Recently the passlock light has become illuminated randomly while driving down the highway. Nothing else out of the ordinary has occured in those instances. It stays illuminated until I shut the vehicle off and does not light up when the vehicle is started again. Anytime random electrical things occur I think battery terminals which I will be checking today. Anyone have any other suggestions?

06 3.5, optima red top, stock terminals

 

Could be the BCM. Mine did that 3 years ago when I got it new. The BCM was replaced and it has not done it since.

 

Try the relearn procedure.

1. First, insert the ignition key and turn the ignition switch to the “On” position (Do not start the engine). Leave the switch on for 11 minutes. The security light may flash or be on steady during this 11 minute period. Make sure the light is no longer on or flashing before proceeding to #2 .
2. Turn the ignition switch off for 30 seconds.
3. Turn the ignition switch to the “On” position (as in step #1) for 11 minutes again.
4. Turn the ignition switch off for another 30 seconds.
5. Turn the ignition switch to the “On” position for 11 minutes a third time.
6. Turn the ignition switch off for 30 seconds one final time.
7. Turn the ignition switch to the “On” position one final time and wait 30 seconds.
8. Attempt to start the engine. If the engine starts and runs normally, the relearn is complete. If the engine does not start, check for trouble codes and address them before attempting the relearn procedure again.

Most common problem is the Passlock sensor. The sensor is part of the ignition lock cylinder on Passlock I and Passlock II systems.

Also read the TSB I posted the "starter relay" thread:

https://www.hummerforums.com/forum/h...r-relay-28273/

TSB 09-06-03-004

2005-09
All Vehicles - Diagnosing and repairing fretting corrosion
Do this--- Disconnect affected connector and apply lube
Dont do this--- Don't replace modules without duplicating condition
09-06-03-004

Check the BCM & PCM connectors & lube.. GL