Refer to Engine Controls Schematics .
Circuit Description
The vehicle theft deterrent system, is designed to prevent vehicle theft by disabling the engine unless the lock cylinder is correctly engaged by a mechanical key. The theft deterrent system utilizes four components for theft detection, the lock cylinder, ignition switch, the body function controller (BFC) and the Powertrain Control Module (PCM).
When starting the engine, the PCM looks for a password from the BFC through the Class II serial data circuit. If the password is not recognized or not present, the PCM will disable the engine. There are 2 modes of tamper detection:
| • | No password received. The engine will start and stall quickly. The THEFT SYSTEM telltale will flash on the instrument panel cluster (IPC). |
| • | Incorrect or disable password received (more than 3 invalid passwords received). The engine is disabled for at least 10 minutes and the THEFT SYSTEM telltale will illuminate solid on the IPC for the 10 minutes. |
After the vehicle has passed theft detection, the PCM will continue normal engine operation. Additional information can be found in Theft Deterrent.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | An unrecognized password or no password is sent to the PCM from the BFC. |
| • | The condition is present for less than 1 second. |
Action Taken When the DTC Sets
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Attempting to start the vehicle by bypassing the theft deterrent system or substituting parts without performing the password learn procedure may set a DTC P1631.
If no password is received P1626 and P1630 may be set.
If the serial data loss occurred after a good theft password has been received, the PCM must be reprogrammed and the password learn and the crankshaft position variation learn procedures must be completed to allow the theft system to operate properly. Refer to Powertrain Control Module Replacement/Programming and Crankshaft Position System Variation Learn and Body Control Module (BCM) Programming/RPO Configuration for reprogramming procedures.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain OBD System Check? | -- | ||
2 | Perform the password learn procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in body control module. Can the password learn procedure be performed successfully? | -- | System OK | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent |
