift shaft seal (806) from the case. (Scheme 321)
6. Remove the park pawl actuator guide pin (808).
7. Remove the park pawl actuator guide assembly (809) from the case.
8. Remove the actuator guide seal (810) from the guide.
9. To install components, reverse removal procedures.

Scheme 319

Scheme 320

Scheme 321

POWERTRAIN CONTROL MODULE

Service of the PCM should normally consist of either replacement of the PCM or Electrically Erasable Programmable Read Only Memory (EEPROM) programming. If the diagnostic procedures call for PCM replacement, check the PCM first to see if the replacement PCM is the correct part. If the PCM is faulty, remove the PCM and install the new service PCM.

The new service PCM will not be programmed. You must program the new PCM. DTC P0602 indicates the EEPROM is not programmed or has malfunctioned.

1. Disconnect the negative battery cable.
2. Remove the left front inner fender brace.
3. Remove the air cleaner intake duct.
4. Remove the air cleaner housing cover screws (2). (Scheme 322)
5. Remove the air cleaner housing cover (1).
6. Without disconnecting the PCM electrical connectors, remove the PCM and the wiring harness from the air cleaner housing assembly (3).
7. Disconnect the PCM electrical connectors and remove the PCM.

1. Install the PCM to the PCM electrical connectors. Tighten the connectors to specification. See «TORQUE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__torque-specifications).
2. Install the PCM and the wiring harness to the air cleaner housing assembly (3).
3. Install the air cleaner housing cover (1). (Scheme 322)
4. Install the air cleaner housing cover screws (2). Tighten the screws to specification. See «TORQUE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__torque-specifications).
5. Install the air cleaner intake duct.
6. Install the left front inner fender brace.
7. Connect the negative battery cable.
8. The new PCM must be programmed. See appropriate article in ENGINE PERFORMANCE.

Scheme 322

1. Remove the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.
2. Disconnect the pressure control solenoid (PCS) electrical connector.
3. Remove the PCS retaining clip (314E). (Scheme 323)
4. Remove the PCS (322).

Scheme 323

1. Install the PCS (322). (Scheme 323)
2. Install the PCS retaining clip (314E).
3. Connect the PCS electrical connector.
4. Install the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.

1. Remove the left side of the instrument panel (I/P) insulator.
2. Disconnect the electrical connector from the stop lamp switch.
3. Remove the stoplamp switch (2) from the brake pedal bracket. (Scheme 324)

Scheme 324

1. Install the stoplamp switch (2) to the brake pedal bracket. (Scheme 324)
2. Connect the electrical connector to the stoplamp switch.
3. Install the left side of the I/P insulator.
4. Adjust the stoplamp switch.

1. Remove the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.
2. Disconnect and reposition the electrical connectors from the following: (Scheme 325) If equipped internal mode switch. 2-3 Shift solenoid valve assembly (315B). Automatic transaxle fluid pressure manual valve position switch assembly (395).
3. Remove the oil pump bolts (206,207). (Scheme 326) NOTE: DO NOT remove the bolt (205) that holds the oil pump together.
4. Remove the oil pump (200) from the valve body (300). (Scheme 327)
5. Disconnect the torque converter clutch pulse width modulation (TCC PWM) solenoid electrical connector. (Scheme 328)
6. Remove the TCC PWM solenoid retaining clip (314F).
7. Remove the TCC PWM solenoid (334).

Scheme 325

Scheme 326

Scheme 327

Scheme 328

1. Install the TCC PWM solenoid (334). (Scheme 328)
2. Install the TCC PWM solenoid retaining clip (314F).
3. Connect the TCC PWM solenoid electrical connector. (Scheme 325)
4. Install the oil pump (200) to the valve body (300). (Scheme 327)
5. Install the oil pump bolts (206,207). (Scheme 326) Tighten the bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__torque-specifications).
6. Reposition and connect the electrical connectors to the following: Automatic transaxle fluid pressure manual valve position switch assembly (395). 2-3 Shift solenoid valve assembly (315B). If equipped internal mode switch.
7. Install the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.

