Problem 2 of 3:
The ignition lock cylinder fails to change the voltage on the yellow wire.

Test & Fix:
With the ignition lock cylinder electrically reconnected, back-probe the yellow wire with the positive lead of the voltmeter and connect the negative lead to a known-good ground. Insert the ignition key in the lock cylinder, rotating the key to the start position, then release the key, allowing it to return to the KOEO position.

During the time the key was rotated to the start position then released to the KOEO position, the voltage on the yellow wire should change from 5 volts to a lower value. Because there are 10 different voltage values, we are unable to give a specific voltage value. However, what the voltmeter should indicate is a change in voltage value. If this change in voltage did not take place, replace the ignition lock cylinder. For the theft system relearn procedure, go to step 3.

Problem 3 of 3:
A component related to the theft system, BCM, PCM or ignition lock cylinder has been replaced and the password needs to be re-learned.

Test & Fix:
Password programming can be done using the following procedure:

1. Ensure the vehicle’s battery is fully charged.

2. Use a scan tool to clear any diagnostic trouble codes from the PCM and BCM.

3. Starting with the ignition switch in the Off position, momentarily crank the engine and leave the key in the Run position while observing the security indicator. In 10 minutes the security indicator should turn off. Rotate the key to the Off position for five seconds.

4. Repeat step 3 two more times.

5. The fourth time the engine is cranked, the engine should start and the BCM and PCM will have learned the new password.

6. Clear the BCM and PCM trouble codes again.

Courtesy of Identifix, Inc.