For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using the 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 P0633: Theft Deterrent Key Not Programmed

### Circuit/System Description

When learning the fuel enable password, as well as the challenge and response sequence, the engine control module (ECM) is placed in learn mode. DTC P0633 will set automatically as an indicator that the system is in learn mode and not as a fault indicator. Once the password and challenge/response are learned, learn mode will be exited and the DTC cleared. If the ECM does not exit learn mode, P0633 will remain current and indicate a fault.

### Conditions for Running the DTC

The ECM is in learn mode.

### Conditions for Setting the DTC

DTC P0633 will set any time the ECM enters learn mode.

### Action Taken When the DTC Sets

The security indicator will illuminate.

### Conditions for Clearing the DTC

• | A current DTC P0633 will be cleared upon a successful engine start after exit of learn mode.

• | A history DTC will be cleared after 100 malfunction-free ignition cycles or when a scan tool is used to clear DTCs.

### Diagnostic Aids

The "key" referenced in the DTC descriptor does not refer to the vehicle key. In this case, "key" is referring to the challenge response.

### Reference Information

#### Schematic Reference

Immobilizer Schematics

#### Connector End View Reference

Immobilizer Connector End Views

#### Description and Operation

Immobilizer Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Important: Because of normal system communications between the TDM and ECM, any theft deterrent B-codes must be diagnosed prior to the diagnosis of P-codes.

Perform the Programming Theft Deterrent System Components procedure. Refer to Control Module References

⇒ | If the ECM does not exit learn mode after the programming attempt, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification

Control Module References