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DTC P1648

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 P1648: Theft Deterrent Security Code Incorrect

Circuit/System Description

The immobiliser module or the vehicle theft deterrent (VTD) module sends the fuel enable password to the engine control module (ECM) via the serial data circuit. The ECM then challenges this password. Both the ECM and immobiliser module perform a calculation on this challenge. If the calculated response from the immobiliser module equals the calculation performed by the ECM, the ECM will allow vehicle starting. The ECM will disable vehicle starting if any of the following conditions occur:

    • The fuel enable password is invalid.
    •  The fuel disable password is sent by the immobiliser module.
    •  No passwords are received. - There is no communication with the immobiliser module.
    •  The immobiliser module calculated response to the challenge does not equal the calculation performed by the ECM.

Conditions for Running the DTC
    • The ignition is ON.
    • The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects no immobiliser message ID.

Action Taken When the DTC Sets
    • DTC P1648 is a Type C DTC.
    • Vehicle starting is disabled.

Conditions for Clearing the DTC

DTC P1648 is a Type C DTC.

Reference Information

Schematic Reference

Immobiliser Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Wiring Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Connector Repairs

Circuit/System Verification
  1. Ignition ON, verify that DTC U0167 is not set in the K20 ECM.
    2. ⇒If the DTC sets, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Perform the immobiliser Neutral Mode function by selecting the Module Setup on the scan tool.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the K89 Immobiliser Control Module.
  2. Ignition OFF for 60 seconds, test for infinite resistance between the serial data circuit terminal 6 and ground.
    3. ⇒If less than the specified range, test the serial data circuit for a short to ground.
  3. Ignition ON, test for less than 1V between the serial data circuit terminal 6 and ground.
    4. ⇒If greater than the specified range, test the serial data circuit for a short to voltage.
  4. Ignition OFF, disconnect the harness connector at the K20 ECM.
  5. Ignition OFF, test for less than 5Ω between the serial data circuit terminal 6 of the K89 Immobiliser Control Module and the K20 ECM terminal listed below:
    6. •  K20 ECM terminal 56 (without FX3)
    •  K20 ECM terminal 57 (with FX3)
    ⇒If greater than the specified range, test the serial data circuit for open/high resistance.
  6. If all circuits test normal, replace the K89 Immobiliser Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

   


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