Automatic Transaxle Diagnosis - 4T65-E: Other Chevrolet Venture I

POWERTRAIN CONTROL MODULE

PCM controls ignition, fuel and emission devices related to engine and transaxle operation. PCM receives electronic signals from sensors and switches. Input signals enable PCM to determine when to operate various relays and solenoids related to engine and transaxle control. PCM utilizes 2 different colored 80-pin connectors. (Scheme 85)and (Scheme 86).

POWERTRAIN CONTROL MODULE LOCATIONS

LIMP-IN MODE

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

Internal Mode Switch (Bonneville, Impala, Monte Carlo & Park Avenue)

The Internal Mode Switch (IMS) is a sliding contact switch attached to the selector detent inside transaxle side cover. see scheme 1 The IMS replaces the Park/Neutral Position (PNP) switch, which is used on all other models. IMS communicates switch position information to PCM, and is used for engine controls and for determining transaxle shift patterns.

Shift Solenoids 1-2 & 2-3

Transaxle shifting is performed by 2 electric shift solenoids. Both solenoids are located on control valve body. Ignition power is supplied to each solenoid by fused circuit. See WIRING DIAGRAMS .

1-2 shift solenoid controls hydraulic pressure to 1-2 shift valve. 2-3 shift solenoid controls hydraulic pressure to 3-4 shift valve.

Pressure Control Solenoid

Pressure control solenoid is an electronic pressure regulator which controls transaxle line pressure. see scheme 1 PCM sends a frequency signal (duty cycle) to pressure control solenoid to regulate hydraulic line pressure. When duty cycle is zero, line pressure is at maximum, and pressure control solenoid draws zero amps. When duty cycle is 90 percent, line pressure is at minimum, and pressure control solenoid draws 1.1 amps.

Hard Failures

Most hard failures cause MIL to illuminate and remain illuminated until malfunction is repaired. If MIL illuminates and remains illuminated (light may flash) during vehicle operation, cause of malfunction must be determined.

If a sensor fails, PCM will use a substitute value in its calculations to continue engine and/or transaxle operation. In this condition, vehicle is functional, and will most likely display degraded driveability. See LIMP-IN MODE .

Intermittent Failures

Intermittent failures cause MIL to flicker or glow and turn off about 10 seconds after intermittent fault goes away. Corresponding DTC, however, will be retained in PCM memory. If related fault does not reoccur within 50 engine starts, DTC will be erased from PCM memory. Intermittent failures may be caused by sensor, connector or wiring related problems.

HARD OR INTERMITTENT CODE DETERMINATION

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

1. Enter diagnostic mode. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-11647-S23683777482001051400000) . Read and record all stored DTCs. Exit diagnostic mode and clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-11647-S42407736892000112200000) .
2. Apply parking brake and place transaxle 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, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. DTCs may require a road test to reset hard failure after clearing DTCs. If MIL does not illuminate, all stored DTCs were intermittent failures.

NO DATA LINK CONNECTOR DATA

If scan tool does not display PCM data, see DLC DIAGNOSIS OR NO SCAN TOOL DATA under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

NO MALFUNCTION INDICATOR LIGHT

If MIL does not illuminate, see MIL INOPERATIVE or MIL CIRCUIT CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

Scheme 82

Scheme 83

Scheme 84

Scheme 85

Scheme 86

Action Taken By PCM

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Freezes shift adapts.
3. DTC P0218 is recorded in history.

PCM performs the following actions if DTC is set

1. Illuminates MIL after 2 consecutive ignition cycles in which conditions for setting DTC are met.
2. Freezes shift adapts from being updated.
3. DTC P0503 is recorded in history.
4. Commands maximum line pressure.
5. Calculates vehicle speed using input speed sensor information for shift timing.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Freezes shift adapts from being updated.
3. DTC P0711 is recorded in history.
4. Calculates default transaxle fluid temperature from ECT and IAT sensors.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Freezes shift adapts from being updated.
3. DTC P0712 is recorded in history.
4. Calculates default transaxle fluid temperature from ECT and IAT sensors.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Freezes shift adapts from being updated.
3. DTC P07123 is recorded in history.
4. Calculates default transaxle fluid temperature from ECT and IAT sensors.

PCM performs the following actions if DTC is set

1. Illuminates MIL after 2 consecutive ignition cycles in which conditions for setting DTC are met.
2. Inhibits TCC operation.
3. Freezes shift adapts from being updated.
4. Inhibits 4th gear if transaxle is in hot mode.
5. DTC P0716 is recorded in history.

