Home » GM 6.5 » GM/Detroit 6.5L ENGINE CONTROLS – DTC P1631 Theft Deterrent Password Incorrect

GM/Detroit 6.5L ENGINE CONTROLS – DTC P1631 Theft Deterrent Password Incorrect

Circuit Description
This test checks for mismatched (incorrect) passwords between the Passlock module and PCM. Whenever the Passlock module or PCM are replaced, a theft learn procedure must be followed in order for the new password to be learned.

Conditions for Running the DTC
The ignition switch in the ON position.

Conditions for Setting the DTC
An incorrect fuel continue password has been received from the Passlock module.

Action Taken When the DTC Sets
• The VTD system is enabled.
• The vehicle will not start.
• The malfunction indicator lamp (MIL) will not illuminate.

Conditions for Clearing the DTC
• A History DTC clears after forty consecutive warm-up cycl es, if this or any other emission related diagnostic does not report any failures
• The use of a scan tool.

Diagnostic Aids
Refer to Vehicle Theft Deterrent system for further diagnosis.

Test Description
Number(s) below refer to the step number(s) on the diagnostic table.
3. The 10 minute and 30 second time criteria, are a minimum required amount of time. The time limit can exceed this limit, without interfering with the Auto Learn Procedure. A scan tool can be used (VTD Auto Learn Timer equals Inactive) to determine when the 10 minutes has expired.
4. The security lamp will remain ON until 10 minute timer is complete. Depending on the component replaced, the lamp may remain ON steady or flash.
8. If DTC P1631 is set, indicates that the procedure was not followed correctl y. The Re-learn procedure will have to be re-performed.


Leave a Reply

Your email address will not be published. Required fields are marked *