P1631

DTC P1631

Circuit Description

When the ignition is turned ON, the key is tested by the immobilizer anti-theft system. While the key code is being read by the immobilizer control unit, the engine can start and run with any key that will turn the lock cylinder. The key code is read and compared with key codes that have been stored in the memory of the immobilizer control unit. If a valid key is detected, the immobilizer control unit sends a serial data release message to the electronic control module (ECM). Included in the release message is an identification (ID) code which assures that neither the immobilizer control unit nor the ECM has been substituted to defeat the system. If the ECM receives an invalid release message, the ECM disables the fuel injector circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1631 Theft Deterrent Start Enable Signal Not Correct

Conditions for Setting the DTC

* The ECM does not receive the signal from the immobilizer control module within 1.260 seconds after the ignition is turned ON.
* The above conditions are maintained until the ignition is switched OFF.

Conditions for Clearing the MIL/DTC

The ignition switch is turned OFF or the scan tool TROUBLE CODE CLEAR command is issued.