DTC P1756: GOVERNOR PRESSURE NOT EQUAL TO TARGET @ 35-40 PSI (DIESEL)

Circuit Description

Circuit is monitored continuously while ignition is on and engine is running, not in Park or Neutral. DTC sets if governor pressure sensor output is less than 15 psi (1.0 kg/cm2 ) or more than 30 psi (2.1 kg/cm2 ) when requested pressure is 20-25 psi (1.4-1.7 kg/cm2 ) for 2.2 seconds. Test must fail 5 times to set DTC.

Possible Cause

• The following items may be area of concern:
• Other transmission-related DTCs are set.
• Solenoid pack connector 5-volt supply circuit open.
• Sensor signal circuit has short to ground, short to voltage or open.
• Governor pressure sensor defective.
• Transmission fluid burnt or oil pan contains excessive debris.
• Governor pressure out of range.
• Transmission leaking internally.
• Defective PCM.
• Defective valve body.

Diagnostic Procedure

1. Using scan tool, read DTCs. If good trip counter for DTC P1756 is not displayed or displayed count is not zero, go to next step. If good trip counter is displayed and displayed count is zero, go to step 31 .

2. Repair any other transmission-related DTCs before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS under SELF-DIAGNOSTIC SYSTEM. If no other transmission-related DTCs exist, go to next step.

3. Start engine. Allow engine to reach normal operating temperature. Check transmission fluid for proper level and for any debris. Fill or repair transmission as necessary. See appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If fluid level and condition are okay, go to next step.

4. Set parking brake, depress brake pedal and place gearshift lever in "D" position. Using scan tool, observe governor pressure sensor pressure. If pressure is greater than 3 psi (.2 kg/cm2 ), go to next step. If pressure is 3 psi (.2 kg/cm2 ) or less, go to step 26 .

5. Turn ignition off. Install a pressure gauge at transmission governor pressure test port. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS. Start engine. With gearshift lever in "D" position, observe gauge pressure. If pressure is 5 psi (.3 kg/cm2 ) or more, go to step 29 . If pressure is less than 5 psi (.3 kg/cm2 ), go to next step.

6. Turn ignition off. Disconnect transmission solenoid assembly harness connector. Turn ignition on. Measure voltage between ground and 5-volt supply circuit at transmission solenoid harness connector terminal No. 2. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to step 19 .

7. Turn ignition off. Disconnect PCM harness connector C2 (White). Measure resistance of governor pressure sensor signal circuit between transmission solenoid harness connector terminal No. 4 and PCM harness connector C2 (White) terminal No. 29. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair governor pressure sensor signal circuit for open.

8. Disconnect PCM harness connector C1 (Black). Measure resistance of sensor ground circuit between transmission solenoid harness connector terminal No. 3 and PCM harness connector C1 (Black) terminal ground circuit for open.

9. Measure resistance of governor pressure sensor signal circuit between ground and transmission solenoid harness connector terminal No. 4. If resistance is less than 5 ohms, repair signal circuit for short to ground. If resistance is 5 ohms or more, go to next step.

10. Measure resistance between sensor signal circuit and sensor ground circuit at transmission solenoid harness connector terminals No. 3 and 4. If resistance is less than 5 ohms, repair governor pressure sensor circuit for short to sensor ground circuit. If resistance is 5 ohms or more, go to next step.

11. Turn ignition on. Measure voltage of governor pressure sensor signal circuit between ground and transmission solenoid assembly connector terminal No. 4. If voltage is one volt or less, go to next step. If voltage is more than one volt, repair sensor signal circuit for short to voltage.

12. Turn ignition off. Ensure transmission solenoid harness connector is disconnected. Remove transmission oil pan. See appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Disconnect governor pressure/temperature sensor harness connector. Inspect connector and terminals for damage. Repair as necessary. Measure resistance of governor pressure sensor 5-volt supply circuit between governor pressure/temperature sensor harness connector terminal "A" and transmission solenoid harness connector terminal No. 2. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

13. Measure resistance of sensor ground circuit between governor pressure/temperature sensor harness connector terminal "D" and transmission solenoid harness connector terminal No. 3. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

14. Measure resistance of governor pressure sensor signal circuit between governor pressure/temperature sensor harness connector terminal "B" and transmission solenoid harness connector terminal No. 4. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

15. Measure resistance of governor pressure sensor signal circuit between ground and governor pressure/temperature sensor harness connector terminal "B". If resistance is less than 5 ohms, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If resistance is 5 ohms or more, go to next step.

16. Measure resistance between governor pressure sensor signal circuit and sensor ground circuit at governor pressure/temperature sensor harness connector terminals "B" and "D". If resistance is less than 5 ohms, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If resistance is 5 ohms or more, go to next step.

17. Reconnect transmission solenoid assembly harness connector. Turn ignition on. Measure voltage of governor pressure sensor signal circuit between ground and governor pressure/temperature sensor harness connector terminal "B". If voltage is more than one volt, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If voltage is one volt or less, go to next step.

