Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
The theft deterrent module (TDM) sends the pre-release password to the engine control module (ECM) via the serial data circuit. The ECM then sends a challange to the TDM. Both the ECM and TDM perform a calculation on this challenge. If the calculated response from the TDM equals the calculation performed by the ECM, the ECM will allow vehicle starting.
Ignition is in the ACCESSORY or RUN position.
The calculated response from the TDM does not equal the calculation performed by the ECM.
• | The security indicator will illuminate. |
• | Vehicle starting will be disabled. |
• | A current DTC P1632 will be when a valid calculation is received. |
• | A history DTC will be cleared after 40 malfunction free ignition cycles or when a scan tool is used to clear DTCs. |
The "key" referenced in the DTC descriptor does not refer to the vehicle key. In this case, "key" is referring to the challenge response.
Theft Deterrent System Schematics
Theft Deterrent System Connector End Views
Vehicle Theft Deterrent (VTD) Description and Operation
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.
Perform the Programming Theft Deterrent System Components procedure. Refer to Programming Theft Deterrent System Components . 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. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, setup, and programming.