In order for a theft deterrent vehicle to run, a password is communicated between the body function control (BFC) and the powertrain control module (PCM). If a PCM is replaced, the new PCM needs to learn the correct password of the vehicle. When the new PCM is installed, the EEPROM calibration is flashed into the new PCM and the vehicle will learn the new password upon the initial ignition ON cycle. If the BFC is replaced, the PCM needs to learn the new password from the BFC. The Password Learn Procedure is as follows:

1. Attempt to start the vehicle. The vehicle will stall.
2. Leave the ignition ON until the Theft System telltale turns OFF in approximately 10 minutes.
3. Turn OFF the ignition.
4. Attempt to the start vehicle. The vehicle will start on this attempt. The password is now learned.

Attempting to start the vehicle by bypassing the Theft Deterrent System or substituting parts without performing the password learn procedure may set a DTC P1631.

If no password is received a DTCs P1626, and P1631 may be set.