For 1990-2009 cars
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

### Circuit Description

Engine coolant temperature information is sent to the transmission control module (TCM) by the engine control module (ECM) through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P1792 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P1792.

When the ECM sends the TCM an engine coolant temperature signal that is below the lower limit, above the upper limit, or is an unreliable value, then DTC P1792 will set. DTC P1792 is a type C DTC.

### Condition for Running the DTC

The ignition is ON.

### Condition for Setting the DTC

Engine coolant temperature signal is below the lower limit, above the upper limit, or is an unreliable value for 1 second.

### Action Taken When the DTC Sets

• | The MIL will not illuminate.

• | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM records this information as Failure Records.

• | The TCM stores DTC P1792 in TCM history.

### Conditions for Clearing the MIL/DTC

• | A scan tool can clear the DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.

• | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission
2 |

1. Install the Scan Tool .
2. Turn ON the ignition with the engine OFF.

Important: Record all Failure Records before clearing the DTC. Using Clear Info erases the Failure Records from the ECM and TCM.

3. Record the DTC Failure Records.

Did you record any ECM Failure Records?

--

Go to the applicable ECM DTC

Go to Step 3

3 | Did you record Failure Records for any of the following DTCs?

• | DTC U2100

• | DTC U2104

• | DTC U2105

• | DTC U2108

--

Go to the applicable CAN Bus DTC

Go to Step 4

4 |

1. Clear the DTC.
2. Turn the ignition OFF for at least 30 seconds.
3. Start the engine and allow it to idle for 2 minutes.

Did DTC P1792 reset?

--

Go to Step 5

Go to Intermittent Conditions in Engine Controls

5 | Did any other DTCs set? | -- | Go to the applicable DTC | Go to Step 6
6 | Replace the ECM. Refer to Engine Control Module Replacement . Is the action complete? | -- | Go to Step 7 | --
7 | Perform the following operation to verify the repair:

1. Select DTC on the scan tool.
2. Select Clear Info.
3. Start the engine and allow it to idle for 2 minutes.

Did DTC P1792 reset?

--

Go to Step 1

System OK