1. Remove the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.
2. Use a small flat-bladed tool to remove the wiring harness from the solenoid valve(s), TFP manual valve position switch and/or the temperature sensor.
3. Remove the wiring harness. (Scheme 329)

Scheme 329

1. Connect the wiring harness. (Scheme 329)
2. Install the wiring harness to the solenoid valve(s), TFP manual valve position switch and/or the temperature sensor.
3. Install the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.

1. Remove the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.
2. Disconnect the transaxle wiring harness.
3. Remove the control valve body bolts (375, 379 and 381) that mount the fluid pressure manual valve position switch to the control valve body (300). (Scheme 330)
4. Carefully remove the fluid pressure manual valve position switch. Handle the switch carefully, the fluid pressure manual valve position switch is very delicate.
5. Inspect the fluid pressure manual valve position switch (395) for the following conditions: Damaged electrical connector terminals. Damaged seals. Damaged switch membranes. Debris on the switch membranes.

1. Carefully install the fluid pressure manual valve position switch. Handle the switch carefully, the fluid pressure manual valve position switch is very delicate. (Scheme 330)
2. Install the control valve body bolts (375, 379 and 381) that mount the fluid pressure manual valve position switch to the control valve body (300). Tighten control valve body bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-diagnosis-4t65-e__torque-specifications).
3. Connect the transaxle wiring harness.
4. Install the case side cover. See «REMOVAL & INSTALLATION»(/buick/century/vi-1997-2005/remont/automatic-trans/#automatic-transaxle-servicing__removal-installation) in SERVICING - CENTURY & REGAL article.

Scheme 330

Note. For transmission fluid temperature sensor replacement, see TRANSAXLE INTERNAL WIRING HARNESS .

Note. Removal and installation of vehicle speed sensor and input speed sensor is an un-bolt and bolt-on procedure. Only torque specifications are given. See TORQUE SPECIFICATIONS .

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

COMPONENT RESISTANCE

Connect DMM between specified terminals at component or at transaxle in-line 20-pin connector to transaxle. Measure individual component resistance at specified temperature. (Scheme 333)and (Scheme 334). See COMPONENT RESISTANCE. If resistance is not as specified, replace appropriate component. (Scheme 332)

COMPONENT RESISTANCE

Scheme 331

Scheme 332

Scheme 333

Scheme 334

Scheme 335

Scheme 336

Scheme 337

Scheme 338

Scheme 339

Scheme 340

Scheme 341

Scheme 342

Scheme 343

Scheme 344

Transaxle Electronic Control System Wiring Diagram (2003 Century). Scheme 345

Transaxle Electronic Control System Wiring Diagram (2003 Regal). Scheme 346

See also:
• DESCRIPTION & OPERATION
• CHECKING FLUID LEVEL & CONDITION
• REMOVAL & INSTALLATION - CENTURY & REGAL
• ADJUSTMENTS
• COMPONENT DISASSEMBLY & REASSEMBLY
• VEHICLE SPEED SENSOR
• DRAINING & REFILLING
• REMOVAL & INSTALLATION
• SHIFT SOLENOID VALVE OPERATION & GEAR RATIOS
• PC SOLENOID VALVE DUTY CYCLE
• TRANSMISSION FLUID TEMPERATURE SENSOR
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• SYMPTOM DIAGNOSIS
• PRELIMINARY INSPECTION
• DTC P0741: TCC SYSTEM STUCK OFF
• DTC P0742: TCC SYSTEM STUCK ON
• DTC P1887: TORQUE CONVERTER CLUTCH RELEASE SWITCH CIRCUIT MALFUNCTION
• SHIFT SPEED SPECIFICATIONS
• TORQUE SPECIFICATIONS
• P0218
• P0502
• P0503
• P0711
• P0712
• P0713
• P0716
• P0717
• P0719
• P0724
• P0730
• P0748
• P0751
• P0752
• P0753
• P0756
• P0757
• P0758
• P1811
• P1814
• P1860
• CLEARING DIAGNOSTIC TROUBLE CODES
• TROUBLE SHOOTING
• HYDRAULIC PRESSURE TESTS