48RE Automatic Transmission - Diesel

P0712-TRANS TEMP SENSOR VOLTAGE TOO LOW (DIESEL)





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


Theory of Operation


The Transmission Temperature Sensor is used to sense when the transmission temperature is too hot or too cold to operate overdrive and/or the torque convertor clutch. When the transmission sensor detects a temperature below 0� C (32� F), overdrive and the torque convertor clutch are disabled. When the detected temperature is above 127� C (260� F), overdrive is disabled and 3rd gear with TCC is engaged, this strategy is used to increase transmission fluid flow to help cool the transmission.


- When Monitored:

Continuously with the ignition on and the engine running.

- Set Condition:

The DTC will set if the monitored Transmission Temperature Sensor Signal circuit drops below 1.55 volts for the period of 2.25 seconds.







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



Diagnostic Test


1. CHECK IF THE DTC IS CURRENT

Ignition on, engine not running.

With the scan tool, read Engine DTCs.

Record the Freeze Frame data for the reported DTC.

With the scan tool, erase DTCs.

Turn the ignition off to the lock position.

Using the Freeze Frame data recorded earlier, try to duplicate the conditions in which the DTC originally set.


NOTE: It may be necessary to road test the vehicle to duplicate the original set conditions.

With the scan tool, read Engine DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Go To 8



2. CHECK THE (T54) TRANSMISSION TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND





Turn the ignition off to the lock position.

Disconnect the ECM C2 harness connector.

Disconnect the Transmission Solenoid Assembly harness connector.

Measure the resistance between ground and the (T54) Transmission Temperature Sensor Signal circuit in the Transmission Solenoid Assembly harness connector.

Is the resistance above 100k ohms?

Yes

- Go To 3

No

- Repair the (T54) Transmission Temperature Sensor Signal circuit for a short to ground.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test


3. CHECK THE (T54) TRANSMISSION TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO (K900) SENSOR GROUND CIRCUIT





Measure the resistance between the (T54) Transmission Temperature Sensor Signal circuit and (K900) Sensor Ground circuit in the Transmission Solenoid Assembly harness connector.

Is the resistance above 100k ohms?

Yes

- Go To 4

No

- Repair the (T54) Transmission Temperature Sensor Signal circuit for a short to the (K900) Sensor Ground circuit.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test

4. CHECK THE (T54) TRANSMISSION TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND INSIDE TRANSMISSION





Remove the Transmission Oil Pan.

Disconnect the Governor Pressure Sensor connector internal to the transmission.

Measure the resistance between ground and the (T54) Transmission Temperature Sensor Signal circuit at the Governor Pressure Sensor connector.

Is the resistance above 100k ohms?

Yes

- Go To 5

No

- Replace the Transmission Solenoid Assembly.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test


5. CHECK THE (T54) TRANSMISSION TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO (K900) SENSOR GROUND CIRCUIT INSIDE TRANSMISSION





Measure the resistance between the (T54) Transmission Temperature Sensor Signal circuit and (K900) Sensor Ground circuit at the Governor Pressure Sensor connector.

Is the resistance above 100k ohms?

Yes

- Go To 6

No

- Replace the Transmission Solenoid Assembly.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test


6. TRANSMISSION TEMPERATURE SENSOR










Measure the resistance of the Transmission Temperature Sensor between the (T54) Transmission Temperature Sensor Signal circuit and (K900) Sensor Ground circuit.

Using the chart above, compare the Temperature Sensor temperature to the correlating resistance value.

Is the resistance below the minimum specification for the sensor temperature?

Yes

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

No

- Go To 7



7. ENGINE CONTROL MODULE

Reconnect the all disconnected connectors.

Ignition on, engine not running.

With the scan tool, erase Engine DTCs.

With the scan tool, monitor Engine DTC's.

Disconnect the Transmission Temperature Sensor connector.

Did the DTC P0713 set?

Yes

- Go To 8

No

- Replace and program the Engine Control Module.
- Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). Transmission Verification Test



8. INTERMITTENT WIRING AND CONNECTORS

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

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

Using the schematics as a guide, 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.

Wiggle the wiring and connectors while checking for any possible open or shorted circuits.

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.