Automatic Transmission Diagnosis- 4l80-e (diesel - 4-digit Codes) GMC Savana I

APPLICATION

Note. This article applies to "C", "G", "K" and "P" series vehicles equipped with 6.5L diesel engines (RPO L57 and L65) with Electronic Fuel Injection (EFI). These applications utilize a Powertrain Control Module (PCM) capable of producing 4-digit Diagnostic Trouble Codes (DTC). For "P" series vehicles equipped with 6.5L diesel engines (RPO L57) with Mechanical Fuel Injection (MFI), see HYDRA-MATIC 4L80-E ELECTRONIC CONTROLS - 2-DIGIT CODES - DIESEL article.

4L80-E TRANSMISSION APPLICATIONS

MODEL IDENTIFICATION

Vehicle model is identified by fifth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

MODEL IDENTIFICATION

INTRODUCTION

The 4L80-E transmission utilizes 2 electronic shift solenoids to control transmission upshifts and downshifts. In addition, a pressure control solenoid controls hydraulic line pressure, and a Torque Converter Clutch (TCC) Pulse Width Modulated (PWM) solenoid controls the fluid acting on TCC valve which in turn, controls TCC apply and release. Solenoids are actuated on and off by Powertrain Control Module (PCM).

The PCM receives signals from various transmission sensors. Sensor signals include: engine speed and throttle position, transmission speed, hydraulic pressure and transmission fluid temperature. The PCM incorporates an on-board self-diagnostic system to help identify any components or circuits which may need further testing.

Shift solenoids hold hydraulic pressure (solenoid on) or releases hydraulic pressure (solenoid off). This action controls shift valves inside valve body. By switching one or both solenoids on or off, different combinations of clutches, sprags and bands are operated.

POWERTRAIN CONTROL MODULE (PCM)

The PCM controls TCC, pressure control solenoid (hydraulic pressure), and shift solenoid valves 1-2 and 2-3. In addition, PCM also controls engine-related systems.

The PCM receives electronic signals from sensors and switches. These signals help PCM determine when to operate various relays and solenoids related to engine and transmission components. On "C" and "K" series, PCM is located behind right side of instrument panel, above blower motor. On "G" series, PCM is located behind center of instrument panel. On "P" series, PCM is located behind left side of instrument panel.

LIMP-IN MODE

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

Note. Malfunction Indicator Light (MIL) located on instrument cluster is also referred to as SERVICE ENGINE SOON light.

SENSORS & SWITCHES

The PCM controls torque converter clutch lock-up, upshifts and downshifts based on transmission temperature, system voltage, throttle position, transmission oil pressure switches, and transmission input and output speed sensors. (Scheme 148) For additional information and testing of engine components, see SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article in ENGINE PERFORMANCE.

Shift Solenoids

Transmission is shifted up or down by 2 electronic shift solenoids. Both solenoids are located on valve body. (Scheme 148) Ignition voltage is supplied to each solenoid by TRANS fuse (10-amp) located in instrument panel fuse block. The 1-2 shift solenoid controls hydraulic pressure to 1-2 and 3-4 shift valves. The 2-3 shift solenoid controls hydraulic pressure to 2-3 shift valve.

Pressure Control Solenoid

Pressure control solenoid has a spool valve and operates pressure regulator valve. (Scheme 148) The PCM sends a frequency signal to pressure control solenoid to regulate hydraulic line pressure. Frequency signal (duty cycle) is measured with a dwell meter or lab scope. When duty cycle is zero, line pressure is at maximum, and pressure control solenoid draws zero amps. When duty cycle is 60 percent, line pressure is at minimum, and pressure control solenoid draws 1.1 amps at 4.5 volts.

TCC PWM Solenoid

This solenoid is used to control TCC apply valve. PCM delivers a frequency signal to TCC PWM solenoid to gradually apply or release TCC. (Scheme 148)

Note. TCC PWM solenoid may also be referred to as TCC solenoid.

Scheme 148

SELF-DIAGNOSTIC SYSTEM

The PCM continuously monitors all electrical circuits. If PCM detects circuit problems or out-of-range sensors, it will record a Diagnostic Trouble Code (DTC). If problem continues for a predetermined amount of time, Malfunction Indicator Light (MIL) will illuminate.

If MIL remains illuminated, DTC(s) are currently being detected. If MIL is off, but PCM had detected a circuit or sensor problem, DTC(s) will be stored in computer memory.

Stored DTCs may be retrieved from PCM memory using a scan tool. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under DIAGNOSIS & TESTING. DTCs CANNOT be retrieved by grounding 16-pin Data Link Connector (DLC).

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

PRELIMINARY INSPECTION

Note. The preliminary inspection is very important and should be performed carefully and thoroughly, as it can often fix a problem without requiring further diagnosis.

1. Check transmission fluid level and condition. Inspect all wire harnesses and connections leading to transmission. Verify brake system is operational and not dragging.
2. Check all vacuum hoses for correct routing, restrictions, cuts or other damage. Inspect difficult to see vacuum hoses beneath air cleaner assembly and other engine components.
3. Inspect all engine compartment wiring for proper connections. Check wires for pinched or chafed spots, as well as contact with sharp edges or exhaust manifolds.
4. Repair any problems as necessary. If no problems are found during preliminary inspection, begin diagnosis of transmission electronic control system. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__on-board-diagnostic-obd-system-check) under DIAGNOSIS & TESTING.

NO DATA LINK CONNECTOR (DLC) DATA

Note. If scan tool does not display PCM data, see DATA LINK CONNECTOR (DLC) DIAGNOSIS under CIRCUIT TESTS in SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE.

MIL INOPERATIVE

Note. If MIL does not illuminate, see NO MALFUNCTION INDICATOR LIGHT (MIL) under CIRCUIT TESTS in SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE.

COMPONENT & WIRE HARNESS RESISTANCE CHECKS

Note. The following test procedure includes resistance checks for each transmission component and its connecting wire harness. When taking resistance measurements, compare readings taken in each step to the proper values listed. See COMPONENT/CIRCUIT RESISTANCE SPECIFICATIONS table. For circuit identification, see CONNECTOR IDENTIFICATION under DIAGNOSIS & TESTING.

1. Connect Jumper Harness (J-39775) to 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "A" and "E" (1-2 shift solenoid valve circuits). If resistance is as specified, go to step 3 . If resistance is not as specified, go to next step.
2. Disconnect 1-2 shift solenoid valve from transmission wire harness assembly. Measure resistance of 1-2 shift solenoid valve. If resistance is as specified, go to step 12 . If resistance is not as specified, go to step 14 .
3. Measure resistance between terminals "B" and "E" (2-3 shift solenoid valve circuits). If resistance is as specified, go to step 5 . If resistance is not as specified, go to next step.
4. Disconnect 2-3 shift solenoid valve from transmission wire harness assembly. Measure resistance of 2-3 shift solenoid valve. If resistance is as specified, go to step 12 . If resistance is not as specified, go to step 14 .
5. Measure resistance between terminals "S" and "E" (TCC solenoid valve circuits). If resistance is as specified, go to step 7 . If resistance is not as specified, go to next step.
6. Disconnect TCC solenoid valve from transmission wire harness assembly. Measure resistance of TCC solenoid valve. If resistance is as specified, go to step 12 . If resistance is not as specified, go to step 14 .
7. Measure resistance between terminals "C" and "D" (pressure control solenoid valve circuits). If resistance is as specified, go to step 9 . If resistance is not as specified, go to next step.
8. Disconnect pressure control solenoid valve from transmission wire harness assembly. Measure resistance of pressure control solenoid valve. If resistance is as specified, go to step 12 . If resistance is not as specified, go to step 14 .
9. Measure resistance between terminals "L" and "M" (TFT sensor circuits). If resistance is as specified, go to next step. If resistance is not as specified, go to step 12 .
10. Measure resistance between transmission case and terminals "A", "B", "C", "D", "E", "L", "M", "N", "P", "R" and "S" at 20-pin transmission harness connector (transmission side). If resistance is greater than 250 k/ohms, harness is okay. If resistance is not greater than 350 k/ohms, go to next step.
11. Disconnect transmission harness assembly from all transmission components. Measure resistance between transmission case and all component terminals. If resistance is greater than 250 k/ohms, go to next step. If resistance is not greater than 250 k/ohms, go to step 14 .
12. Inspect wire harness for poor connections at transmission components or at vehicle harness. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Inspect for broken wires inside their insulation. If diagnosing for an intermittent short or open conditions, move wire harness while monitoring test equipment for value changes. If a problem is found, go to next step. If wire harness and connections are okay, system is okay.
13. Replace internal transmission wire harness assembly.
14. Replace faulty component.

COMPONENT/CIRCUIT RESISTANCE SPECIFICATIONS

TFP MANUAL VALVE POSITION SWITCH & WIRE HARNESS RESISTANCE CHECKS

1. Connect Jumper Harness (J-39775) to 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between transmission case and terminal "N" (range signal "A" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, go to step 3 . If resistance is not greater than 50 k/ohms, go to next step.
2. Disconnect wire harness from TFP valve position switch. Measure resistance between TFP valve position switch housing and terminal "A" at TFP valve position switch. If resistance is greater than 50 k/ohms, go to step 15 . If resistance is not greater than 50 k/ohms, go to step 16 .
3. Measure resistance between transmission case and terminal "R" (range signal "B" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, go to step 5 . If resistance is not greater than 50 k/ohms, go to next step.
4. Disconnect wire harness from TFP valve position switch. Measure resistance between TFP valve position switch housing and terminal "B" at TFP valve position switch. If resistance is greater than 50 k/ohms, go to step 15 . If resistance is not greater than 50 k/ohms, go to step 16 .
5. Measure resistance between transmission case and terminal "P" (range signal "C" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, go to step 7 . If resistance is not greater than 50 k/ohms, go to next step.
6. Disconnect wire harness from TFP valve position switch. Measure resistance between TFP valve position switch housing and terminal "C" at TFP valve position switch. If resistance is greater than 50 k/ohms, go to step 15 . If resistance is not greater than 50 k/ohms, go to step 16 .
7. Set parking brake. Start engine and allow it to idle. Place gear selector in Drive ("D4" position). Measure resistance between transmission case and terminal "R" (range signal "B" circuit) at TFP valve position switch harness connector. If resistance is less than 200 ohms, go to next step. If resistance is not less than 200 ohms, go to step 14 .
8. With gear selector in Drive ("D4" position), measure resistance between transmission case and terminal "P" (range signal "C" circuit) at TFP valve position switch harness connector. If resistance is less than 200 ohms, go to next step. If resistance is not less than 200 ohms, go to step 14 .
9. Place gear selector in Low ("D1" position). Measure resistance between transmission case and terminal "N" (range signal "A" circuit) at TFP valve position switch harness connector. If resistance is less than 200 ohms, go to next step. If resistance is not less than 200 ohms, go to step 14 .
10. With gear selector in Low ("D1" position), measure resistance between transmission case and terminal "P" (range signal "C" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, go to next step. If resistance is not greater than 50 k/ohms, go to step 16 .
11. Place gear selector in Reverse. Measure resistance between transmission case and terminal "N" (range signal "A" circuit) at TFP valve position switch harness connector. If resistance is less than 200 ohms, go to next step. If resistance is not less than 200 ohms, go to step 16 .
12. With gear selector in Reverse, measure resistance between transmission case and terminal "P" (range signal "C" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, go to next step. If resistance is not greater than 50 k/ohms, go to step 16 .
13. Place gear selector in manual 3rd ("D3" position). Measure resistance between transmission case and terminal "R" (range signal "B" circuit) at TFP valve position switch harness connector. If resistance is greater than 50 k/ohms, system is okay. If resistance is not greater than 50 k/ohms, go to step 16 .
14. Disconnect wire harness from TFP valve position switch. Check wires in harness for an open. If any circuits are open, go to next step. If all circuits are okay, go to step 16 .
15. Replace wire harness assembly. After repairs, go to step 1 .
16. Replace TFP valve position switch. After repairs, go to step 1 .

