Help! 1990 Electronic Display Blank Once Engine Is Started

[MarkWD]

I'm at a total loss over this one. I've had idling problems with my L98 and took it to Pep Boys. They said the throttle arm was slightly bend (though that seems impossible), fixed it, and now it is better, although the automatic choke does not seem to function. Regardless, when I started the engine at Pep Boys, the display blanks out after the engine is started. I showed them and they shrugged, saying they don't see how they could have affected it. Since then I've seen C-12 code (which shows there isn't a problem), then 1.0 with three dashes to 4. to 1.0. I've checked all of the fuses and they are fine. It displays properly before start and after engine shutdown, but not while it's running. The latest code I saw was H41 then 1.0 to 4. to 1.0. I've wasted a ton of money at the dealership trying to resolve other issues with no success. It has to be something simple. ANY help would be greatly appreciated.

 

[Otter]

I'm at a total loss over this one. I've had idling problems with my L98 and took it to Pep Boys. They said the throttle arm was slightly bend (though that seems impossible), fixed it, and now it is better, although the automatic choke does not seem to function. Regardless, when I started the engine at Pep Boys, the display blanks out after the engine is started. I showed them and they shrugged, saying they don't see how they could have affected it. Since then I've seen C-12 code (which shows there isn't a problem), then 1.0 with three dashes to 4. to 1.0. I've checked all of the fuses and they are fine. It displays properly before start and after engine shutdown, but not while it's running. The latest code I saw was H41 then 1.0 to 4. to 1.0. I've wasted a ton of money at the dealership trying to resolve other issues with no success. It has to be something simple. ANY help would be greatly appreciated.

Had that problem on an 89 I had, read a lot, asked around for a fix, then, after a couple weeks, I rapped a couple times on the display with my knuckles and it lit back up. Never had the problem again. Hope you would be as lucky.

 

[MarkWD]

No one home

Thanks for the suggestion. Sometimes if you can't fix something you just need a bigger hammer. Unfortunately, in spite of my knocking, nobody's home. I did get the H41 code before starting this time, and the screen went blank once it was started. I can drive it using Waze guidance, but it's not a good way to drive. Hopefully there will be other ideas. I do appreciate the help.

 

[Hib Halverson]

If you saw H41 that's a history code for loss of ECM serial data. Without seeing the car, my wild-assed guess is you have a wiring and connections problem somewhere between the ECM and the IP display which is causing the IP display to loose the signal from the ECM. There also a chance the problem may be in the ECM itself but that's less likely than a wires/connections problem.

Going to Pep Boys with that problem is a fool's errand. It's highly unlikely that any Pep Boys service center is going to have the C4 diagnostic chops to solve that. You need to find a service facility familiar with Corvette electrical work.

If you are an intermediate or better DIY, you might be able to track the problem down yourself but doing so will require the right tools, a factory service manual and the willingness to pull the dash apart, if necessary.

 

[MarkWD]

Many thanks

Thank you so much for the reply. Yes, Pep Boys is not a go-to shop for Corvettes. I ended up there because the engine wouldn't start and went back because it wouldn't idle. There doesn't appear to be anything obvious in the wiring, but I'll continue to investigate. I've had this car for 18.5 years and while there have been other electrical issues, this one is a first. I learned the hard way that many Corvette Chevrolet mechanics don't know much, and are also independent contractors. In other words, if you take it back, the dealership takes the money from their mechanic's pocket. The more complex a vehicle, the more difficult it is to resolve issues when they get older.

 

[mike77]

There was a recall bulletin issued by GM # 90C07 regarding IP wire rub thru at the hood release cable bracket. may be something to look at.
Mike

 

[MarkWD]

thank you

Thanks, Mike. I was not aware of that, and I'm sure GM has no way to honor it at this point, but it's definitely something to check. I appreciate the tip!

 

[mike77]

Actually the recalls do not expire. "IF" your car fall in the serial number range and the recall has not been completed on your car, they are required to address the problem. However there are a few if's, one being" is that the problem". Recall TSB 90C07. serial # range L5100001-L5103172, L5800001-L5800227.

Mike