18. Turn ignition off. Using DVOM, backprobe governor pressure sensor signal circuit at PCM harness connector C2 (White) terminal No. 29. Start and idle engine. Place gearshift lever in "N" position. Using scan tool, observe governor pressure sensor voltage. Compare scan tool value with DVOM voltage. If voltages match, replace governor pressure/temperature sensor. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If voltages do not match, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.

19. Turn ignition off. Disconnect PCM harness connector C2 (White). Measure resistance of governor pressure sensor signal circuit between transmission solenoid harness connector terminal No. 4 and PCM harness connector C2 (White) terminal No. 29. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair governor pressure sensor signal circuit for open.

20. Ensure transmission solenoid harness connector is disconnected. Measure resistance of 5-volt supply circuit between transmission solenoid harness connector terminal No. 2 and PCM harness connector C2 (White) terminal No. 31. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair 5-volt supply circuit for open.

21. Disconnect PCM harness connector C1 (Black). Measure resistance of sensor ground circuit between transmission solenoid harness connector terminal No. 3 and PCM harness connector C1 (Black) terminal No. 4. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair sensor ground circuit for open.

22. Measure resistance of governor pressure sensor signal circuit between ground and transmission solenoid harness connector terminal No. 4. If resistance is less than 5 ohms, repair signal circuit for short to ground. If resistance is 5 ohms or more, go to next step.

23. Measure resistance between governor pressure sensor signal circuit and sensor ground circuit at transmission solenoid assembly harness connector terminals No. 3 and 4. If resistance is less than 5 ohms, repair governor pressure sensor circuit for short to sensor ground circuit. If resistance is 5 ohms or more, go to next step.

24. Turn ignition on. Measure voltage of governor pressure sensor signal circuit between ground and transmission solenoid assembly harness connector terminal No. 4. If voltage is more than one volt, repair signal circuit for short to voltage. If voltage is one volt or less, go to next step.

25. Turn ignition off. Ensure transmission solenoid harness connector is disconnected. Remove transmission oil pan. See appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Disconnect governor pressure/temperature sensor harness connector. Inspect connector and terminals for damage. Repair as necessary. Measure resistance of governor pressure sensor ground circuit between governor pressure/temperature sensor harness connector terminal "D" and transmission solenoid harness connector terminal No. 3. If resistance is less than 5 ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. If resistance is 5 ohms or more, replace transmission solenoid assembly (internal transmission harness). See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

26. Start and idle engine. Ensure engine and transmission are at normal operating temperature. Place gearshift lever in "P" position. With engine running, remove trP1756 Gov Press Not Equal To Target @ 35-40 PSI (Diesel)ansmission control relay from underhood Power Distribution Center (PDC) or Integrated Power Module (IPM), as applicable. Depress brake pedal and place gearshift lever in "D" position. Using scan tool, observe governor pressure. If pressure is 40-55 psi (2.8-3.9 kg/cm2 ), go to next step. If pressure is not 40-55 psi (2.8-3.9 kg/cm2 ), go to step 28 .

27. Turn ignition off. Replace governor pressure solenoid. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Test drive vehicle at 25-30 MPH. Using scan tool, monitor governor actual pressure and target pressure. If pressures do not remain constant within 5 psi (.3 kg/cm2 ) of each other, repair internal transmission leakage problem. If pressures remain constant within 5 psi (.3 kg/cm2 ) of each other, testing is complete.

28. Turn ignition off. Connect a 0-300 psi (0-21 kg/cm2 ) pressure gauge to transmission governor pressure test port. See HYDRAULIC PRESSURE TESTS under PERFORMANCE TESTS. Ensure engine and transmission are at normal operating temperature. Place gearshift lever in "P" position. Start and idle engine. With engine running, remove transmission control relay from underhood Power Distribution Center (PDC) or Integrated Power Module (IPM), as applicable. Depress brake pedal and place gearshift lever in "D" position. Observe governor pressure on gauge. If pressure is 40-55 psi (2.8-3.9 kg/cm2 ), testing is complete. If pressure is not 40-55 psi (2.8-3.9 kg/cm2 ), go to next step.

29. Turn engine off. Install transmission control relay. Drain transmission fluid and remove oil pan. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC
TRANSMISSIONS. Inspect pan for burnt oil and debris. Repair transmission as necessary. See appropriate OVERHAUL article. If transmission is okay, go to next step.

30. Replace governor pressure solenoid. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Start engine and warm to normal operating temperature. Depress brake pedal and place gearshift lever in "D" position. Observe gauge pressure. If pressure is less than 5 psi (.3 kg/cm2 ), testing is complete. If pressure is 5 psi (.3 kg/cm2 ) or more, replace valve body. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC
TRANSMISSIONS.

31. Conditions required to set DTC are currently not present. Inspect all applicable connectors and terminals for damage. Repair as necessary. If connectors and terminals are okay, see INACTIVE DTC CONDITION under SELF-DIAGNOSTIC SYSTEM. Testing is complete.