PCM performs the following actions if DTC is set

1. Illuminates MIL after 2 consecutive ignition cycles in which conditions for setting DTC are met.
2. Inhibits TCC operation.
3. Freezes shift adapts from being updated.
4. Inhibits 4th gear if transaxle is in hot mode.
5. DTC P0717 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Disregards brake switch for TCC scheduling.
3. DTC P0719 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. DTC P0724 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. DTC P0730 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates during second consecutive trip in which conditions for setting DTC are met.
2. Inhibits TCC.
3. Inhibits 4th gear if transaxle is in hot mode.
4. Freezes shift adapts.
5. Records operating conditions when conditions for setting DTC are met.
6. DTC P0741 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands TCC on at maximum capacity.
3. Freezes shift adapts.
4. Records operating conditions when conditions for setting DTC are met.
5. DTC P0741 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL is not illuminated.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. DTC P0748 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. DTC P0751 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. Inhibits 3-2 downshifts when vehicle speed is more than 30 MPH.
5. DTC P0752 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Inhibits TCC.
4. Freezes shift adapts.
5. Inhibits 3-2 downshifts when vehicle speed is more than 30 MPH.
6. DTC P0753 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Inhibits TCC.
4. Freezes shift adapts.
5. Commands 3rd gear.
6. DTC P0756 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Inhibits TCC.
4. Freezes shift adapts.
5. Commands 3rd gear.
6. DTC P0758 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL illuminates.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. DTC P1810 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. Commands maximum line pressure.
3. Freezes shift adapts.
4. DTC P1811 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1814 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1819 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1820 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1822 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1823 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1825 is recorded in history.

PCM performs the following actions if DTC is set

1. MIL does not illuminate.
2. DTC P1826 is recorded in history.

PCM performs the following actions if DTC is set

1. Illuminates MIL during 2nd consecutive trip in which conditions for setting DTC are met.
2. Inhibits TCC.
3. Inhibits 4th gear if transaxle is in hot mode.
4. Freezes shift adapts.
5. DTC P1860 is recorded in history.

PCM performs the following actions if DTC is set

1. Illuminates MIL during 2nd consecutive trip in which conditions for setting DTC are met.
2. Inhibits TCC.
3. Inhibits 4th gear if transaxle is in hot mode.
4. Freezes shift adapts.
5. DTC P1887 is recorded in history.

COMPONENT RESISTANCE

Connect DVOM between specified terminals at component or at transaxle 20-pin in-line connector to transaxle. Measure individual component resistance at specified temperature. (Scheme 83) See COMPONENT RESISTANCE SPECIFICATIONS table. If resistance is not as specified, replace appropriate component. (Scheme 87)

COMPONENT RESISTANCE SPECIFICATIONS

Scheme 87

TRANSAXLE RANGE SWITCH

Note. Transaxle range switch is also referred to as Park/Neutral Position (PNP) switch.

1. Connect scan tool. Turn ignition on, engine off. Using scan tool, observe range switch display while selecting each transaxle range. If each range selection matches scan tool display, see «DIAGNOSTIC AIDS»(ref-11647-S16820875422001051400000). If range selection does not match scan tool display, go to next step.
2. Using scan tool, observe range switch A/B/C/P display. If HI is indicated for all range signal states, go to step 11. If HI is not indicated for all range states, go to next step.
3. Turn ignition off. Remove transaxle side cover. See HYDRA-MATIC 4T65-E OVERHAUL article. Disconnect transaxle range switch connector. Turn ignition on, engine off. Using scan tool, observe range switch A/B/C/P display. If HI is indicated for all range signal states, go to next step. If HI is not indicated for all range states, go to step 8.
4. Using DVOM, measure voltage between ground and terminals "B", "C" and "D" of range switch harness connector, one at a time. (Scheme 84) If voltage is 10-12 volts, go to next step. If voltage is not 10-12 volts, go to step 9.
5. Connect a fused jumper wire between ground and terminal "D" of range switch connector (signal circuit "A") while monitoring scan tool range switch A/B/C/P parameter. If any other signal circuits display LOW when terminal "A" is grounded, go to step 10. If only signal "A" indicates LOW, go to next step.
6. Connect fused jumper wire between ground and terminal "B" of range switch connector (signal circuit "B") while monitoring scan tool range switch A/B/C/P parameter. If any other signal circuits display LOW when terminal "B" is grounded, go to step 10. If only signal "B" indicates LOW, go to next step.
7. Connect fused jumper wire between ground and terminal "C" of range switch connector (signal circuit "C") while monitoring scan tool range switch A/B/C/P parameter. If any other signal circuits display LOW when terminal "C" is grounded, go to step 10. If only signal "C" indicates LOW, go to step 12.
8. Check for short to ground in range switch signal circuits not indicating HI. Repair as necessary. After repairs, go to step 14. If range switch signal circuits are okay, go to step 13.
9. Check for open in range switch signal circuits not indicating correct voltage. Repair as necessary. After repairs, go to step 14. If range signal circuits are okay, go to step 13.
10. Check for shorted together condition in affected range switch signal circuits. Repair as necessary. After repairs, go to step 14. If range switch signal circuits are okay, go to step 13.
11. Check for open in range switch ground circuit. Repair as necessary. After repairs, go to step 14. If range switch ground circuit is okay, go to next step.
12. Replace transaxle range switch. See HYDRA-MATIC 4T65-E OVERHAUL article. After repairs, go to step 14.
13. Replace PCM. After replacement, program PCM. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. After repairs, go to next step.
14. Connect scan tool. Turn ignition on, engine off. Using scan tool, observe range switch display while selecting each transaxle range. If each range selection matches scan tool display, system is okay. If selections do not match scan tool display, repeat test.