DIAGNOSIS & TESTING

Note. Most problems that exist with MIL or diagnostic system are engine performance or PCM related. Procedures for repairing these systems and circuits may require additional engine performance repair data. The following tests contain references to additional procedures not found in this publication.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. The OBD system check is an organized approach to identifying conditions created by a control module system malfunction, and MUST be the starting point for any driveability diagnosis. A scan tool is required to perform OBD system check.

Circuit Description

The OBD system check determines

1. If Malfunction Indicator Light (MIL) is operational.
2. If PCM is operating and can recognize a fault.
3. If any Diagnostic Trouble Codes (DTC) are stored.

If no DTCs are indicated after performing OBD system check and driveability problems still exist, diagnose by symptom. See TROUBLE SHOOTING - NO CODES - TRUCKS article in ENGINE PERFORMANCE.

Diagnostic Procedure

Note. Ensure battery is fully charged and check for applicable Technical Service Bulletins (TSB) before proceeding. DO NOT turn ignition off during the following procedure unless instructed to do so.

1. Check for one or more of the following conditions: Malfunction Indicator Light (MIL) illuminated with engine running. Confirmed customer driveability concern. Suspected fault in computerized engine control system. If any conditions are present, go to next step. If specified conditions are not present, system is okay at this time. Check for an intermittent problem. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - TRUCKS article in ENGINE PERFORMANCE.
2. Turn ignition on, engine off. Observe MIL. If MIL illuminates, go to next step. If MIL does not illuminate, see «MIL INOPERATIVE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__mil-inoperative) under SYMPTOM TESTS.
3. Turn ignition off. Connect scan tool following scan tool manufacturer's instructions. Turn ignition on, engine off. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, see «NO DATA LINK CONNECTOR (DLC) DATA»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__no-data-link-connector-dlc-data) under SYMPTOM TESTS.
4. Attempt to start engine. If engine starts and runs, go to next step. If engine will not run, see appropriate NO START-ENGINE CRANKS OKAY test procedure under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - TRUCKS - EXCEPT TRACKER article in ENGINE PERFORMANCE.
5. Observe DTC data. If no DTCs are set, go to next step. If any DTCs are set, save freeze frame data using scan tool, and identify DTCs to be diagnosed. See «DIAGNOSTIC TROUBLE CODE IDENTIFICATION»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) table.
6. If MIL is illuminated and no DTCs are set, diagnose using diagnostic procedure for DTC P1641. See DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE. If MIL is off and no DTCs are set, go to next step.
7. Compare scan tool data with specified values. See SCAN TOOL DATA under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE. If displayed values are within specified ranges, suspect an intermittent fault. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - TRUCKS article in ENGINE PERFORMANCE. If displayed values are not within specified ranges, diagnose suspect component. See SYSTEM & COMPONENT TESTING - TRUCKS - EXCEPT TRACKER article in ENGINE PERFORMANCE.

Note. Only transmission-related DTCs are listed. For engine-related DTC identification, see TROUBLE CODE DEFINITIONS article in APPLICATIONS & IDENTIFICATION. For engine-related DTC diagnosis, see SELF-DIAGNOSTICS - DIESEL article in ENGINE PERFORMANCE. These DTCs pertain to engine performance and must be repaired first, as engine performance and related component signals will affect transmission operation and diagnosis.

DIAGNOSTIC TROUBLE CODE IDENTIFICATION (1)

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

During any diagnostic procedure, it must be determined if DTCs are hard failure DTCs or intermittent failure DTCs. Diagnostic tests will not usually help analyze intermittent DTCs. To determine hard DTCs and intermittent DTCs, proceed as follows

1. Perform OBD system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__on-board-diagnostic-obd-system-check) . Read and record all stored DTCs. After completed, clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__clearing-diagnostic-trouble-codes) .
2. Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL should turn off. Run warm engine at curb idle for 2 minutes and note MIL.
3. If MIL illuminates, perform OBD system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__on-board-diagnostic-obd-system-check) . Read and record DTCs. This will reveal hard failure DTCs. DTCs may require a road test to reset hard failure after clearing DTC. If MIL does not illuminate, all stored DTCs were intermittent failures.

CLEARING DIAGNOSTIC TROUBLE CODES

DTCs can be cleared using scan tool. If scan tool is not available, turn ignition off. Remove control module fuse from fuse block for 30 seconds. Replace fuse. If fuse cannot be located, disconnect PCM pigtail at battery for 30 seconds. DTCs may also be cleared by disconnecting negative battery cable. However, this may result in loss of other on-board memory data, such as preset radio tuning. After power to PCM is removed, poor driveability may occur until control module "relearns" operating parameters.

DTCs will also be cleared under the following conditions: PCM will turn off MIL after 3 consecutive ignition cycles without a failure reported. PCM will cancel DTC default actions when fault no longer exists and ignition is cycled off long enough to power down PCM. DTC will be cleared when vehicle has achieved 40 warm-up cycles without a failure reported.

CONNECTOR IDENTIFICATION

Note. For connector identification, refer to illustrations. (Scheme 149)- (Scheme 152). For internal transmission wire harness circuit identification, see 20-PIN TRANSMISSION WIRE HARNESS CIRCUIT IDENTIFICATION table.

Scheme 149

Scheme 150

Scheme 151

Scheme 152

20-PIN TRANSMISSION WIRE HARNESS CIRCUIT IDENTIFICATION

DIAGNOSTIC TESTS

Note. Not all DTCs are applicable to all models.

The following diagnostic procedures are DTC specific. Always perform OBD system check prior to performing diagnostic procedures, and upon completion of any repairs. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under DIAGNOSIS & TESTING. For PCM terminal identification, see CONNECTOR IDENTIFICATION under DIAGNOSIS & TESTING. For wire color and circuit identification, see WIRING DIAGRAMS .

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within transmission wiring harness. TFT sensor controls signal voltage to PCM. PCM provides a 5-volt reference to sensor on TFT sensor signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases.

Conditions For Setting DTC P0218

DTC will set under the following conditions

1. Transmission fluid temperature greater than 266°F (130°C).

Action Taken By PCM

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Does not illuminate MIL.
3. Stores DTC P0218 PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Check transmission fluid, and fill if necessary. Go to next step.
2. If DTC P0711 was also set, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__diagnostic-aids) . If DTC P0711 was not set, go to next step.
3. Inspect cooling system for air flow restrictions, blockage and debris. Check transmission cooling system for air flow restrictions, blockage, debris, damaged cooler lines or hoses and low ATF flow. If a problem is found, go to step 6 . If cooling systems are okay, go to next step.
4. Check transmission line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is not to specification, repair as necessary. After repairs, go to step 6 . If line pressure is okay, go to next step.
5. Check torque converter stator for damage. See TORQUE CONVERTER under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If stator is faulty, replace torque converter. After repairs, go to next step. If stator is okay, diagnose transmission overheating by symptom. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article.
6. Using scan tool, clear DTCs. Turn ignition on. Ensure TFT value is less than 264°F (129°C) for at least 5 seconds. Check for DTCs. If no DTCs are set, system is okay. If DTC P0218 is set, go to step 1 .

Diagnostic Aids

Inspect cooling system fluid level and condition. Check transmission cooler and cooler lines for damage and restrictions. TFT sensor temperature should increase steadily, and then stabilize. Check for torque converter stator malfunction. Check customer driving habits (towing in incorrect gear). DTC P0218 may set about 10 minutes after DTC P0711 (TFT sensor circuit range/performance) has set. Follow diagnostic procedure for DTC P0711 before performing diagnostic procedure for this DTC. Repairing condition that set DTC P0711 will most likely eliminate DTC P0218. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset.

PCM monitors fused battery and ignition voltage circuits for low or high system voltage.

Conditions For Setting DTC P0560

DTC will set under the following conditions

1. For low system voltage, engine speed is greater than 1500 RPM and system voltage is less than 10.5 volts at a maximum transmission temperature of 306°F (152°C), or less than 6.7 volts at a minimum transmission temperature of -40°F (-40°C).
2. For high system voltage, system voltage is greater than 19 volts for 10 seconds.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Turns off pressure control solenoid.
3. Inhibits TCC engagement.
4. Commands an immediate shift into 2nd gear.
5. Does not illuminate MIL.
6. Stores DTC P0560 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Measure voltage across battery terminals. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10 volts, check battery and charging system. Repair as necessary.
2. Start engine and allow it to reach normal operating temperature. If GENERATOR/CHECK ENGINE light is illuminated, check battery and charging system. Repair as necessary. If GENERATOR/CHECK ENGINE light is not illuminated, go to next step.
3. With DVOM connected across battery terminals, turn headlights and blower motor on. Increase engine speed to 1500 RPM. If voltage is 13-15 volts, go to next step. If voltage is not 13-15 volts, check battery and charging system. Repair as necessary.
4. With engine speed at 1500 RPM, monitor ignition voltage with scan tool. If voltage is 13-15 volts, system is okay. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If voltage is not 13-15 volts, go to next step.
5. With headlights and blower motor on and engine speed at 1500 RPM, measure voltage (backprobe) between ground and terminals C11 (ignition feed circuit), and then C13 (battery feed circuit) at Blue 32-pin PCM harness connector. If voltage difference is greater than .5 volt from voltage measurement taken in step 3 , go to next step. If voltage difference is not greater than .5 volt from voltage measurement taken in step 3 , go to step 9 .
6. If voltage difference was at terminal C11 (ignition feed circuit), go to next step. If voltage difference was not at terminal C11 (ignition feed circuit), go to step 8 .
7. Repair high resistance in ignition feed circuit. After repairs, go to step 10
8. Repair high resistance in battery feed circuit. After repairs, go to step 10
9. Replace PCM. After repairs, go to next step.
10. Using scan tool, clear DTCs. Start engine and allow it to reach normal operating temperature. Ensure ignition voltage displayed on scan tool is 8.3-16.6 volts (12-18 volts on "C" and "K" series). Check for DTCs. If no DTCs are set, system is okay. If DTC P0560 is set, go to step 1 .

Charging battery with battery charger or jump starting vehicle could set DTC P0560. If DTC sets when accessories are operated, check for poor system connections or excessive current draw. Inspect starter solenoid for faulty connections. Inspect starter solenoid fusible link. Check drive belts for wear or incorrect tension. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset.

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within transmission wiring harness. TFT sensor controls signal voltage to PCM. PCM supplies a 5-volt reference signal to sensor. When transmission fluid temperature is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases.

Conditions For Setting DTC P0711

DTC will set under the following conditions

1. TFT sensor is stuck at low temperature.
2. TFT sensor is stuck at high temperature.
3. TFT sensor change is unrealistic.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Uses a default transmission fluid temperature value.
3. Does not illuminate MIL.
4. Stores DTC P0711 in PCM history.

1. Check transmission fluid level. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. While monitoring TFT sensor value on scan tool, test drive vehicle. If TFT sensor value does not change, or changes unrealistically, go to next step. If TFT sensor value appears accurate, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. If scan tool displays an unrealistic TFT sensor value, go to next step. If TFT sensor value did not change, record value, and then go to step 5 .
4. Turn ignition off. Disconnect 20-pin transmission harness connector. Using Connector Test Adapter test Kit (J-35616), connect test light between terminals "L" and "M" of engine side of 20-pin transmission harness connector. Turn ignition on. If scan tool displays an unrealistic TFT sensor value, go to step 6 . If scan tool does not display an unrealistic TFT sensor value, go to step 7 .
5. Turn ignition off. Disconnect 20-pin transmission harness connector. Turn ignition on. If TFT sensor value displayed on scan tool is identical as value recorded in step 3 , go to next step. If values are not identical, go to step 7 .
6. Replace PCM. After repairs, go to step 8 .
7. Replace TFT sensor. After repairs, go to next step.
8. Using scan tool, clear DTCs. Start engine and allow it to reach normal operating temperature. Check for DTCs. If no DTCs are set, system is okay. If DTC P0711 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out or broken terminals, or misaligned connectors. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. Check for moisture and corrosion. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0218 (transmission fluid overtemperature) is also set, inspect transmission cooling system for blockage and restrictions. DTC P0218 may set about 10 minutes after DTC P0711 has set. If DTC P0711 is also set, perform diagnostic procedure for that DTC before diagnosing DTC P0218. Repairing condition that caused DTC P0711 will probably eliminate DTC P0218.

