Hi all, ive got an 03 with an oddball electerical gremlin that ive been trying to chase. When I go to start it both the fuel gauge and oil pressure gauge go to zero. I'll get both a "check gauges" and a "reduced engine power" warning on the dash. Ive also had one instance where after idiling for a few minutes both those gauges die and the same warning lights appear. After about 5 seconds every time though, gauges come back and everything goes back to normal. On top of this I get the occasional security light which goes away most of the time after restarting. Both fuel and oil pressure sending units check out ok which has lead me to believe that this might be something related to the ignition switch. Was hoping someone might have some insight before I start tearing into my ignition. Much appreciated.

EDIT: Ive also went ahead and cleared codes to see if any come on when this issue happens. It looks like I got a U1016 code on TCS, SDM, RADIO, both a 1016 and 1000 code on BO-RFA, both a 1016 and 1096 on both door modules and a 1096 code on SDM

Solution: So after a bunch of digging and volt testing I found that of all things it was the hvac module. Looks like it had an aftermarket/rebuilt module put in at some point in its life which was sucking voltage on startup. This caused a voltage drop accross the rest of the system leading to an error within the pcm. Truthfully im not sure about the exact reasoning behind this issue but a replacement of the hvac module cleared everything up. Gotta love early 2000s GM electerical.

 

Sounds like the classic serial data bus issue…does the car start when all this happens ??…if a no crank or a start and stall you can follow this guide below…the connector located within the rubber “accordion” boot when you open the drivers door has issues which can cause this…an auto electric shop can help if this is over your head…good to have a scan tool and DMM to do the testing.





1) Locate the 2 Star Connectors to the left of the BCM and remove the buss bar or “comb” from star connector #2…it has 4 wires on it…see if the car starts…if no start go to next step.

2) Now remove the comb off the other star connector leaving both combs removed…make a jumper wire and jumper the BCM to PCM…light green to dark green wire….if car starts you have a module other than the BCM and PCM on star connector #1 pulling the data bus down….if car still doesn’t start the module pulling the bus down is either the BCM or PCM…go to next step.

3) Take your jumper wire and connect from the purple wire (data bus wire) to the PCM (dark green wire)…now with your scan tool see if you can communicate with the PCM…if you can now communicate the PCM is good and issue may be the BCM…to see if the BCM is indeed bad take the jumper wire and connect the jumper now to the BCM (light green)…with a scan tool that can communicate with ALL modules (NOT a code reader) and if you can’t communicate we can “assume” BCM is bad…for single module “no comm” you want to check the powers and grounds to that module.

 

Would this be exclusively a no crank no start issue? it seems to turn over just fine and I dont get any stumbling while its idiling.

 

If it starts and idles you will need a factory level scan tool to see what module or modules you can’t communicate with and take it from there…unfortunately we can’t diagnose this for you over the internet…you can at least check for any trouble codes mainly “U” or communication codes from the DIC if you don’t have a scan tool.

 

I had similar issues with mine a few years ago, would kill every now and then, I changed the ignition switch, not a bad job, maybe 30 minutes to and hour if you have never taken any of that apart.
it's cheap enough to give it a shot.

 

My fuel gauge and volt meter were extremely slow to respond — in addition to other IPC issues. In my case a replacement IPC motherboard was necessary to cure the issues.