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 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)

Go To 2

2.CHECK THE SHIFT LEVER ASSEMBLY CABLE FOR PROPER ADJUSTMENT

(Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1/GEAR SHIFT CABLE - ADJUSTMENTS)

Is the Shift Lever Assembly Cable properly adjusted?

Yes

Go To 3

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

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)

Go To 4

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

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)

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)