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 P1678: Theft Deterrent System - Incorrect Enviornment IdentificationDTC P1679: Theft Deterrent System - Incorrect Enviornment Identification
Circuit/System Description
When certain modules are programmed and configured during installation, the module learns a specific environment identifier which is unique to the vehicle. The environment identifier is used as a means to discourage vehicle theft by means of swapping modules between vehicles.
The steering column module (CIM) is the keeper of the environment identifier. The engine control module (ECM), instrument panel cluster (IPC), underhood electrical center (UEC), and rear electrical center (REC) each learn the environment identifier during their configuration process. During vehicle operation, each of these modules report their environment identifier to the CIM. The CIM compares the received environment identifiers to its own stored identifier. If the identifiers match, vehicle starting is allowed. If two or more non--matching environment identifiers are received by the CIM, vehicle starting is disabled.
Conditions for Running the DTC
Ignition ON
Conditions for Setting the DTC
An incorrect environment identifier is learned to the ECM
Action Taken When the DTC Sets
| • | Vehicle starting is disabled |
| • | The Service Vehicle Soon indicator will flash |
Conditions for Clearing the DTC
| • | A current DTC will be cleared when the module learns an environment identifier. |
| • | A history DTC will clear after 100 malfunction free ignition cycles. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Immobilizer Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, select Reset ECU on the scan tool for the ECM.
- Perform the Programming and Setup procedure for the ECM. Refer to Control Module References for programming and setup procedures. Verify the DTC does not reset after programming.
Important: When reprogramming a control module which has already been programmed, additional security measures must be met before reprogramming is allowed. Prior to programming, security access must be granted by connecting a Tech 2 in a pass-thru arraignment and requesting security access in TIS. Once security access is granted, the security code must be entered. The security code can be found in DealerWorld. Both of these security measures must be met before the Reset ECU selection is allowed.
| ⇒ | If the DTC resets, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, programming, and setup