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within transmission wiring harness. TFT sensor controls signal voltage to PCM. PCM provides a 5-volt reference to sensor on TFT sensor signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases.

Conditions For Setting DTC P0712

DTC will set under the following conditions

1. TFT sensor indicates 302°F (150°C) for 15 seconds.

PCM performs the following if DTC is set

1. Commands increased line pressure.
2. Freezes shift adapts from being updated.
3. PCM uses default transmission fluid temperature.
4. Does not illuminate MIL.
5. Stores DTC P0712 in PCM history.

1. Check transmission fluid level. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Monitor TFT sensor voltage with scan tool. If TFT sensor voltage is less than .13 volt, go to next step. If TFT sensor voltage is not less than .13 volt, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Turn ignition off. Disconnect 20-pin transmission harness connector. Turn ignition on. Monitor TFT sensor voltage with scan tool. If TFT sensor voltage is greater than 4.92 volts, go to next step. If TFT sensor voltage is not greater than 4.92 volts, go to step 8 .
4. Turn ignition off. Connect Jumper Harness (J-39775) to transmission side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "L" and "M". If resistance is 133 ohms at 230°F (110°C), or 16 k/ohms at 14°F (-10°C), go to next step. If resistance is not as specified, go to step 6 .
5. Measure resistance between transmission case and terminal "L". If resistance is less than 50 ohms, go to next step. If resistance is not less than 50 ohms, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
6. Disconnect TFT sensor. Measure resistance between terminals "L" and "M" of jumper harness. If resistance is less than 50 ohms, go to step 9 . If resistance is not less than 50 ohms, go to next step.
7. Replace TFT sensor. After repairs, go to step 12 .
8. Check TFT sensor signal circuit for short to ground. If circuit is shorted, repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 10 .
9. Replace transmission wire harness assembly. After repairs, go to step 12 .
10. Check for faulty PCM harness connections. If connections are faulty, repair as necessary. After repairs, go to step 12 . If connections are okay, go to next step.
11. Replace PCM. After repairs, go to next step.
12. Using scan tool, clear DTCs. Ensure scan tool indicates TFT sensor voltage greater than .16 volt for 10 seconds. Check for DTCs. If no DTCs are set, system is okay. If DTC P0712 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. TFT sensor temperature should increase steadily, and then stabilize. If DTC P0218 is also set, check transmission cooling system for possible blockage and/or restrictions. Test TFT sensor at various temperatures to evaluate for skewed sensor. TFT sensor resistance should be 3333-3689 at 68°F (20°C). A skewed sensor may cause delayed garage shifts or TCC complaints. Check customer driving habits, such as towing in overdrive.

The Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within transmission wiring harness. TFT sensor controls signal voltage to PCM. PCM provides a 5-volt reference to sensor on TFT sensor signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases.

Conditions For Setting DTC P0713

DTC will set under the following conditions

1. TFT sensor indicates a voltage greater than 4.94 volts for a predetermined amount of time.

PCM performs the following if DTC is set

1. PCM uses default transmission fluid temperature.
2. Freezes shift adapts from being updated.
3. Does not illuminate MIL.
4. Stores DTC P0713 in PCM history.

1. Check transmission fluid level. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Monitor TFT sensor voltage with scan tool. If voltage is greater than 4.92 volts, go to next step. If voltage is not greater than 4.92 volts, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. If TFT sensor voltage is greater than 5.1 volts, go to step 10 . If TFT sensor voltage is not greater than 5.1 volts, go to next step.
4. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39775) to engine side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure voltage between ground and jumper harness terminal "L". Turn ignition on. If voltage is 4.8-5.2 volts, go to next step. If voltage is not 4.8-5.2 volts, go to step 9 .
5. Turn ignition off. Connect fused jumper wire between terminals "L" and "M" at 20-pin transmission harness connector. Turn ignition on. If TFT sensor voltage is less than .2 volt, go to next step. If TFT sensor voltage is not less than .2 volt, go to step 11 .
6. Turn ignition off. Connect Jumper Harness (J-39775) to transmission side of 20-pin transmission harness connector. Measure resistance between terminals "L" and "M". If resistance is 133 ohms at 230°F (110°C), or 16 k/ohms at 14°F (-10°C), see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If resistance is not as specified, go to next step.
7. Turn ignition off. Remove transmission oil pan. Check for an open in TFT sensor signal circuit or sensor ground circuit. If circuit(s) is open, go to next step. If circuit(s) is okay, go to step 14 .
8. Replace transmission wire harness assembly. After repairs, go to step 15 .
9. Check TFT sensor signal circuit for an open or high resistance. If circuit is faulty, repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 12 .
10. Check TFT sensor signal circuit for short to battery voltage. If circuit is shorted, repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 12 .
11. Check for an open in TFT sensor ground circuit. If circuit is open, repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
12. Check for faulty PCM harness connections. If connections are faulty, repair as necessary. After repairs, go to step 15 . If connections are okay, go to next step.
13. Replace PCM. After repairs, go to step 15 .
14. Replace TFT sensor. After repairs, go to next step.
15. Using scan tool, clear DTCs. Operate vehicle until scan tool indicates TFT sensor voltage less than 4.92 volts for 10 seconds. Check for DTCs. If no DTCs are set, system is okay. If DTC P0713 sets, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. Check engine and transmission wiring harnesses for an open condition. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. TFT sensor temperature should increase steadily, and then stabilize. Test TFT sensor at various temperatures to evaluate for skewed sensor. TFT sensor resistance should be 3333-3689 at 68°F (20°C). A skewed sensor may cause firm shifts or TCC complaints.

Transmission input speed sensor consists of a permanent magnet surrounded by a coil of wire. Rotation of forward clutch housing induces an AC voltage in circuit. Signal voltage and frequency vary with forward clutch rotational speed. PCM converts AC voltage into a digital signal. AC voltage level increases as turbine shaft speed increases. PCM determines actual turbine speed using digital signal. PCM uses input speed to calculate torque converter slip speed and gear ratios.

Conditions For Setting DTC P0716

DTC will set under the following conditions

1. Input speed varies by more than 1300 RPM within 4.9 seconds on "C" and "K" series.
2. Input speed varies by more than 1200 RPM within 4 seconds on "G" and "P" series.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0716 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. With engine speed at 2000 RPM, monitor ISS sensor RPM with scan tool. If ISS sensor RPM changes more than 1200 RPM with engine speed steady, go to next step. If ISS sensor RPM does not change more than 1200 RPM with engine speed steady, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Turn ignition off. Disconnect ISS sensor. Measure ISS sensor resistance. If resistance is 1042-2088 ohms, go to next step. If resistance is not 1042-2088 ohms, go to step 14 .
3. Using DVOM set to AC scale, measure voltage at ISS sensor terminals with engine running at 2000 RPM. If AC voltage is greater than 10 volts and steady, go to next step. If AC voltage is not greater than 10 volts or is not steady, go to step 14 .
4. Turn ignition off. Set DVOM to DC scale. Turn ignition on, engine off. Measure voltage between ground and terminal "A" (ISS sensor high circuit), and then between ground and terminal "B" (ISS sensor low circuit) at ISS sensor harness connector. If either voltage reading is greater than 10.5 volts, go to next step. If neither voltage reading is greater than 10.5 volts, go to step 7 .
5. Check ISS sensor circuits for short to power. If circuit(s) is shorted, go to next step. If circuit(s) is okay, go to step 15 .
6. Repair shot to power in ISS sensor circuit(s). After repairs, go to step 17 .
7. Turn ignition off. Reconnect ISS sensor. Disconnect Brown 32-pin PCM harness connector. With DVOM set to AC scale, measure voltage between terminals D1 (ISS sensor low circuit) and D11 (ISS sensor high circuit) at PCM harness connector. Remove ECM-B fuse (20-amp) located in underhood fuse/relay center. Crank engine. If voltage is greater than .4 volt and steady, go to step 15 . If voltage is not greater than .4 volt or is not steady, go to next step.
8. Turn ignition off. Measure resistance between terminals D1 (ISS sensor low circuit) and D11 (ISS sensor high circuit) at PCM harness connector. If resistance is 1042-2088 ohms, go to next step. If resistance is not 1042-2088 ohms, go to step 11 .
9. Measure resistance between ground and terminal D1 (ISS sensor low circuit), and then between ground and terminal D11 (ISS sensor high circuit) at PCM harness connector. If either resistance measurement is less than 50 k/ohms, go to next step. If neither resistance measurement is less than 50 k/ohms, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
10. Repair short to ground in ISS sensor circuit(s). After repairs, go to step 17 .
11. If resistance measured in step 8 is less than 1042 ohms, go to next step. If resistance measured in step 8 is not less than 1042 ohms, go to step 13 .
12. Repair ISS sensor circuits for short together. After repairs, go to step 17 .
13. Repair high resistance or open in ISS sensor circuit(s). After repairs, go to step 17 .
14. Replace ISS sensor. After repairs, go to step 17 .
15. Check for faulty PCM harness connections. If connections are faulty, repair as necessary. After repairs, go to step 17 . If connections are okay, go to next step.
16. Replace PCM. After repairs, go to next step.
17. Using scan tool, clear DTCs. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000 RPM. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0716 is set, go to step 1 .

Inspect wiring for poor connections at PCM, 20-pin transmission harness connector and ISS sensor. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related or TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. Check for misrouted ISS sensor harness. Wiring may be near DIS components or ignition wires.

Transmission input speed sensor consists of a permanent magnet surrounded by a coil of wire. Rotation of forward clutch housing induces an AC voltage in circuit. Signal voltage and frequency vary with forward clutch rotational speed. PCM converts AC voltage into a digital signal. AC voltage level increases as turbine shaft speed increases. PCM determines actual turbine speed using digital signal. PCM uses input speed to calculate torque converter slip speed and gear ratios.

Conditions For Setting DTC P0717

DTC will set under the following conditions

1. Measured input speed is less than 100 RPM for at least 5 seconds on "C" and "K" series.
2. Measured input speed is less than 50 RPM for at least 5 seconds on "G" and "P" series.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0717 in PCM history.

Note. If other DTCs are present, diagnose them before proceeding.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Disconnect ISS sensor. Measure resistance between ISS sensor terminals. If resistance is 1042-2088 ohms, go to next step. If resistance is not 1042-2088 ohms, go to step 8 .
2. With DVOM connected to ISS sensor terminals, select AC scale. Start engine and increase engine speed to greater than 700 RPM. If AC voltage is greater than 3 volts, go to next step. If AC voltage is not greater than 3 volts, go to step 8 .
3. Turn ignition off. Reconnect ISS sensor. Disconnect Brown 32-pin PCM harness connector. With DVOM set to AC scale, measure voltage between terminals D1 (ISS sensor low circuit) and D11 (ISS sensor high circuit) at PCM harness connector. Remove ECM-B fuse (20-amp) located in underhood fuse/relay center. Crank engine. If AC voltage is greater than .4 volts, go to step 9 . If voltage is not greater than .4 volts, go to next step.
4. Check ISS sensor high circuit for an open, short to ground or short to battery voltage. If circuit is faulty, go to step 6 . If circuit is okay, go to next step.
5. Check ISS sensor low circuit for an open or short to battery voltage. If circuit is faulty, go to step 7 . If circuit is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
6. Repair ISS sensor high circuit. After repairs, go to step 11 .
7. Repair ISS sensor low circuit. After repairs, go to step 11 .
8. Replace ISS sensor. After repairs, go to step 11 .
9. Check for faulty PCM harness connections. If connections are faulty, repair as necessary. After repairs, go to step 11 . If connections are okay, go to next step.
10. Replace PCM. After repairs, go to next step.
11. Using scan tool, clear DTCs. Test drive vehicle at speeds greater than 12 MPH. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0717 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related or TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTCs P0717, P0730, P0731, P0732 or P0734 are present, diagnose DTC P0717 first. Check for misrouted ISS sensor harness. Wiring may be near DIS components or ignition wires.

