gm passlock failure? strange symptoms

I just bought a used 2004 Chevy Silverado 2500HD diesel. Sometimes while driving, the Passlock or Theft system light came on (looks like a padlock over a vehicle, on the left side of the instrument panel), and the battery light came on, and the oil pressure, engine temperature, and fuel level gauges dropped to zero. Also, the trip odometer freezes at whatever mileage was present at the time of failure. It can be reset to zero by pushing the reset knob, though.

It will restart even during this failure mode. Often the restart will clear the failure. Yesterday it did not clear it, but as I say, it started anyway. This morning it was cleared.

I bought it from a Chevy dealer and I thought it was strange that it only had a hardware store key and no keyless fobs. So I had them give me a second key, which they cut, and two new programmed fobs. The failure has occurred with each of the two keys.

Who loses all their regular keys and fobs? I'm guessing it's a repo. I mention this because maybe something has been done to the ignition switch and this is causing the problem. I have no idea. BTW I saw the Carfax and there is no indication of anything unusual like a repo. But maybe they don't show up. OTOH it had a business owner so maybe several people drove it and keys/fobs got lost. Just some data for thought.

I don't want to start throwing money at this. I was thinking of doing the solder a resistor bypass thingy to eliminate the ignition switch as a possibility. But now I'm thinking, if it restarts, it can't be the Passlock. Or can it???

I have no way of pulling codes. Should I break down and take it to a shop to get the codes pulled?

Suggestions most welcome!

if it was a passlock issue, you would not get any start at all. there must be another issue. you should definitly get it checked out to see what codes come up.

It could be a problem with your ignition switch it is very common in gms that the switches have problems. If you start the car with the key if you wiggle the key in the cylinder does the problem happen. If so you coul have a bad ignition switch

Surprise, surprise a Gm dealer that thinks the problem caused by something aftermarket.  Maybe they should go to some of there own training courses, or read TSB.  As above most likely the ingition switch, ing 1 is dropping out.  Could also be the relay.

I got my problem solved a few months ago at an independent shop.  Communications were being interrupted.  He suspected the body control module.  He did a lot of testing, unplugging modules, the dashboard, etc.  He never found anything failed, but all of his unplugging and plugging fixed the problem.  It's been good since then. 

Check for service bulletin on gauges. Did the same thing on my 2004 crew cab 1500. Took to dealer just in time, its a free swap before 65,000. If its over then its out of pocket expense. GM had problems with the gauge assembly, they put in a rebuilt one.
BTW the dealer tried to blame my recently installed python 990, and jvc dd unit. But I had the proof with info printed off the web. Good luck

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