'94 Grand Am, upgraded cluster causing check engine light

[schlicky13]

OK, this one is a little odd for me. My little brother has a '94 Grand Am SE, 2.3l quad sohc, 5spd manual tranny. I've done all the repairs to it but have been stumped by one thing. A couple years ago I pulled the motor and tranny from a junked '95 Grand Am GT (2.3l DOHC, automatic) for a guy, and as payment, he let me keep any other parts from the car that I wanted. Needless to say I picked it clean.

One of the things I kept was the instrument cluster. My brothers car had the base version of the cluster, just a speedometer, fuel gauge and a bunch of idiot lights. The one I pulled from the other car had the better cluster, speedometer, tachometer, fuel gauge, oil pressure, water temp, and voltmeter. The two clusters had nearly identical mileage on the odometers, so I swapped the better instrument cluster into my brothers car. It was a direct plug and play, and everything worked except the oil pressure gauge (turns out they used a different sending unit depending on the instrument cluster, once I switched that it worked fine).

I've been slowly but surely fixing everything on the car and had finally reached a point where I was certain I should no longer be getting a check engine soon light on the dash, but it still comes on. (To be fair, it had always been coming on since he bought the car). '94 and '95 it turns out are oddball, transition years for the Grand Am ODB system, and I had no way of checking the codes (it's essentially an ODB2 system, with an ODB1 style ALDL connector).

I took it to my uncles shop and once they got done playing with it they asked me if the shift light worked. I told them it did, but that was the old dash, (not having a tach, it just had a light that came on letting you know that you needed to either upshift or downshift depending on load and rpm's). The upgraded dash doesn't have that light, I assume, because it has a tach and doesn't need it, (although I suppose it could have the light, if it came from a manual car, but the car I removed it from was an automatic).

They told me that the only code that came up was for the shift light, but they were unable to test it. When they commanded it to turn on, it failed (since I believe it isn't present in this cluster) and they weren't able to go any further. The code they were getting was 27 QDM Fault B, if that means anything to anyone.

So I'm guessing that there must be a slight difference in the programming of the chip in the ECM depending on which instrument cluster the car had. Does anyone have any idea what to do about this? It's not a serious problem, but I'd like to be able to get rid of the code so that if there is something actually wrong, I'll know it when the check engine light goes on. Is there some way to disable this? Or bypass the circuit, or somehow fool the ECM into thinking the shift light is working?

Worst case scenario I can swap the other cluster back in, but I prefer having the upgraded one since it gives so much more information. Or did the upgraded cluster still have the shift light if it was in a car with a manual tranny? Meaning I could try to find one of those and swap it in. Maybe I could get an ECM chip from a car that was a manual and did have the upgraded cluster? Anyways, just a little bit of a head scratcher for me. I've upgraded gauge clusters before in other cars and I've never really had any problems doing that before until this car. Any help or info will be much appreciated.

 

[schlicky13]

Potentially stupid solution

Turns out this seemingly complicated problem may in fact have a stupid solution: just put a light bulb in it. I recently got the car back (the kid that bought it already roasted the clutch in it, I agreed to replace it on his dime, which at my rates will save him a fortune compared to taking it to a regular shop, but now I know why they charge so much, these trannies are a royal PITA to remove and even worse to reinstall).

Anyways, the clutch is done and the tranny is back in but I had to order a new transmission mount bushing to replace the damaged one that I further destroyed trying to get apart, so while I wait for that I decided to revisit the SES light, shift light error code problem. While flipping through the owners manual I discovered that the optional instrument cluster that does have a tach, still has a shift light even though it's redundant. Knowing that the cluster I installed came out of a car with an automatic, I thought maybe the assembly line never installed the bulb to save a few pennies on the cost.

So I went ahead with the annoying task of pulling all the dash panels off so I could get to the cluster, pulled it out, found a few empty light socket holes, shined a light through them to find the spot for the shift light and installed one I had saved from the original cluster. Now, since I still don't have the car operational/functional I can't actually test it yet, so it'll be a few days and then I can see if it fixes the problem. If the SES light doesn't go away, I may run it back out to my uncle's shop again so he can hook it up to his fancy diagnostic machine and see what's really tripping it and go from there.

I'll post an update once I can drive the car and see what it does. And in the end, the ridiculous volume that I've written may not be helpful to anyone, but if helps out one or two people, then that's cool. If nothing else, I'll at least have the satisfaction of knowing that I solved it, even though it was kind of dumb all along.

BTW, almost all the bulbs in these clusters use the same size socket with I think a #194 or #168 bulb, but a couple spots use a smaller socket and bulb (of which I don't know the part number offhand), which is what the optional cluster uses for the shift light. (The original cluster had the standard socket and #194/168 bulb for the shift light).

 

[melsg5]

thanks for the post and the simple solution

 

[schlicky13]

Incomplete test was OK

Got the car back together last night (clutch replacement), backed it out of the shop and the check engine light hadn't come on yet but I can't remember if it normally came on right away, or not until the computer would trip the shift light. Anyways, the car worked fine for about 20ft and as I was cutting the wheel to line up with the exit from the lot, it stopped moving and started making a chattering noise. Did that in every gear and would not move. Pushed it back into the shop, threw it back on the lift and took about 30 seconds to find the problem, the CV axle failed on the passenger side. Really? Really? Just what I needed, but to be fair I had been suspicious of it before, it would make an intermittent howling and when I removed it I could feel the joint easily popping out inside the boot, but I popped it back in and figured I'd see what happens. Dumb idea apparently, so the final verdict on the light bulb fix will be delayed another couple days while I track down an axle or parts to rebuild it.

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[Kevlar]

Schlicky, good post! Nicely written, I appreciate the paragraphs, they make reading so much easier. It was a good read, you kept my interest through it and I'm looking forward to reading your conclusion. I wish you well!

Good job!