Note. TCC brake switch may also be known as TCC stoplight switch.

Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status to PCM. Normally open brake switch supplies voltage signal to PCM. Applying brake pedal closes switch, supplying voltage to PCM. Releasing brake pedal interrupts voltage to PCM.

Conditions For Setting DTC P0719

DTC will set under the following conditions

1. PCM detects an open brake switch (zero volts).

PCM performs the following if DTC is set

1. Does not illuminate MIL.
2. Stores DTC P0719 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Monitor TCC brake switch with scan tool. Disconnect TCC brake switch. Using test light connected to ground, probe cavity "B" (battery feed circuit) at TCC brake switch harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 3 .
2. While monitoring TCC brake switch status with scan tool, connect a fused jumper wire between terminals "A" and "B" at TCC brake switch harness connector. If status changes from OPEN to CLOSED, go to step 9 . If status does not change from OPEN to CLOSED, go to step 11 .
3. Remove STOP/HAZ fuse (20-amp) from instrument panel fuse block. Check for open fuse. If fuse is open, go to next step. If fuse is okay, go to step 11 .
4. Replace STOP/HAZ fuse. If fuse blows, go to next step. If fuse does not blow, go to step 6 .
5. Repair short to ground in TCC brake switch battery feed circuit. After repairs, go to step 14 .
6. Reconnect TCC brake switch. Apply brake pedal. If fuse blows, go to next step. If fuse does not blow, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
7. Disconnect Brown 24-pin PCM harness connector. Replace STOP/HAZ fuse. Apply brake pedal. If fuse blows, go to next step. If fuse does not blow, go to step 12 .
8. Repair short to ground in TCC brake switch input circuit. After repairs, go to step 14 .
9. Replace TCC brake switch. After repairs, go to step 14 .
10. Repair open in TCC brake switch battery feed circuit. After repairs, go to step 14 .
11. Check TCC brake switch input circuit for an open. If circuit is open, repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
12. Check for faulty PCM harness connections. If connections are faulty, repair as necessary. After repairs, go to step 14 . If connections are okay, go to next step.
13. Replace PCM. After repairs, go to next step.
14. Using scan tool, clear DTCs. With ignition on, apply brake pedal. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0719 is set, go to step 1 .

Check TCC brake switch for proper adjustment. Check PCM calibration for current update. Inspect wiring for poor connections at PCM and TCC brake switch. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 and P0730 are both present, diagnose DTC P0717 first. Check customer driving habits, such as stop-and-go traffic or freeway driving.

Transmission Output Shaft Speed (OSS) sensor circuit consists of a magnetic induction type sensor, Vehicle Speed Sensor (VSS) buffer module and wiring. Gear teeth pressed onto output shaft induce an alternating voltage into sensor. This signal transmits to VSS buffer module. VSS buffer module compensates for various final drive ratios. VSS buffer module also converts AC OSS sensor signal into a 40 pulse per revolution 5-volt DC signal to indicate transmission output speed.

Conditions For Setting DTC P0722

DTC will set under the following conditions

1. OSS sensor speed is less than 25 RPM for at least 3.5 seconds.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Defaults to maximum line pressure.
3. Defaults to a calculated output speed value using input speed sensor values.
4. Does not illuminate MIL.
5. Stores DTC P0722 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Raise and support vehicle. Start engine and place gear selector in "D1" position. While monitoring OSS sensor value, gradually increase wheel speed. If OSS sensor value increases with wheel speed, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If OSS sensor value does not increase with wheel speed, go to next step.
2. Turn ignition off. Disconnect OSS sensor. Using DVOM set to AC scale, connect leads to terminals of OSS sensor. Start engine and place gear selector in "D1" position. With wheels turning, slowly accelerate engine to 2000 RPM while monitoring DVOM. If AC voltage is greater than 2 volts, go to next step. If AC voltage is not greater than 2 volts, go to step 17 .
3. Reconnect OSS sensor. Disconnect VSS buffer module harness connector. Using DVOM set to AC scale, connect leads to terminals No. 7 (OSS sensor low circuit) and No. 12 (OSS sensor high circuit) at VSS buffer module harness connector. Start engine and place gear selector in "D1" position. With wheels turning, slowly accelerate engine to 2000 RPM while monitoring DVOM. If AC voltage is greater than 2 volts, go to step 6 . If AC voltage is not greater than 2 volts, go to next step.
4. Check for an open in OSS sensor high and low circuits. If circuit(s) is open, go to step 15 . If circuit(s) are okay, go to next step.
5. Check OSS sensor high and low circuits for a short to ground or short together. If circuits are shorted, go to step 15 . If circuits are okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
6. Using DVOM set to DC scale, measure voltage between ground and terminal No. 9 (ignition feed circuit) at VSS buffer module harness connector. If DC voltage is greater than 10.5 volts, go to step 8 . If DC voltage is not greater than 10.5 volts, go to next step.
7. Check VSS buffer module ignition feed circuit for an open or high resistance. If circuit is faulty, go to step 20 . If circuit is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
8. Using DVOM set to DC volts, measure voltage between terminals No. 8 (ground circuit) and No. 9 (ignition feed circuit) at VSS buffer module harness connector. If DC voltage is greater than 10.5 volts, go to step 10 . If DC voltage is not greater than 10.5 volts, go to next step.
9. Check for an open or high resistance in VSS buffer module ground circuit. If circuit is faulty, go to step 20 . If circuit is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
10. Using DVOM set to DC volts, measure voltage between ground and terminal No. 13 (OSS sensor signal input circuit) at VSS buffer module harness connector. If DC voltage is 4.8-5.2 volts, go to step 14 . If DC voltage is not 4.8-5.2 volts, go to next step.
11. If voltage measured in step 10 was greater than 5.2 volts, go to step 13 . If voltage measured in step 10 was not greater than 5.2 volts, go to next step.
12. Check OSS sensor signal input circuit for a short to ground. If circuit is shorted, go to step 20 . If circuit is okay, go to step 16 .
13. Check OSS sensor signal input circuit for a short to power. If circuit is shorted, go to step 20 . If circuit is okay, go to step 16 .
14. Reconnect VSS buffer module harness connector. Using DVOM set to DC volts, measure voltage (backprobe) between ground and terminal No. 13 (OSS sensor signal input circuit) at VSS buffer module harness connector. Start engine and place gear selector in "D1" position. With wheels rotating, slowly accelerate engine to 2000 RPM. If DC voltage is 1.5-3.5 volts, go to step 16 . If DC voltage is not 1.5-3.5 volts, go to step 18 .
15. Repair faulty circuits. After repairs, go to step 21 .
16. Check PCM harness connectors for faulty connections. If connections are faulty, go to step 20 . If connections are okay, go to step 19 .
17. Replace OSS sensor. After repairs, go to step 21 .
18. Replace VSS buffer module. After repairs, go to step 21 .
19. Replace PCM. After repairs, go to step 21 .
20. Repair faulty circuit(s) as necessary. After repairs, go to next step.
21. Using scan tool, clear DTCs. Test drive vehicle under steady acceleration. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0722 is set, go to step 1 .

Inspect wiring for poor connections at PCM, OSS sensor, VSS buffer module and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. 4WD vehicles use an in-line harness connector between OSS sensor harness and transfer case extension harness. Check speed sensor wiring for contact with sharp metal edges.

Transmission Output Shaft Speed (OSS) sensor circuit consists of a magnetic induction type sensor, Vehicle Speed Sensor (VSS) buffer module and wiring. Gear teeth pressed onto output shaft induce an alternating voltage into sensor. This signal transmits to VSS buffer module. VSS buffer module compensates for various final drive ratios. VSS buffer module also converts AC OSS sensor signal into a 40 pulse per revolution 5-volt DC signal to indicate transmission output speed.

Conditions For Setting DTC P0723

DTC will set under the following conditions

1. OSS RPM decreases more than 1000 RPM while in Drive for at least 3.5 seconds.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Defaults to maximum line pressure.
3. Defaults to a calculated output speed value using input speed sensor values.
4. Does not illuminate MIL.
5. Stores DTC P0723 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Raise and support vehicle. Start engine and place gear selector in "D1" position. While monitoring OSS sensor value, gradually increase wheel speed. If OSS sensor value increases with wheel speed, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If OSS sensor value does not increase with wheel speed, go to next step.
2. Turn ignition off. Disconnect OSS sensor. Using DVOM set to AC scale, connect leads to terminals of OSS sensor. Start engine and place gear selector in "D1" position. With wheels turning, slowly accelerate engine to 2000 RPM while monitoring DVOM. If AC voltage is greater than 2 volts, go to next step. If AC voltage is not greater than 2 volts, go to step 16 .
3. Reconnect OSS sensor. Disconnect VSS buffer module harness connector. Using DVOM set to AC scale, connect leads to terminals No. 7 (OSS sensor low circuit) and No. 12 (OSS sensor high circuit) at VSS buffer module harness connector. Start engine and place gear selector in "D1" position. With wheels turning, slowly accelerate engine to 2000 RPM while monitoring DVOM. If AC voltage is greater than 2 volts, go to step 6 . If AC voltage is not greater than 2 volts, go to next step.
4. Check for an intermittent open in OSS sensor high and low circuits. If circuit(s) is open, go to step 11 . If circuit(s) are okay, go to next step.
5. Check OSS sensor high and low circuits for an intermittent short to ground or short together. If circuits are shorted, go to step 11 . If circuits are okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
6. Using DVOM set to DC scale, measure voltage between ground and terminal No. 9 (ignition feed circuit) at VSS buffer module harness connector. If DC voltage is greater than 10.5 volts, go to step 8 . If DC voltage is not greater than 10.5 volts, go to next step.
7. Check VSS buffer module ignition feed circuit for an intermittent open or high resistance. If circuit is faulty, go to step 20 . If circuit is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
8. Using DVOM set to DC volts, measure voltage between terminals No. 8 (ground circuit) and No. 9 (ignition feed circuit) at VSS buffer module harness connector. If DC voltage is greater than 10.5 volts, go to step 10 . If DC voltage is not greater than 10.5 volts, go to next step.
9. Check for an open or high resistance in VSS buffer module ground circuit. If circuit is faulty, go to step 20 . If circuit is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
10. Using DVOM set to DC volts, measure voltage between ground and terminal No. 13 (OSS sensor signal input circuit) at VSS buffer module harness connector. If DC voltage is 4.8-5.2 volts, go to step 12 . If DC voltage is not 4.8-5.2 volts, go to step 13 .
11. Repair faulty circuits. After repairs, go to step 21 .
12. Reconnect VSS buffer module harness connector. Using DVOM set to DC volts, measure voltage (backprobe) between ground and terminal No. 13 (OSS sensor signal input circuit) at VSS buffer module harness connector. Start engine and place gear selector in "D1" position. With wheels rotating, slowly accelerate engine to 2000 RPM. If DC voltage is 1.5-3.5 volts, go to step 18 . If DC voltage is not 1.5-3.5 volts, go to step 17 .
13. If voltage measured in step 10 was greater than 5.2 volts, go to step 14 . If voltage measured in step 10 was not greater than 5.2 volts, go to step 15 .
14. Check OSS sensor signal input circuit for a short to power. If circuit is shorted, go to step 20 . If circuit is okay, go to step 19 .
15. Check OSS sensor signal input circuit for a short to ground. If circuit is shorted, go to step 20 . If circuit is okay, go to step 18 .
16. Replace OSS sensor. After repairs, go to step 21 .
17. Replace VSS buffer module. After repairs, go to step 21 .
18. Check PCM harness connectors for faulty connections. If connections are faulty, go to step 20 . If connections are okay, go to next step.
19. Replace PCM. After repairs, go to step 21 .
20. Repair faulty circuit(s) as necessary. After repairs, go to next step.
21. Using scan tool, clear DTCs. Test drive vehicle under steady acceleration. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0723 is set, go to step 1 .

