95 1/2 Model

This Diagnostic Trouble Code (DTC) does not flash the "CHECK TRANS" Indicator and does not set the Backup Mode.




Circuit Description
- The Engine Coolant Temperature (ECT) is measured by a Sensor in the Coolant System. This information is used by the Engine Control Module (ECM) for the Engine. The ECM provides the information: Engine Warm to the Transmission Control Module (TCM) when the ECM measures a temperature higher than 70°C (158°F).
- The information is provided using a wire between the ECM terminal A9 and the TCM terminal D14. When the Engine is warm the ECM connects its terminal A9 to ground using a Low Side Driver. When the Engine is cold the ECM lets this wire open and the TCM pulls it up to 5 volts.
- When the Ignition is "ON" and Engine is "OFF": the ECM always sends the information "Engine cold" even if the Engine is warm. The information is valid only when the Engine is "ON".

Diagnostic Aids
- This diagnostic test is not an electrical test done by the TCM but a test between different information ("logic test").

- Detection Conditions of Engine Always Cold:
a. Engine seen as cold: wire short to voltage oil open.
b. Transmission Oil Temperature more 100°C (212°F) or more than 20 minutes since last ignition cycle.
c. Detection conditions need to be present for a least 6 seconds.

- Detection Conditions of Engine Always Warm:
a. Engine seen as warm: wire short to ground.
b. Transmission Oil Temperature less than 0°C (32°F).
c. Without problem on Transmission Temperature sensor then: voltage on the Temperature sensor is less than 4.74 V.
d. Detection conditions need to be present for a least 6 seconds.

- Action After the Detection Time:
- No action.

- Recovery Conditions:
- To recover, Engine Coolant Temperature change information needs to be present for more than 6 seconds.

- This DTC can be set when there is no problem at all. This is due to the fact that when the Engine stalls, the Ignition is still "ON", then Engine Control Module provides a false information: Engine cold. The Transmission Control Module, knowing that the last Ignition cycle happened more than 20 minutes ago, then sets DTC 51.

- Using the Scan Tool you can check with TECH 1:
- FO: ENG. TEMP. SW information. When the Engine is cold or when the Engine is "OFF" the TECH 1 should show: Cold. When the Engine is warm the TECH 1 should show Warm.

- This DTC is not very important. In the worst case if would not allow the Torque Converter Clutch (TCC) to be applied. This will cause a low fuel economy.





DTC 51 / Flow Chart