Transmission Control Module (TCM) - NAG1

P0712-TRANSMISSION TEMPERATURE SENSOR LOW





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Electrohydraulic Control Unit Assembly of the NAG1 transmission contains a temperature sensor to monitor the transmission oil temperature. This sensor is wired in series with the transmission Park/Neutral switch. The Transmission Control Module (TCM) expects to see a valid voltage level from the sensor when the shifter is in Reverse or any forward Drive position. The TCM also expects to see an open circuit condition when the shifter is in the Park or Neutral position. When the controller detects an open circuit when in Reverse or any forward drive position the DTC will set. Note: The TCM substitutes the Transmission Temperature reading with Engine Temperature due to a open circuit condition in Park or Neutral.

- When Monitored:
Continuously with the ignition on.

- Set Condition:
When the TCM detects the Temperature sensor input is below 0.5 volts.





Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. NAG1 Pre-Diagnostic Troubleshooting Procedure

1. CHECK FOR SHIFT LEVER ASSEMBLY DTCS
1. With the scan tool, check for Shift Lever Assembly DTCs.

Are there any Shift Lever Assembly DTCs present?

Yes

- Testing and Inspection
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Go To 2

2. CHECK THE SHIFT LEVER ASSEMBLY CABLE FOR PROPER ADJUSTMENT
1. Check the Shift Lever Assembly Cable for proper adjustment. Refer to AUTOMATIC TRANSMISSION-AUTOMATIC TRANSMISSION NAG1/SERVICE INFORMATION for the appropriate service procedure.

Is the Shift Lever Assembly Cable for properly adjusted?

Yes

- Go To 3

No

- Adjust the Shift Lever Assembly Cable.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

3. CHECK THE (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Turn the ignition off to the lock position.
2. Disconnect the TCM C2 harness connector.
3. Measure the resistance between ground and the (T54) Temperature Sensor-P/N Switch Signal circuit.

Is the resistance below 5.0 ohms?

Yes

- Repair the (T54) Temperature Sensor-P/N Switch Signal circuit for a short to ground.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Go To 4

4. CHECK THE (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




1. Disconnect the TCM C1 harness connector.
2. Disconnect the Transmission Electrohydraulic Control Unit Assembly harness connector.
3. Measure the resistance between the (T54) Temperature Sensor-P/N Switch Signal circuit and all other circuits in the TCM C1 and C2 harness connectors.

Is the resistance below 5.0 ohms between the (T54) Temperature Sensor-P/N Switch Signal circuit and any other circuit(s)?

Yes

- Repair the (T54) Temperature Sensor-P/N Switch Signal circuit for a short to another circuit(s).
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals 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 TCM.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test