New to the C4 world and now having problems.I recently bought a 1992 C4.

When I purchased the car, the INFL REST was on all the time. The previous owner told me that he had OHM'd out the air bag sensors and they checked out. But he also told me he was getting a short to ground (not sure what he meant by that) and he replace the air bag module. OK, everything else worked and the car drove fine so I ignored it. The other day, before I replaced the battery, I had read on the forum that there could be rust under the sensors and that may be why the INFL REST was on. I unbolted the right sensor, cleaned the frame & sensor, put dielectric grease on it and bolted it back in. Connected the battery and the car started no problem but the INFL REST was still on.

Yesterday, I unhooked the battery, removed the fuse and unbolted the left front sensor. Did the same thing, cleaned & put dielectric grease on it and bolted it back in. I then hooked the battery up and tried to start the car. It just turned over, like it wasn't getting any spark or fuel. I realized that I had forgotten to install the fuse, so I put it back in and tried starting the car. Again, just turned over, wouldn't start.

I used a paperclip to read the codes and found the following: C41 then H41. Goes to 4 and shows ERR, goes to 9 and shows ERR. I've tried clearing the codes but obliviously, they won't clear,

I have very limited knowledge of electrical so if someone was to explain what I should do, please explain like you are talking to a child.

Thanks in advance for any/all help

Russ

 

You mentioned the 92 was running fine.
You disconnected the battery. removed fuse. removed 1st AB sensor cleaned, used dieletric grease.
Same with the 2nd AB sensor. Restored fuse and battery. NO start.

PO owner mentioned a short to ground.

It would appear both AB sensors were completing your ground from the frame.
The dielectric grease created a barrier preventing ground. Most likely to the ECU = computer. No spark, no start.
I would start with all of the ground contacts.
Remove clean, wirebrush frame, screws, bolts
I would use stainless star or split washers.
I personally re- tap replace with SAE stainless screws.

 

I agree check all grounds. Make sure clean and tight. Check harness and I’d reseat connectors to make sure they are also clean and tight at the ECM.

if none of this works you may have an ECM issue and may need to get it reflowed by SIA.

Of course it makes sense to follow the FSM troubleshooting guide to make sure there is not a module or wire shorting the serial line etc…. first. The ECM, CCM, ASR etc all set on that comm line. Highly recommend.

Fuses also easy to check per IHBD (no ECM power no start!)

 

So, I back tracked my previous steps and removed all the grease, cleaned the frame, cleaned the bolts and then reinstalled the airbag sensors. I tried doing the procedure of using the paperclip and buttons to try to clear everything but the codes remain. So, even though the battery has been disconnected and the fuse has been pulled, I'll still need to clear the codes using the scanner?

Thanks for any/all help

Russ

 

UPDATE: As I said, I unbolted the right side airbag module, cleaned the dielectric grease off of it, cleaned the frame, cleaned the bolts and reassembled. This morning, I go out and try to start it, only turned over. Remembered I had forgotten to install the airbag fuse and installed it. Tried starting it again, only turned over. Got my paperclip out and started reading the codes...again showing C41 & H41. Damn it!!!!! Then tried clearing the codes, Checked the codes again and only showing C12!!!!! Came on the forum and everyone said that was the only code you wanted to see. Went back out and turned the key and started right up!!!!!!!

Now, the INST REFL is still showing on the control panel. How do I get that to stop showing, short of taking the bulb out?

Thank you everyone that suggested different things, couldn't have done it myself without your help.

Russ

 

https://www.corvetteforum.com/forums...ol-module.html

 

I don't want to get the bulb out, since it could be a problem in a safety device... Maybe it is a bad ground or something not so important.... Tough i would investigate and solve the trouble if car would be mine

 

That's what I would rather do, repair before taking the bulb out. Thank you for the link, reading it, it sounds like it could be just a chaffed wire (hopefully)

I do know that one of the previous owners had been behind the dash, so, who knows what they did back there.

Russ