Question about C4 Corvette Dash Readings

[tinmanSC]

Looking for all you C4 vette fans out there! Need some help with the dash electronics. 1991 C4 L98 auto with 55K on the clock. Just replaced the water pump (what a job!), and a few incidentals. Runs and drives pretty well. Been having this problem for a few years, figure it was about time I asked about it. I've searched and search, cannot find anything relevant. When driving around as normal, the dash switches from mph to km/h incessantly. It never switches from km/h to mph, only the other way around. If it's displaying km/h it will happily stay there forever. When I manually switch it to mph using the eng/metric button, it will switch back within a minute or so to km/h.

At first I thought it was just the button acting up, but if it were the button it would sometimes switch from km/h to mph, but it does not. Is there a default setting that gets programmed somewhere that I'm missing? Does it switch back to it's default after a minute or so? If so, where is it?

 

[Boomer]

1. Quit driving in Canada!!!

2. It is part of a worldwide Communist conspiracy to push the metric system.

3. Part of a BITOG conspiracy to make higher numbers come up faster so you do more oil changes.

 

[quint]

I never had this problem when I had my C4, but hanging out on the various Vette forums I did see this specific problem come up time to time. Never did see what the cure was though. I would assume you will end up having to pull the trim off the dash and checking that button for a stuck or bad contact. Mine always worked fine so I never had to mess with it.

 

[tinmanSC]

Originally Posted By: Boomer

1. Quit driving in Canada!!!
2. It is part of a worldwide Communist conspiracy to push the metric system.
3. Part of a BITOG conspiracy to make higher numbers come up faster so you do more oil changes.

HA! Had a hard day, this made it a little better.

 

[01rangerxl]

Unfortunately, I'd bet money on the body control module going haywire. It is probably what controls the digital display, but I don't know for sure.

I get asked about body control modules for this generation of Corvette more than any other model of car hands down. C5 would be a close second, everything else a very distant third.

They are no longer available from GM (new or reman), and due to a limited number out there, finding a reman from anyone can be difficult, but probably not impossible. There are probably companies than can refurb the one you have if you can have the car down for a while.

On the other hand, maybe be glad this is the only weird thing the BCM is doing and leave it at that.

 

[Dave Hess]

I wouldn't worry about fixing it.

Just leave it in Km mode.