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P1756






P1756-GOV PRESS NOT EQUAL TO TARGET @ 35 - 40 PSI (DIESEL)





For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams


Theory of Operation


The Governor Pressure Control System is used to regulate the governor pressure which controls the shifts for first, second, and third gear. The Governor Pressure Control System test verifies that the requested pressure and the actual pressure are within a predetermined tolerance.


- When Monitored:

While driving and the commanded governor pressure is equal to the pressure required for third gear.

- Set Condition:

If the governor pressure sensor output is less than 407 kPa (60 psi) or greater than 621 kPa (80 psi) when the requested pressure is 407 - 621 kPa (60 - 80 psi) for 2.2 seconds. This DTC will set if there are two trips of five consecutive bad 2.2 second tests with the transmission oil temperature between 23.5 - 88� C (74 - 190� F).







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Checkout (Diesel)



Diagnostic Test


1. CHECK IF OTHER TRANSMISSION DTCS ARE PRESENT

Ignition on, engine not running.

With the scan tool, read Engine DTCs.

Are any other transmission DTCs present?

Yes

- Refer to the Transmission category and perform the appropriate symptom(s).

No

- Go To 2



2. CHECK IF THE GOVERNOR PRESSURE IS ABOVE 3 PSI IN DRIVE


CAUTION: Apply the parking brake.

Start the engine and allow the transmission to reach normal operating temperature above 43� C (110� F).


CAUTION: Apply the brakes.

With the engine at idle, place the gear selector in Drive.

With the scan tool, read the Governor Pressure.

Is the Governor Pressure above 21 kPa (3 psi)?

Yes

- Go To 3

No

- Go To 4



3. CHECK IF THE GOVERNOR PRESSURE IS BELOW 3 PSI

Turn the ignition off to the lock position.

Install a pressure gauge at the Governor Pressure test port.


NOTE: Use the appropriate pressure gauge for the pressure range measured.


CAUTION: Apply the parking brake.

Start the engine and allow the transmission to reach normal operating temperature above 43� C (110� F).


CAUTION: Apply the brakes.

With the engine at idle, place the gear selector in Drive.

Read the governor pressure on the pressure gauge.

Is the governor pressure on the pressure gauge below 21 kPa (3 psi) with the engine at idle and the gear selector in Drive?

Yes

- The Governor Pressure Solenoid is functioning properly. Go To 7

No

- Go To 10



4. GOVERNOR PRESSURE BETWEEN 40-55 WITH RELAY REMOVED

Place the gear selector in Park.

Turn the ignition off to the lock position.

Disconnect the TIPM C1 connector.

Start the engine and allow the transmission to reach normal operating temperature above 43� C (110� F).


WARNING: Do not wear loose clothing or jewelry when working on or near a running engine. Failure to follow these instructions can result in personal injury or death.


NOTE: Disconnecting the TIPM connector may set various DTCs. Disregard any DTC that may set due to disconnecting the connector.


CAUTION: Apply the brakes.

Place the gear selector in Drive and allow the engine to idle for 30 seconds.

With the scan tool, read the Actual Governor Pressure at idle.

Is the governor pressure on the scan tool between 276 - 379 kPa (40 - 55 psi)?

Yes

- Go To 5

No

- Go To 6



5. GOVERNOR PRESSURE SOLENOID

Turn the ignition off to the lock position.

Replace the Governor Pressure Solenoid.

Start the engine and allow the transmission to reach normal operating temperature above 43� C (110� F).

With the scan tool, monitor the target governor pressure and actual governor pressure.

Drive the vehicle at a constant speed 40 - 48 Km/h (25 - 30 MPH).


NOTE: The Actual Governor Pressure should be within 21 kPa (3 psi) of the Target Governor Pressure within 3 seconds.

Is the Actual Governor Pressure within 21 kPa (3 psi) of the Target Governor Pressure?

