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 P0633: Theft Deterrent Key Not Programmed

### Circuit/System Description

When learning the prerelease 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 when the engine is successfully started. 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.

DTC P0633 will clear upon a successful engine start. Any malfunction that will cause a no-start condition will prevent DTC P0633 from clearing. Prior to diagnosing DTC P0633, ensure that all power moding and engine control systems are operating properly and all conditions that may cause a no-start have been corrected.

1. Ignition in the CRANK position, verify the scan tool Ignition Run/Crank parameter is Active.

⇒ | If not the specified value, refer to Power Mode Mismatch .

2. Perform the 10-Minute Immobilizer Relearn procedure. Refer to Immobilizer System Component Programming . The ECM should successfully complete the password learn and the vehicle should start.

⇒ | If the ECM does not complete the learn or vehicle starting remains disabled, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming