Chevrolet Trax: DTC P1677: Immobilizer system disabled

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 P1677

Immobilizer System Disabled

Circuit/System Description

The body control module (BCM) sends the pre-release information to the engine control module (ECM) via the serial data circuit. The ECM then sends a challenge to the BCM. Both the ECM and BCM perform a calculation on this challenge. If the calculated response from the BCM equals the calculation performed by the ECM, the ECM will allow vehicle starting. The BCM follows this action by sending the remaining immobilizer data to the ECM. If the immobilizer data sent by the BCM matches that stored by the ECM, the ECM will allow the engine to remain running.

Conditions for Running the DTC

Ignition is in the ACCESSORY or RUN position.

Conditions for Setting the DTC

The ECM is in a reset state or is not programmed properly.

Action Taken When the DTC Sets

• The security indicator in the instrument cluster will illuminate.
• Vehicle starting will be disabled.

Conditions for Clearing the DTC

• A current DTC will be cleared upon the successful programming of the ECM.
• A history DTC will be cleared after 40 malfunction-free ignition cycles.

Reference Information

Schematic Reference

Immobilizer Schematics (Encore), Immobilizer Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

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

Control Module References

Circuit/System Verification

1. Verify there are no immobilizer DTCs set in the K9 Body Control Module.

• If any immobilizer DTCs are set in the K9 Body Control Module

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

• If no immobilizer DTCs are set in the K9 Body Control Module

2. Perform the K20 Engine Control Module immobilizer learn using the engine control module IMMO Learn in SPS. Refer to Immobilizer System Component Programming.
3. Verify the engine starts after the K20 Engine Control Module completes the learn procedure.

• If the engine does not start

Replace the K20 Engine Control Module.

• If the engine starts

4. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for engine control module replacement, programming, and setup.

SYMPTOMS - IMMOBILIZER

IMPORTANT: The following steps must be completed before using the symptom tables.

1. Perform the Diagnostic System Check - Vehicle before using the symptom tables in order to verify that all of the following are true:

• There are no DTCs set.
• The control modules can communicate via the serial data links.

2. Review the system operation in order to familiarize yourself with the system functions. Refer to Immobilizer Description and Operation.

Visual/Physical Inspection

• Inspect for aftermarket devices which could affect the operation of the systems. Refer to Checking Aftermarket Accessories .
• Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to OnStar Stolen Vehicle Slowdown Active to diagnose the symptom.

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