Inspect wiring for poor connections at PCM, OSS sensor, VSS buffer module and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes.

Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status to PCM. Normally open brake switch supplies voltage signal to PCM. Applying brake pedal closes switch, supplying voltage to PCM. Releasing brake pedal interrupts voltage to PCM.

Conditions For Setting DTC P0724

DTC will set under the following conditions

1. TCC brake switch is closed for 15 minutes.

PCM performs the following if DTC is set

1. Does not illuminate MIL.
2. Stores DTC P0724 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. While monitoring TCC brake switch status on scan tool, disconnect TCC brake switch. If TCC brake switch status changed from CLOSED to OPEN, go to next step. If TCC brake switch status does not change from CLOSED to OPEN, go to step 3 .
2. Replace TCC brake switch. After repairs, go to step 6 .
3. Check TCC brake switch input circuit for a short to battery voltage. If circuit is shorted, go to step 5 . If circuit is okay, go to next step.
4. Replace PCM. After repairs, go to step 6 .
5. Repair faulty circuit as necessary. After repairs, go to next step.
6. Using scan tool, clear DTCs. Monitor TCC brake switch with scan tool while depressing brake pedal. If TCC brake switch status changes, system is okay. If TCC brake switch status does not change, go to step 1 .

Check TCC brake switch for proper adjustment. Check PCM calibration for current update. Inspect wiring for poor connections at PCM and at brake switch. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related or TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset.

PCM calculates gear ratio based on transmission input and output shaft speed sensor readings. PCM compares known transmission ratio calibration values to calculated ratios.

Conditions For Setting DTC P0730

DTC will set under the following conditions

1. PCM detects an incorrect gear ratio.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0730 in PCM history.

1. Ensure transmission fluid level is correct. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. While monitoring TFP switch A/B/C status on scan tool, apply parking brake and move gear selector through all ranges. If scan tool display corresponds to gear selector position, go to next step. If scan tool display does not correspond to gear selector position, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While monitoring scan tool, test drive vehicle in Reverse, 1st, 2nd, 3rd and 4th gears with vehicle speed greater than 5 MPH for more than 2 seconds in each specified gear. Using scan tool snapshot mode, record gear ratios for each commanded gear. Ensure gear ratios are within specification for each gear range. See «GEAR RATIO SPECIFICATIONS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) table. If gear ratios recorded with scan tool are within specifications, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If gear ratios recorded with scan tool are not within specifications, go to next step.
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, go to step 7 .
5. Remove transmission oil pan. Check for fluid contamination or debris. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for sticking shift valves or stuck apply pistons. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. After repairs, go to step 9 . If no problem is found, check for other internal malfunctions.
7. If line pressure was low only in gear range indicating an incorrect gear ratio, go to next step. If line pressure was low regardless of gear range, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Check for fluid pressure loss in the following areas: 1-2 and 2-3 shift solenoid seals. Valve body passages. Valve body gaskets. Band apply pistons and seals. Clutch apply pistons and seals. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, check for other internal malfunctions. See HYDRA-MATIC 4L80-E OVERHAUL article.
9. Using scan tool, clear DTCs. Test drive vehicle in all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0730 is set, go to step 1 .

GEAR RATIO SPECIFICATIONS

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. A false or incorrect input or OSS sensor signal can set DTC P0730. Ensure aftermarket equipment is installed properly. Sticking or contaminated shift solenoids may cause intermittent incorrect gear ratios. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 (input speed sensor) and DTC P0730 are both set, diagnose P0717 first.

PCM calculates gear ratio based on transmission input and output shaft speed sensor readings. PCM compares known transmission ratio calibration values to calculated ratios.

Conditions For Setting DTC P0731

DTC will set under the following conditions

1. PCM detects an incorrect gear ratio.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0731 in PCM history.

1. Ensure transmission fluid level is correct. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. While monitoring TFP switch A/B/C status on scan tool, apply parking brake and move gear selector through all ranges. If scan tool display corresponds to gear selector position, go to next step. If scan tool display does not correspond to gear selector position, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While monitoring scan tool, test drive vehicle in Drive ("D1" position). Hold vehicle in 1st gear for at least 2 seconds. Using scan tool snapshot mode, record gear ratio for 1st gear. If displayed gear ratio is 2.42-2.52, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If displayed gear ratio is not 2.42-2.52, go to next step.
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, go to step 7 .
5. Remove transmission oil pan. Check for fluid contamination or debris. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for sticking shift valves or stuck apply pistons. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. After repairs, go to step 9 . If no problem is found, check for other internal malfunctions.
7. If line pressure was low only in gear range indicating an incorrect gear ratio, go to next step. If line pressure was low regardless of gear range, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Check for fluid pressure loss in the following areas: 1-2 and 2-3 shift solenoid seals. Valve body passages. Valve body gaskets. Band apply pistons and seals. Clutch apply pistons and seals. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, check for other internal malfunctions. See HYDRA-MATIC 4L80-E OVERHAUL article.
9. Using scan tool, clear DTCs. Test drive vehicle in all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0731 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. A faulty 4WD front axle switch circuit may set DTC P0731. Ensure aftermarket equipment is installed properly. Sticking or contaminated shift solenoids may cause intermittent incorrect gear ratios. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 (input speed sensor) and DTC P0731 are both set, diagnose P0717 first.

PCM calculates gear ratio based on transmission input and output shaft speed sensor readings. PCM compares known transmission ratio calibration values to calculated ratios.

Conditions For Setting DTC P0732

DTC will set under the following conditions

1. PCM detects an incorrect gear ratio.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0732 in PCM history.

1. Ensure transmission fluid level is correct. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. While monitoring TFP switch A/B/C status on scan tool, apply parking brake and move gear selector through all ranges. If scan tool display corresponds to gear selector position, go to next step. If scan tool display does not correspond to gear selector position, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While monitoring scan tool, test drive vehicle in Drive ("D2" position). Hold vehicle in 2nd gear for at least 2 seconds. Using scan tool snapshot mode, record gear ratio for 2nd gear. If displayed gear ratio is 1.45-1.50, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If displayed gear ratio is not 1.45-1.50, go to next step.
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, go to step 7 .
5. Remove transmission oil pan. Check for fluid contamination or debris. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for sticking shift valves or stuck apply pistons. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. After repairs, go to step 9 . If no problem is found, check for other internal malfunctions.
7. If line pressure was low only in gear range indicating an incorrect gear ratio, go to next step. If line pressure was low regardless of gear range, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Check for fluid pressure loss in the following areas: 1-2 and 2-3 shift solenoid seals. Valve body passages. Valve body gaskets. Band apply pistons and seals. Clutch apply pistons and seals. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, check for other internal malfunctions. See HYDRA-MATIC 4L80-E OVERHAUL article.
9. Using scan tool, clear DTCs. Test drive vehicle in all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0732 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. A faulty 4WD front axle switch circuit may set DTC P0732. Ensure aftermarket equipment is installed properly. Sticking or contaminated shift solenoids may cause intermittent incorrect gear ratios. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 (input speed sensor) and DTC P0732 are both set, diagnose P0717 first.

PCM calculates gear ratio based on transmission input and output shaft speed sensor readings. PCM compares known transmission ratio calibration values to calculated ratios.

Conditions For Setting DTC P0733

DTC will set under the following conditions

1. PCM detects an incorrect gear ratio.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0733 in PCM history.

1. Ensure transmission fluid level is correct. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. While monitoring TFP switch A/B/C status on scan tool, apply parking brake and move gear selector through all ranges. If scan tool display corresponds to gear selector position, go to next step. If scan tool display does not correspond to gear selector position, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While monitoring scan tool, test drive vehicle in Drive ("D3" position). Hold vehicle in 3rd gear for at least 2 seconds. Using scan tool snapshot mode, record gear ratio for 3rd gear. If displayed gear ratio is .98-1.02, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If displayed gear ratio is not .98-1.02, go to next step.
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, go to step 7 .
5. Remove transmission oil pan. Check for fluid contamination or debris. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for sticking shift valves or stuck apply pistons. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. After repairs, go to step 9 . If no problem is found, check for other internal malfunctions.
7. If line pressure was low only in gear range indicating an incorrect gear ratio, go to next step. If line pressure was low regardless of gear range, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Check for fluid pressure loss in the following areas: 1-2 and 2-3 shift solenoid seals. Valve body passages. Valve body gaskets. Band apply pistons and seals. Clutch apply pistons and seals. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, check for other internal malfunctions. See HYDRA-MATIC 4L80-E OVERHAUL article.
9. Using scan tool, clear DTCs. Test drive vehicle in all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0733 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. A faulty 4WD front axle switch circuit may set DTC P0733. Ensure aftermarket equipment is installed properly. Sticking or contaminated shift solenoids may cause intermittent incorrect gear ratios. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 (input speed sensor) and DTC P0733 are both set, diagnose P0717 first.

PCM calculates gear ratio based on transmission input and output shaft speed sensor readings. PCM compares known transmission ratio calibration values to calculated ratios.

DTC will set under the following conditions

1. PCM detects an incorrect gear ratio.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0734 in PCM history.

1. Ensure transmission fluid level is correct. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. While monitoring TFP switch A/B/C status on scan tool, apply parking brake and move gear selector through all ranges. If scan tool display corresponds to gear selector position, go to next step. If scan tool display does not correspond to gear selector position, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While monitoring scan tool, test drive vehicle in Drive ("D4" position). Hold vehicle in 4th gear for at least 2 seconds. Using scan tool snapshot mode, record gear ratio for 4th gear. If displayed gear ratio is .73-.77, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If displayed gear ratio is not .73-.77, go to next step.
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, go to step 7 .
5. Remove transmission oil pan. Check for fluid contamination or debris. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for sticking shift valves or stuck apply pistons. If a problem is found, repair as necessary. See HYDRA-MATIC 4L80-E OVERHAUL article. After repairs, go to step 9 . If no problem is found, check for other internal malfunctions.
7. If line pressure was low only in gear range indicating an incorrect gear ratio, go to next step. If line pressure was low regardless of gear range, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Check for fluid pressure loss in the following areas: 1-2 and 2-3 shift solenoid seals. Valve body passages. Valve body gaskets. Band apply pistons and seals. Clutch apply pistons and seals. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, check for other internal malfunctions. See HYDRA-MATIC 4L80-E OVERHAUL article.
9. Using scan tool, clear DTCs. Test drive vehicle in all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0734 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. A faulty 4WD front axle switch circuit may set DTC P0734. Ensure aftermarket equipment is installed properly. Sticking or contaminated shift solenoids may cause intermittent incorrect gear ratios. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. If DTC P0717 (input speed sensor) and DTC P0734 are both set, diagnose P0717 first.

DTC P0741: TCC SYSTEM - STUCK OFF

Note. For oil circuit identification, see appropriate oil circuit diagram in OIL CIRCUIT DIAGRAMS. DTC P0741 inspects for high TCC slip in 2nd and 3rd gear only. Transmission must be in hot mode or experiencing a wide open throttle maneuver in order for TCC apply to occur in 2nd and 3rd gear.

PCM commands Torque Converter Clutch (TCC) Pulse Width Modulated (PWM) solenoid on and off through ground circuit. When PCM grounds (energizes) TCC PWM solenoid, solenoid stops converter signal oil exhaust. This causes converter signal oil pressure to increase and shift TCC valve. When TCC PWM solenoid is de-energized, solenoid will exhaust fluid and release TCC.