Yes

- Go To 13

No

- Repair internal transmission leak. Inspect all components pertaining to the Governor Pressure Sensor and the Governor Pressure Solenoid.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



6. CHECK GAUGE PRESSURE 40-55 WITH RELAY OUT

Place the gear selector in Park.

Turn the ignition off to the lock position.

Disconnect the TIPM C1 connector.

Start the engine and allow the transmission to reach normal operating temperature above 43� C (110� F).


WARNING: Do not wear loose clothing or jewelry when working on or near a running engine. Failure to follow these instructions can result in personal injury or death.


NOTE: Disconnecting the TIPM connector may set various DTCs. Disregard any DTC that may set due to disconnecting the connector.


CAUTION: Apply the brakes.

Place the gear selector in Drive with the engine at idle.

Read the governor pressure on the pressure gauge.

Is the governor pressure on the pressure gauge read between 276 - 379 kPa (40 - 55 psi)?

Yes

- Go To 7

No

- Go To 10



7. CHECK THE 5 VOLT SUPPLY CIRCUIT FOR AN OPEN - EXTERNAL





Turn the ignition off to the lock position.

Disconnect the Transmission Solenoid Assembly harness connector.

Disconnect the ECM harness connectors.

Measure the resistance of the 5-volt Supply circuit between the Transmission Solenoid Assembly harness connector and the ECM C2 harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 8

No

- Repair the 5-volt Supply circuit for an open.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



8. CHECK THE 5 VOLT SUPPLY CIRCUIT FOR AN OPEN - INTERNAL





Remove the transmission oil pan.

Reconnect the Transmission Solenoid Assembly harness connector.

Disconnect the Governor Pressure Sensor connector internal to the transmission.

Measure the resistance of the 5-volt Supply circuit between the ECM C2 harness connector and the Governor Pressure sensor connector internal to the transmission.

Is the resistance below 5.0 ohms?

Yes

- Go To 9

No

- Repair or replace the 5-volt Supply circuit for an open internal to the transmission.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



9. GOVERNOR PRESSURE SENSOR





Reconnect the ECM harness connectors.


NOTE: The ECM harness connectors must not be disconnected during this test.

Ignition on, engine not running.

Measure the voltage of the 5-volt Supply circuit at the Governor Pressure Sensor connector internal to the transmission.

Is the voltage between 4.5 and 5.5 volts?

Yes

- Replace the Governor Pressure/Transmission Temperature Sensor.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Using the schematics as a guide, check the Engine Control Module (ECM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the ECM.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



10. TRANSMISSION - INTERNAL DAMAGE

Turn the ignition off to the lock position.

Remove the transmission oil pan.

Inspect the transmission oil pan for burnt transmission fluid and/or excessive debris.

Is the transmission fluid burnt and/or contain excessive debris?

Yes

- Repair the internal transmission.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Go To 11



11. CHECK THE VALVE BODY

Replace the Governor Pressure Solenoid.

Install a pressure gauge at the governor pressure test port.

Start the engine.

Warm the transmission to normal operating temperature.


CAUTION: Apply the brakes.

Place the gear selector in Drive and allow the engine to idle.

Read the governor pressure on the pressure gauge in Drive.

Is the governor pressure on the gauge below 21 kPa (3 psi)?

Yes

- Go To 12

No

- Repair or replace the Valve Body.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

12. VERIFY OPERATION - TEST DRIVE

Remove the pressure gauge from the transmission.

Test drive the vehicle.

Be sure to drive the vehicle at a constant speed of 40-48 Km/h or 25-30 MPH during the drive cycle.

With the scan tool, read Engine DTCs.

Did the DTC reset?

Yes

- Using the schematics as a guide, check the Engine Control Module (ECM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the ECM.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Test Complete.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



13. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary set this DTC are not present at this time.

Use the Freeze Frame Data to help duplicate the conditions that set the DTC. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load.

Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.

Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

No

- Test Complete.
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