P0712-TRANSMISSION TEMPERATURE SENSOR LOW
For a complete wiring diagram Refer to Section 8W
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.
| Possible Causes |
| (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT SHORT TO GROUND |
| (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT SHORT TO ANOTHER CIRCUIT |
| TRANSMISSION TEMPERATURE SENSOR-P/N SWITCH |
| TRANSMISSION CONTROL MODULE |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
Diagnostic Test
1. CHECK FOR SHIFT LEVER ASSEMBLY DTCSWith the scan tool, check for Electronic Shift Module (ESM) DTCs.
Are there any Shift Lever ESM DTCs present?
Yes
- Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - DIAGNOSIS & TESTING and perform the appropriate symptom.
- Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 2
2. CHECK THE SHIFT LEVER ASSEMBLY CABLE FOR PROPER ADJUSTMENT
Check the Shift Lever Assembly Cable for proper adjustment per the Service Information. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1/GEAR SHIFT CABLE - ADJUSTMENTS)
Is the Shift Lever Assembly Cable properly adjusted?
Yes
- Go To 3
No
- Adjust the Shift Lever Assembly Cable per the Service Information.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
3. CHECK THE (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND
Turn the ignition off to the lock position.
Disconnect the TCM C2 harness connector.
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. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Go To 4
4. CHECK THE (T54) TEMPERATURE SENSOR-P/N SWITCH SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT
Disconnect the TCM C1 harness connector.
Disconnect the Transmission Electrohydraulic Control Unit Assembly harness connector.
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. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)
No
- Using the schematics as a guide, check the Transmission Control Module (TCM) 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 the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE - REMOVAL)
- Perform NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)