Conditions For Setting DTC P0741

DTC will set under the following conditions

1. PCM detects high torque converter slip speed with TCC commanded on.

PCM performs the following if DTC is set

1. Does not illuminate MIL.
2. Increases line pressure.
3. Inhibits TCC engagement and 4th gear.
4. Stores DTC P0741 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Test drive vehicle in "D3" position with TCC commanded on. Using scan tool, record snapshot data. If TCC slip speed is greater than 175 RPM when TCC PWM solenoid is commanded on by more than 70 percent, go to next step. If TCC slip speed is not greater than 175 RPM when TCC PWM solenoid is commanded on by more than 70 percent, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Check TCC PWM solenoid for mechanical failure. Solenoid may be mechanically stuck off. Repair as necessary. After repairs, go to step 4 . If solenoid is mechanically okay, go to next step.
3. Check for torque converter clutch for mechanical failure. TCC may be mechanically stuck off. Check for damaged or clogged TCC exhaust orifice, converter clutch apply valve stuck in released position, misaligned or damaged valve body gasket, or a restricted apply or release passage. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle in "D4" position under steady acceleration. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0741 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related or TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. Residue or contamination may cause shift solenoids to stick intermittently.

DTC P0742: TCC SYSTEM - STUCK ON

Note. For oil circuit identification, see appropriate oil circuit diagram in OIL CIRCUIT DIAGRAMS.

PCM commands Torque Converter Clutch (TCC) Pulse Width Modulated (PWM) solenoid on and off through ground circuit. When PCM grounds (energizes) TCC PWM solenoid, solenoid stops converter signal oil exhaust. This causes converter signal oil pressure to increase and shift TCC valve. When TCC PWM solenoid is de-energized, solenoid will exhaust fluid and release TCC

Conditions For Setting DTC P0742

DTC will set under the following conditions

1. PCM detects low torque converter slip speed with TCC commanded off.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Does not illuminate MIL.
4. Stores DTC P0742 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Using scan tool, verify APP sensor operation. If APP sensor angle is zero percent at closed throttle and 100 percent at wide open throttle, go to next step. If APP sensor values are not as specified, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. While monitoring TCC slip speed with scan tool, test drive vehicle in 4th gear ("D4" position) under steady acceleration with APP sensor angle greater than 15 percent. If TCC slip speed is -10-10 RPM with TCC duty cycle at zero percent, go to next step. If TCC slip speed is not -10-10 RPM with TCC duty cycle at zero percent, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. TCC is mechanically stuck on. Check for clogged TCC PWM solenoid exhaust orifice, stuck TCC shift valve, misaligned or damaged valve body gasket, restricted apply or release passages, or restricted transmission cooler lines. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle in 4th gear ("D4" position) with TCC duty cycle at zero percent and APP sensor angle greater than 15 percent. Ensure TCC slip speed is 175-1500 RPM for 3 seconds. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0742 is set, go to step 1 .

TCC may mechanically stick on with parking brake applied and any gear range selected. TCC fluid will mechanically apply TCC, which may cause engine to stall. A stuck TP sensor will set DTC P0742. First diagnose and clear any engine-related or TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset.

Pressure Control (PC) solenoid is used to regulate transmission line pressure. PCM compares TP sensor voltage, engine RPM and other inputs to determine appropriate line pressure for given load. PCM will regulate pressure by applying varying amperage to PC solenoid. Applied amperage can vary from .1 to 1.1 amps. PCM monitors circuit amperage.

Conditions For Setting DTC P0748

DTC will set under the following conditions

1. PCM detects a continuous open or short to ground condition in PC solenoid circuit.

PCM performs the following if DTC is set

1. Disables PC solenoid and defaults transmission to maximum line pressure.
2. Freezes shift adapts from being updated.
3. Does not illuminate MIL.
4. Stores DTC P0748 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine. Using scan tool output control function, apply .1-1.0 amp while monitoring PC REF. CURRENT and PC ACT. CURRENT. If PC ACT. CURRENT is always within .16 amp of PC REF. CURRENT, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If PC ACT. CURRENT is not always within .16 amp of PC REF. CURRENT, go to next step.
2. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39885) to transmission side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "C" and "D" of jumper harness. If resistance is 3-7 ohms, go to step 5 . If resistance is not 3-7 ohms, go to next step.
3. Disconnect transmission wire harness assembly from PC solenoid valve. Measure resistance of PC solenoid valve. If resistance is 3-7 ohms, go to next step. If resistance is not 3-7 ohms, go to step 7 .
4. Replace transmission wire harness assembly. After repairs, go to step 16 .
5. Measure resistance between transmission case and terminal "C" of jumper harness. If resistance is less than 7 ohms, go to next step. If resistance is not less than 7 ohms, go to step 8 .
6. Check PC solenoid valve high and low circuits for a short to ground. If circuit(s) is shorted, go to step 15 . If circuit(s) are okay, go to next step.
7. Replace PC solenoid valve. After repairs, go to step 16 .
8. Remove jumper harness and reconnect 20-pin transmission harness connector. Disconnect Brown 32-pin PCM harness connector. Measure resistance between terminals C7 (PC solenoid valve high circuit) and C15 (PC solenoid valve low circuit) at PCM harness connector. If resistance is 3-7 ohms, go to next step. If resistance is not 3-7 ohms, go to step 10 .
9. Measure resistance between ground and terminal C7 (PC solenoid valve high circuit). If resistance is greater than 7 ohms, go to step 14 . If resistance is not greater than 7 ohms, go to step 13 .
10. If resistance measured in step 8 was greater than 7 ohms, go to next step. If resistance measured in step 8 was not greater than 7 ohms, go to step 12 .
11. Check PC solenoid valve circuits for an open. If circuit(s) is open, go to step 15 . If circuit(s) is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
12. Check PC solenoid valve circuits for short together. If circuits are shorted, go to step 15 . If circuits are okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
13. Check PC solenoid valve circuits for short to ground. If circuit(s) is shorted, go to step 15 . If circuit(s) is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
14. Replace PCM. After repairs, go to step 16 .
15. Repair faulty circuit(s) as necessary. After repairs, go to next step.
16. Using scan tool, clear DTCs. Start engine. Ensure PC solenoid valve duty cycle is 2-95 percent. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0748 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. Inspect for improperly wired after market equipment. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset.

The 1-2 shift solenoid valve is used to control fluid flow acting on 1-2 and 3-4 shift valves. Solenoid is a normally open exhaust valve that is used in conjunction with 2-3 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0751

DTC will set under the following conditions

1. First gear is commanded with a gear ratio equal to second gear.
2. Fourth gear is commanded and TCC applied with a gear ratio equal to third gear.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Illuminates MIL.
4. Stores DTC P0751 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and let idle. Apply parking brake. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds to scan tool display, go to next step. If gear range does not correspond to scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Raise and support vehicle. Start engine. Place gear selector in "D4" position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If a 1-1-4-4 or 2-2-3-3 shift pattern is detected, go to next step. If a 1-1-4-4 or 2-2-3-3 shift pattern is not detected, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Check 1-2 or 3-4 shift solenoid valve for an internal malfunction. Check shift solenoid valve hydraulic circuits for damaged seals. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle through all gear ranges. With gear selector in "D4" position, accelerate vehicle to 55 MPH. Using scan tool, check for DTCs. If no DTCs are present, system is okay. If DTC P0751 is set, go to step 1 .

Verify shift speeds are correct. See HYDRA-MATIC 4L80-E OVERHAUL article. More than one shift may occur due to other internal transmission failures. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset.

The 1-2 shift solenoid valve is used to control fluid flow acting on 1-2 and 3-4 shift valves. Solenoid is a normally open exhaust valve that is used in conjunction with 2-3 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0752

DTC will set under the following conditions

1. Second gear is commanded with a gear ratio equal to first gear.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Illuminates MIL.
4. Stores DTC P0752 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and let idle. Apply parking brake. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds to scan tool display, go to next step. If gear range does not correspond to scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Raise and support vehicle. Start engine. Place gear selector in "D4" position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If a 1-1-4-4 or 2-2-3-3 shift pattern is detected, go to next step. If a 1-1-4-4 or 2-2-3-3 shift pattern is not detected, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Check 1-2 or 3-4 shift solenoid valve for an internal malfunction. Check shift solenoid valve hydraulic circuits for damaged seals. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle through all gear ranges. With gear selector in "D4" position, accelerate vehicle to 55 MPH. Using scan tool, check for DTCs. If no DTCs are present, system is okay. If DTC P0752 is set, go to step 1 .

Verify shift speeds are correct. See HYDRA-MATIC 4L80-E OVERHAUL article. More than one shift may occur due to other internal transmission failures. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset.

The 1-2 shift solenoid valve is used to control fluid flow acting on 1-2 and 3-4 shift valves. Solenoid is a normally open exhaust valve that is used in conjunction with 2-3 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0753

DTC will set under the following conditions

1. PCM commands solenoid on and voltage remains high (battery voltage).
2. PCM commands solenoid off and voltage remains low (zero volts).

PCM performs the following if DTC is set

1. Illuminates MIL.
2. Freezes shift adapts from being updated.
3. Commands to maximum line pressure.
4. Stores DTC P0753 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. If DTCs P0758 or P1860 also set, go to next step. If DTCs P0758 and P1860 are not set, go to step 3 .
2. Check for open TRANS fuse (10-amp) located in instrument panel fuse block. If fuse is open, check solenoid ignition feed circuit, transmission solenoids and transmission wire harness assembly for a short to ground. If a short is found, repair circuit as necessary. After repairs, go to step 15 . If no shorts are found, go to step 4 .
3. Using scan tool output control function, command 1-2 shift solenoid valve on and off 3 times while listening to bottom of transmission oil pan. If solenoid clicks when commanded, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If solenoid does not click when commanded, go to next step.
4. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39775) to engine side of 20-pin transmission harness connector. Turn ignition on. Using test light connected to ground, probe cavity "E" (ignition feed circuit) at jumper harness. If test light illuminates, go to step 6 . If test light does not illuminate, go to next step.
5. Repair open or short to ground in ignition feed circuit. After repairs, go to step 15 .
6. Connect test light between terminals "A" (1-2 shift solenoid valve control circuit) and "E" (ignition feed circuit) at jumper harness. Using scan tool output control function, command 1-2 shift solenoid valve on and off 3 times. If test light illuminates as solenoid is commanded, go to step 9 . If test light does not illuminate as solenoid is commanded, go to next step.
7. Check 1-2 shift solenoid valve control circuit for an open or short to ground. If circuit is faulty, repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
8. Replace PCM. After repairs, go to step 15 .
9. Turn ignition off. Connect Jumper Harness (J-39775) to transmission side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "A" and "E" at transmission side of 20-pin transmission harness connector. If resistance is 19-31 ohms, go to step 11 . If resistance is not 19-31 ohms, go to next step.
10. Disconnect transmission wire harness assembly from 1-2 shift solenoid valve. Measure resistance of 1-2 shift solenoid valve. If resistance is 19-31 ohms, go to step 13 . If resistance is not 19-31 ohms, go to step 14 .
11. Measure resistance between ground and terminal "A", and then between ground and terminal "E" of transmission side of 20-pin transmission harness connector. If resistance is greater than 250 k/ohms, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If resistance is not greater than 250 k/ohms, go to next step.
12. Disconnect transmission wire harness assembly from 1-2 shift solenoid valve. Measure resistance between ground and terminals of 1-2 shift solenoid valve. If resistance is greater than 250 k/ohms, go to next step. If resistance is not greater than 250 k/ohms, go to step 14 .
13. Replace transmission wire harness assembly. After repairs, go to step 15 .
14. Replace 1-2 shift solenoid valve. After repairs, go to next step.
15. Using scan tool, clear DTCs. Test drive vehicle. Ensure transmission shifts through all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0753 is set, go to step 1 .

