For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0800: Active Transfer Case (ATC) Control Module Requested MIL Illumination

### Circuit/System Description

This diagnostic trouble code (DTC) indicates that an emission related transmission DTC set in the active transfer case control module (ATC). The engine control module (ECM) receives the ATC information over the serial data circuit. The ECM turns ON the malfunction indicator lamp (MIL) when the ATC sends a message over the serial data circuit requesting MIL illumination.

### Conditions for Running the DTC

• | The ignition is ON or the engine is operating.

• | The DTC runs continuously once the above condition is met.

### Conditions for Setting the DTC

The ECM receives a serial data message, from the ATC, in order to illuminate the MIL.

### Action Taken When the DTC Sets

DTC P0800 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P0800 is a Type A DTC.

### Circuit/System Verification

Important: Correct any Engine Controls DTCs before diagnosing TCM DTCs.

DTC P0800 is an informational DTC. If there are no Engine Controls DTCs, refer to Diagnostic Trouble Code (DTC) List - Vehicle for diagnosis of DTCs.