Help - no speedo

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Apr 15, 2009 | 11:08 AM

jdfrank

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Help - no speedo

I have a 1990 Corvette that for the life of me I can't figure out why the electronic speedo, trip meter, gas gauge, etc is not working. I cleaned up all the electrical connections at the battery and pulled the seat belt sensor and cleaned it under the battery box, cleaned all the grounds put it all back together, followed the instructions for resetting the air bag light, all the mechanical gauges work and the speedo did for a while now it is not. I pulled the codes and the machine didn't read any, please help as you know with the Vette you can go from zero to speeding ticket in no time so I need help before the CHiP's nail me.

Regards,

Jdfrank

PS: make it easy as so far nothing I have done has been easy on fixing the car.

Apr 15, 2009 | 04:20 PM

pcolt94

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From: Orlando FL

Those years have internal connection problems on the instrument cluster.

But did you have the problem before or after you did the work you indicated in your post?

In the mean time keep the tank full and get a GPS.

Apr 17, 2009 | 12:15 AM

jdfrank

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When I got the car it didn't work, the battery had been dead and they had been jumping the car to get it started. I replaced the battery cables at that time and put in a new fusable link and a new battery. I started the car and it worked fine. Then I followed the instructions to get the air bag light off and when I completed the fix the speedo didn't work then I disconnected the battery cable, reconnected and then it started working. A couple months later I go to start it and I got 888 on the speedo and same with the odometer and nothing else worked either. I guess I can disassemble the dash and clean the connection to the speedo and see if that works?

Jdfrank

Apr 17, 2009 | 02:58 AM

WVZR-1

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I believe before I did the disassembly and clean I would find someone with a Tech1, a Tech2 or a quality scanning device that can read "functions" from the ALDL connection. Just a "WAG" here but if you get results from the ALDL then I'd consider checking into the connections. BUT I would think that since you've done substantial work in the vicinity of the ECM you've maybe fractured a wire or pulled a wire from a connector at the ECM. I believe (guess here) that on a '90 the speed sensor signal goes to the ECM and is then distributed from there to the CCM and the cluster.

Have you done considerable work "under the dash" near the DERM while working on your SIR lamps?

Do you have a FSM?

Last edited by WVZR-1; Apr 17, 2009 at 03:58 AM.

Apr 17, 2009 | 11:19 PM

twin540

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From: San Antonio TX

I have that problem with my 91 , I take the cluster out take it apart and tighten all the bolts in the back of the cluster reassemble and problem well go away. You can also tap on the custer see if you can get it to flicker.

Apr 18, 2009 | 11:59 AM

jdfrank

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I have tried tapping but to no avail, I am going to pull the panel tomorrow and go through and tighted everything, It has got to be a simple fix. I used an OBD 1 tester as mentioned previously and it pulled no codes. I started to pull the dash yesterday but had to stop and put it back together as it has become my daily driver, oh me, but while I was up there I found a connector coming off the connector for the OBD and it looks like a straight pin connector for something, do you have a clue.

Thanks.
Jdfrank

Apr 18, 2009 | 01:04 PM

WVZR-1

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I really believe that before I tore into the cluster I'd check the ECM pin-outs. There's I believe two (low & high) to the ECM from the VSS and a single out to the CCM that distributes the signal to the cluster, cruise and the variable audio of the radio. I believe it would be the red connector pin 8. As much as you were doing in the vicinity of the ECM anyway you could have destroyed a ground and there are several in the vicinity.

I guess a "simple" test might be this. If the cruise and the speed compensated volume worked before you could drive the car. If both the cruise and the SCV now don't work your wasting your time tearing into the cluster. My thoughts could be 100% in error but I'd sure like to try it the "easy way" first!

I would think maybe a test light from pin 8 to ground might light if there were a signal leaving the ECM. If there's nothing leaving then it could be either maybe the low or high signal from the VSS at the ECM.

Apr 19, 2009 | 01:01 PM

jdfrank

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The cruise control didn't work when I bought the car but I will go through the area I worked on and recheck all the grounds. I also did some relooming so I will pull the looming and check to see if I did any damage. Thanks for you patience in helping with this issue. I am not to keen on all the terms such a scv or ccm but I do know the term ecm and I will check with the chilton and haynes which are both weak on the electronic sections in their manuals.

jdfrank