Inspect wiring for poor connections at PCM. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset. An open ignition feed circuit can cause multiple DTCs to set.

The 2-3 shift solenoid valve is used to control fluid flow acting on 2-3 shift valve. Solenoid is a normally open exhaust valve that is used in conjunction with 1-2 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0756

DTC will set under the following conditions

1. PCM detects a gear ratio equal to 4th gear with 1st gear commanded.
2. PCM detects a gear ratio equal to 3rd gear with 2nd gear commanded.

PCM performs the following if DTC is set

1. Commands 2nd gear.
2. Commands maximum line pressure.
3. Freezes shift adapts from being updated.
4. Illuminates MIL.
5. Stores DTC P0756 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and let idle. Apply parking brake. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds to scan tool display, go to next step. If gear range does not correspond to scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Raise and support vehicle. Start engine. Place gear selector in "D4" position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If a 4-3-3-4 shift pattern is detected, go to next step. If a 4-3-3-4 shift pattern is not detected, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Check shift solenoid valves for an internal malfunction. Check shift solenoid valve hydraulic circuits for damaged seals. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle through all gear ranges. With gear selector in "D4" position, accelerate vehicle to 55 MPH. Using scan tool, check for DTCs. If no DTCs are present, system is okay. If DTC P0756 is set, go to step 1 .

Verify shift speeds are correct. See HYDRA-MATIC 4L80-E OVERHAUL article. More than one shift may occur due to other internal transmission failures. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset. Customer may complain of an engine over-rev condition or Neutral condition in 4th gear.

The 2-3 shift solenoid valve is used to control fluid flow acting on 2-3 shift valve. Solenoid is a normally open exhaust valve that is used in conjunction with 1-2 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0757

DTC will set under the following conditions

1. PCM detects a gear ratio equal to 2nd gear with 3rd gear commanded.

PCM performs the following if DTC is set

1. Commands 2nd gear.
2. Commands maximum line pressure.
3. Freezes shift adapts from being updated.
4. Illuminates MIL.
5. Stores DTC P0757 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and let idle. Apply parking brake. While monitoring TFP switch A/B/C parameter on scan tool, move gear selector through all gear ranges. If gear range corresponds to scan tool display, go to next step. If gear range does not correspond to scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Raise and support vehicle. Start engine. Place gear selector in "D4" position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If a 1-2-2-1 shift pattern is detected, go to next step. If a 1-2-2-1 shift pattern is not detected, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Check shift solenoid valves for an internal malfunction. Check shift solenoid valve hydraulic circuits for damaged seals. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Using scan tool, clear DTCs. Test drive vehicle through all gear ranges. With gear selector in "D4" position, accelerate vehicle to 55 MPH. Using scan tool, check for DTCs. If no DTCs are present, system is okay. If DTC P0757 is set, go to step 1 .

Verify shift speeds are correct. See HYDRA-MATIC 4L80-E OVERHAUL article. More than one shift may occur due to other internal transmission failures. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset. Customer may complain of an engine over-rev condition or Neutral condition in 4th gear.

The 2-3 shift solenoid valve is used to control fluid flow acting on 2-3 shift valve. Solenoid is a normally open exhaust valve that is used in conjunction with 1-2 shift solenoid valve to allow 4 different shifting combinations. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit.

Conditions For Setting DTC P0758

DTC will set under the following conditions

1. PCM commands solenoid on and voltage remains high (battery voltage).
2. PCM commands solenoid off and voltage remains low (zero volts).

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Commands 2nd gear.
4. Illuminates MIL.
5. Stores DTC P0758 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. If DTCs P0753 or P1860 also set, go to next step. If DTCs P0753 and P1860 are not set, go to step 3 .
2. Check for open TRANS fuse (10-amp) located in instrument panel fuse block. If fuse is open, check solenoid ignition feed circuit, transmission solenoids and transmission wire harness assembly for a short to ground. If a short is found, repair circuit as necessary. After repairs, go to step 15 . If no shorts are found, go to step 4 .
3. Using scan tool output control function, command 2-3 shift solenoid valve on and off 3 times while listening to bottom of transmission oil pan. If solenoid clicks when commanded, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If solenoid does not click when commanded, go to next step.
4. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39775) to engine side of 20-pin transmission harness connector. Turn ignition on. Using test light connected to ground, probe cavity "E" (ignition feed circuit) at jumper harness. If test light illuminates, go to step 6 . If test light does not illuminate, go to next step.
5. Repair open or short to ground in ignition feed circuit. After repairs, go to step 15 .
6. Connect test light between terminals "B" (2-3 shift solenoid valve control circuit) and "E" (ignition feed circuit) at jumper harness. Using scan tool output control function, command 2-3 shift solenoid valve on and off 3 times. If test light illuminates as solenoid is commanded, go to step 9 . If test light does not illuminate as solenoid is commanded, go to next step.
7. Check 2-3 shift solenoid valve control circuit for an open or short to ground. If circuit is faulty, repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
8. Replace PCM. After repairs, go to step 15 .
9. Turn ignition off. Connect Jumper Harness (J-39775) to transmission side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "B" and "E" at transmission side of 20-pin transmission harness connector. If resistance is 19-31 ohms, go to step 11 . If resistance is not 19-31 ohms, go to next step.
10. Disconnect transmission wire harness assembly from 2-3 shift solenoid valve. Measure resistance of 2-3 shift solenoid valve. If resistance is 19-31 ohms, go to step 13 . If resistance is not 19-31 ohms, go to step 14 .
11. Measure resistance between ground and terminal "B", and then between ground and terminal "E" of transmission side of 20-pin transmission harness connector. If resistance is greater than 250 k/ohms, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If resistance is not greater than 250 k/ohms, go to next step.
12. Disconnect transmission wire harness assembly from 2-3 shift solenoid valve. Measure resistance between ground and terminals of 2-3 shift solenoid valve. If resistance is greater than 250 k/ohms, go to next step. If resistance is not greater than 250 k/ohms, go to step 14 .
13. Replace transmission wire harness assembly. After repairs, go to step 15 .
14. Replace 2-3 shift solenoid valve. After repairs, go to next step.
15. Using scan tool, clear DTCs. Test drive vehicle. Ensure transmission shifts through all gear ranges. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P0758 is set, go to step 1 .

Inspect wiring for poor connections at PCM. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs, and then inspect for any transmission-related DTCs that may have reset.

Transmission Fluid Pressure (TFP) position switch assembly consists of 5 normally-open pressure switches. Complete assembly mounts on control valve body. PCM supplies battery voltage to each range switch. PCM grounds one or more range switch signal circuits through various combinations of pressure switches. PCM monitors combinations in order to detect what manual valve position has been selected. PCM compares actual voltage combination of switches to TFP position switch combination values stored in memory. TFP position switch cannot distinguish between Park and Neutral because monitored valve body pressures are identical.

Conditions For Setting DTC P1810

DTC will set under the following conditions

1. PCM detects an illegal TFP manual valve position switch state. See «TFP LOGIC»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) table.
2. PCM detects gear range as "D2" before and after start-up.
3. PCM detects incorrect gear ratio for selected gear range.

TFP LOGIC

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Commands maximum line pressure.
3. Defaults shift pattern to "D4".
4. Illuminates MIL.
5. Stores DTC P1810 in PCM history.

1. Check transmission fluid level. Fill if necessary. Ensure transmission shift linkage is adjusted correctly, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and the clear DTCs. Start engine and allow it to reach normal operating temperature. Apply parking brake. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds with scan tool display, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If gear range does not correspond with scan tool display, go to next step.
3. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39775) to engine side of 20-pin transmission harness connector. Turn ignition on. Using DVOM and Connector Test Adapter Kit (J-35616), measure voltage between ground and terminals "N", "R" and "P" (input circuits) at engine side of 20-pin transmission harness connector. If battery voltage is present, go to step 5 . If battery voltage is not present, go to next step.
4. Check circuit(s) that did not indicate battery voltage in step 3 for an open or short to ground. If circuit(s) is open or shorted, go to step 7 . If circuit(s) is okay, go to step 6 .
5. Check input circuits for a short together by grounding each circuit and monitoring scan tool display. If circuits are shorted together, multiple range circuits will be affected on scan tool. If circuits are shorted together, go to step 7 . If circuits are okay, check TFP manual valve position switch resistance. See «TFP MANUAL VALVE POSITION SWITCH & WIRE HARNESS RESISTANCE CHECKS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes__tfp-manual-valve-position-switch) under COMPONENT TESTS. Repair as necessary. After repairs, go to step 8 .
6. Replace PCM. After repairs, go to step 8 .
7. Repair faulty circuit as necessary. After repairs, go to next step.
8. Using scan tool, clear DTCs. Test drive vehicle in "D4" position and obtain TCC lock-up. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P1810 is set, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Inspect for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. DTC P1810 can be falsely set during fluid fill procedure. After refilling fluid, cycle key off, and then start and run engine for 20 seconds. Turn ignition off and allow PCM to power down, and then restart vehicle. DTC P1810 can be falsely set by low pump pressure or a stuck pressure regulator. DTC P1810 can be set by a slipping forward clutch assembly. PCM may see a 2.08:1 ratio (Reverse) when manual valve position is "D4".

PCM compares measured gear ratio to known actual value. This allows PCM to determine actual gear range of transmission. When an upshift is commanded, PCM measures interval during which gear ratio leaves current range and changes to reflect commanded upshift. This interval is displayed on scan tool as "Shift Time". When this interval has exceeded a predetermined limit, PCM utilizes shift adapts in order to attempt to shorten shift time.

Conditions For Setting DTC P1811

DTC will set under the following conditions

1. The 1-2 or 2-3 upshifts are more than 1.25 seconds.
2. The 3-4 upshift is more than 6.37 seconds.

PCM performs the following if DTC is set

1. Commands maximum line pressure.
2. Does not illuminate MIL.
3. Stores DTC P1811 in PCM history.

1. Check transmission fluid level. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and apply brake pedal. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds with scan tool display, go to next step. If gear range does not correspond with scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. While using scan tool in snapshot mode, test drive vehicle in "D4" position to obtain a 1-2, 2-3 and 3-4 shift and record shift times. If shift times are greater than 1.25 seconds for 1-2 and 2-3 shifts, and greater than 6.37 seconds for 3-4 shift, go to next step. If shift times are not as specified, go to step 7 .
4. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, diagnose cause for low line pressure. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article.
5. Remove transmission oil pan. Check fluid for contamination and debris. If a problem is found, repair transmission internal malfunction. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
6. Check for fluid pressure loss at valve body gasket, forward clutch seals and turbine shaft seals. Repair as necessary. After repairs, go to step 14 . If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
7. Select 1-2, 2-3 and 3-4 Transmission Adaptive Pressure (TAP) cells on scan tool. If any upshift TAP cells are greater than 16 psi (1.1 kg/cm 2 ), go to next step. If no upshift TAP cells are greater than 16 psi (1.1 kg/cm 2 ), see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
8. If 3-4 shift time exceeded 6.37 seconds, go to step 11 . If 3-4 shift time did not exceed 6.37 seconds, go to next step.
9. If 2-3 shift time exceeded 1.25 seconds, go to step 12 . If 2-3 shift time did not exceed 1.25 seconds, go to next step.
10. If 1-2 shift time exceeded 1.25 seconds, go to step 14 . If 1-2 shift time did not exceed 1.25 seconds, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
11. Check 4th gear clutch plates and clutch seals. Check for sticking 3-4 shift valve. See HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary. After repairs, go to step 14 . If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
12. Check turbine shaft seals, forward clutch plates and clutch seals, direct clutch plates and clutch seals and center support seals. Check for improperly tightened center support bolt. Repair as necessary. After repairs, go to step 14 . If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
13. Check low roller clutch, intermediate clutch plates, seals and sprag and overdrive roller clutch. Check for improperly tightened center support bolt. Repair as necessary. After repairs, go to next step. If no problem is found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
14. Using scan tool, clear DTCs. Test drive vehicle in "D4" position to obtain several 1-2-3-4 upshifts. Record shift times with scan tool. If shift times are less than 1.25 seconds for 1-2 and 2-3 shifts, and less than 6.37 seconds for 3-4 shift, system is okay. If shift times are not as specified, go to step 1 .

Inspect wiring for poor connections at PCM and at 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. DTC P1811 can be caused by a faulty turbocharger or wastegate assembly. Check and repair as necessary. While driving vehicle, inspect for loss of power, misfire or other engine-related driving problems. If after several unsuccessful attempts to gain accurate shift times, and an adapt can be made, reset adapts and operate vehicle to ensure proper shifting. Ask customer about overloading vehicle, exceeding towing limit or towing in overdrive.

TCC PWM solenoid is used to control fluid flow acting on TCC valve. Solenoid controls TCC apply and release. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. Current flows through TCC PWM solenoid coil according to duty cycle (percentage of on and off time). TCC PWM solenoid provides a smooth engagement of TCC by operating during duty cycle percent of on time.

Conditions For Setting DTC P1860

DTC will set under the following conditions

1. PCM commands solenoid off and voltage remains low (zero volts).
2. PCM commands solenoid on and voltage remains high (battery voltage).

PCM performs the following if DTC is set

1. Illuminates MIL.
2. Inhibits TCC engagement.
3. Inhibits 4th gear.
4. Freezes shift adapts from being updated.
5. Stores DTC P1860 in PCM history.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Check for open TRANS fuse (10-amp) located in instrument panel fuse block. If fuse is open, go to next step. If fuse is okay, go to step 3 .
2. Check for open TRANS fuse (10-amp) located in instrument panel fuse block. If fuse is open, check solenoid ignition feed circuit, transmission solenoids and transmission wire harness assembly for a short to ground. If a short is found, repair as necessary. After repairs, go to step 16 . If no shorts are found, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Turn ignition off. Disconnect 20-pin transmission harness connector. Connect Jumper Harness (J-39775) to engine side of 20-pin transmission harness connector. Turn ignition on. Using test light connected to ground, probe cavity "E" (ignition feed circuit) at jumper harness. If test light illuminates, go to step 5 . If test light does not illuminate, go to next step.
4. Repair open or high resistance in ignition feed circuit. After repairs, go to step 16 .
5. Connect test light between terminals "S" (TCC PWM solenoid valve control circuit) and "E" (ignition feed circuit) at jumper harness. Using scan tool output control function, command TCC PWM solenoid valve on and off 3 times. If test light illuminates as solenoid is commanded, go to step 7 . If test light does not illuminate as solenoid is commanded, go to next step.
6. Check TCC PWM solenoid valve control circuit for an open or short to ground. If circuit is faulty, repair as necessary. After repairs, go to step 16 . If circuit is okay, go to step 8 .
7. Turn ignition off. Connect Jumper Harness (J-39775) to transmission side of 20-pin transmission harness connector. Using DVOM and Connector Test Adapter Kit (J-35616), measure resistance between terminals "S" and "E" at transmission side of 20-pin transmission harness connector. If resistance is 10-15 ohms, go to step 10 . If resistance is not 10-15 ohms, go to step 9 .
8. Replace PCM. After repairs, go to step 16 .
9. Disconnect transmission wire harness assembly from TCC PWM solenoid valve. Measure resistance of TCC PWM solenoid valve. If resistance is 10-15 ohms, go to step 11 . If resistance is not 10-15 ohms, go to step 14 .
10. Measure resistance between ground and terminal "S", and then between ground and terminal "E" of transmission side of 20-pin transmission harness connector. If resistance is greater than 250 k/ohms, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) . If resistance is not greater than 250 k/ohms, go to step 12 .
11. Check transmission wire assembly for an open circuit. If an open is found, go to step 15 . If wire harness is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
12. Disconnect transmission wire harness assembly from TCC PWM solenoid valve. Measure resistance between ground and terminals of TCC PWM solenoid valve. If resistance is greater than 250 k/ohms, go to next step. If resistance is not greater than 250 k/ohms, go to step 14 .
13. Check transmission wire harness assembly for a short to ground. If wire harness is shorted, go to step 15 . If wire harness is okay, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
14. Replace TCC PWM solenoid valve. After repairs, go to step 16 .
15. Replace transmission wire harness assembly. After repairs, go to next step.
16. Using scan tool, clear DTCs. Test drive vehicle. Ensure transmission shifts through all gear ranges and TCC engages and disengages. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P1860 is set, go to step 1 .

Inspect wiring for poor connections at PCM and 20-pin transmission harness connector. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset.

PCM monitors difference between engine speed and transmission output speed. PCM calculates turbine shaft speed and TCC slip speed by utilizing inputs from input speed sensor, output shaft speed sensor and other transmission components. In "D3" position with TCC engaged, engine speed should closely match transmission output speed. In "D4" position with TCC engaged, TCC slip speed should be -25 to 30 RPM.

Conditions For Setting DTC P1870

DTC will set under the following conditions

1. PCM detects an excessive slip speed in "D4" position when TCC should be engaged.

PCM performs the following if DTC is set

1. Inhibits TCC engagement.
2. Inhibits 4th gear if in hot mode.
3. Freezes shift adapts from being updated.
4. Commands maximum line pressure.
5. Illuminates MIL.
6. Stores DTC P1870 in PCM history.

1. Check transmission fluid level. Fill if necessary, and then go to next step.
2. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Start engine and allow it to reach normal operating temperature. Apply brake pedal. While monitoring TFP switch A/B/C status on scan tool, move gear selector through all gear ranges. If gear range corresponds with scan tool display, go to next step. If gear range does not correspond with scan tool display, diagnose using diagnostic procedure for DTC P1810. See «DTC P1810: TFP MANUAL VALVE POSITION SWITCH - INVALID RANGE»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
3. Test drive vehicle in "D4" position under normal operating temperature with TCC duty cycle greater than 70 percent. Using scan tool, monitor TCC slip speed. If TCC slip speed is greater than 120 RPM for 6 seconds, go to next step. If TCC slip speed is not greater than 120 RPM for 6 seconds, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
4. Test drive vehicle in "D3" position. Using scan tool, command TCC on. If TCC slip speed is greater than 110 RPM for 6 seconds, go to step 6 . If TCC slip speed is not 110 RPM for 6 seconds, go to next step.
5. Repeat procedure in step 3 . If TCC slip speed is greater than 120 RPM, go to step 7 . If TCC slip speed is not greater than 120 RPM for 6 seconds, go to step 10 .
6. Diagnose by symptom. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary. After repairs, go to step 11 .
7. Check line pressure. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS in HYDRA-MATIC 4L80-E OVERHAUL article. If line pressure is within specifications, go to next step. If line pressure is not within specifications, diagnose by symptom. See SYMPTOM DIAGNOSIS under TROUBLE SHOOTING in HYDRA-MATIC 4L80-E OVERHAUL article. Repair as necessary.
8. Remove transmission oil pan. Check fluid for contamination and debris. If fluid is contaminated, repair internal transmission malfunction. See HYDRA-MATIC 4L80-E OVERHAUL article. If fluid is okay, go to next step.
9. Check 1-2 and 2-3 shift solenoid valve for contamination or damaged seals. If a problem is found, repair as necessary. After repairs, go to step 11 . If no problem is found, go to next step.
10. Check 2-3 and 3-4 shift valves for contamination or sticking. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, repair internal transmission malfunction. See HYDRA-MATIC 4L80-E OVERHAUL article.
11. Using scan tool, clear DTCs. Test drive vehicle in "D4" position and obtain TCC lock-up. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P1870 is set, go to step 1 .

A TFP position switch (Pressure Switch Assembly) malfunction could set DTC P1870. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. Ensure final drive ratio matches PCM calibration. The following mechanical conditions could set DTC P1870: shift solenoids, TCC PWM solenoid, internal transmission failures or engine misfire.

The 4WD low circuit consists of a transfer case switch, an indicator light and wiring. When 4WD low is engaged, voltage to PCM changes from ignition voltage to zero voltage. The 4WD low switch signal corrects transmission output shaft speed signal to PCM. This signal compensates for transfer case gear reduction. PCM utilizes transmission output shaft speed signal to adjust shift points, line pressure and TCC apply and release.

Conditions For Setting DTC P1875

DTC will set under the following conditions

1. 4WD low is stuck on for 5 seconds with transfer case ratio of .95-1.05:1, in any one gear.
2. 4WD low is stuck off for 1.5 seconds with transfer case ratio of 2.66-2.76:1, in any 2 gears.

PCM performs the following if DTC is set

1. Freezes shift adapts from being updated.
2. Defaults to a low state shift pattern when 4WD low is stuck off and a high state shift pattern when stuck on.
3. Illuminates MIL.
4. Stores DTC P1875 in PCM history.

Note. Active type transfer case uses active transfer case control module; non-active type transfer case uses transfer case switch.

1. Turn ignition off. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records data for reference, and then clear DTCs. Place transmission in Neutral. While monitoring scan tool display, select 4WD High, and then 4WD Low on transfer case selector lever. If scan tool displays DISABLED with 4WD High selected, and ENABLED with 4WD Low selected, go to next step. If scan tool display is not as specified, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/automatic-trans/#automatic-transmission-diagnosis-4l80-e-diesel-4-digit-codes) .
2. Turn ignition off. Disconnect transfer case control module (active transfer case) or switch connector (non-active transfer case). Turn ignition on. If 4WD Low on scan tool indicates ENABLED, go to step 5 . If 4WD Low on scan tool does not indicate ENABLED, go to next step.
3. Using jumper wire, ground 4WD Low signal circuit (Gray/Black wire). If 4WD Low on scan tool indicates ENABLED, go to next step. If 4WD Low on scan tool does not indicate ENABLED, go to step 6 .
4. Replace active transfer case control module or transfer case switch. After repairs, go to step 8 .
5. Check 4WD Low signal circuit for short to ground. If circuit is shorted, repair as necessary. After repairs, go to step 8 . If circuit is okay, go to next step.
6. Check 4WD Low signal circuit for an open. If circuit is open, repair as necessary. After repairs, go to step 8 . If circuit is okay, go to next step.
7. Replace PCM. After repairs, go to next step.
8. Using scan tool, clear DTCs. Test drive vehicle in 4WD High and 4WD Low. Using scan tool, check for DTCs. If no DTCs are set, system is okay. If DTC P1875 is set, go to step 1 .

Inspect wiring for poor connections at PCM. Check for bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wires that could short to bare metal or other wiring. Check for broken wires inside their insulation. If diagnosing for intermittent short or open conditions, move wiring harness while observing scan tool for value changes. First diagnose and clear any engine-related and TP sensor DTCs that are present, and then inspect for any transmission-related DTCs that may have reset. Low oil pump pressure and a slipping transmission can cause DTC P1875 to set.

Note. After repair is complete, a harsh shift condition may exist. This condition is caused by steady state adapts. To clear steady state adapt cells, select "clear taps" with scan tool, or remove battery power from PCM for 60 seconds. Then reconnect battery and drive vehicle.

Automatic Transmission Wiring Diagram ("C" & "K" Series - 6.5L RPO L65). Scheme 153

Automatic Transmission Wiring Diagram ("G" Series - 6.5L RPO L65). Scheme 154

Automatic Transmission Wiring Diagram ("P" Series - 6.5L RPO L57 & L65). Scheme 155

See also:
• MODEL IDENTIFICATION
• ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
• CONNECTOR IDENTIFICATION
• MIL INOPERATIVE
• NO DATA LINK CONNECTOR (DLC) DATA
• P0741
• P0742
• DIAGNOSTIC TESTS
• CLEARING DIAGNOSTIC TROUBLE CODES
• DIAGNOSTIC AIDS
• TFP MANUAL VALVE POSITION SWITCH & WIRE HARNESS RESISTANCE CHECKS