sounds more like an ECM than actual cluster problem.
89 C4 dash cluster problems
Thread Starter
Racer
Joined: Aug 2004
Posts: 417
Likes: 0
From: Audubon PA
89 C4 dash cluster problems
Thank God for this site. My 89 vette had cluster problems. The instant MPG always reads "0" and the average MPG always reads "99".
So I took it to a reputable radio repair shop known in my area for repairing corvette clusters and when I reinstalled the repaired cluster it still has the same MPG problems. Everything else in the cluster works perfectly( speedometer, tach, coolant temp, battery, oil press., oil temp, fuel gauge, and trip odometer work perfectly). Now when I try to reset the average MPG it goes from 99 to 12.8, but in a few seconds after reset it goes back to 99 again, instant MPG still at 0. I'm going to bring cluster back to radio shop for them to re-repair. The BIG question is where is the problem, is it my cluster, can it be a wire or signal that's not getting to the cluster, can it be the connection to the transmission( someone told me that if my speedometer works so to should my MPG),can the problem be the reset cluster. The repair shop has my cluster now, but if they can't fix it where do I go from here???
So I took it to a reputable radio repair shop known in my area for repairing corvette clusters and when I reinstalled the repaired cluster it still has the same MPG problems. Everything else in the cluster works perfectly( speedometer, tach, coolant temp, battery, oil press., oil temp, fuel gauge, and trip odometer work perfectly). Now when I try to reset the average MPG it goes from 99 to 12.8, but in a few seconds after reset it goes back to 99 again, instant MPG still at 0. I'm going to bring cluster back to radio shop for them to re-repair. The BIG question is where is the problem, is it my cluster, can it be a wire or signal that's not getting to the cluster, can it be the connection to the transmission( someone told me that if my speedometer works so to should my MPG),can the problem be the reset cluster. The repair shop has my cluster now, but if they can't fix it where do I go from here???
Last edited by jzvette; Sep 2, 2004 at 12:54 PM. Reason: need quick reply
Melting Slicks
Joined: Apr 2000
Posts: 2,408
Likes: 3
From: Bel Air Md
My 88 gave me some strange readings. Near empty tank had a range of 400+ miles. Plus some other strange things. It also ran very bad. Very rich mixture with black smoke. It turned out to be the computer.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
MPG and Range is sent on the data line from the ECM. It's spliced to the same circuit that goes to the Diagnostic Link, so see if will flash a Code 12. If so, the ECM is usually good, but the line may be open to the cluster, so you will need to check the orange wire from the Diagnostic Link to the splice and back to the Cluster. If it won't flash a Code 12 or if there's no Check Engine Light, the ECM is usually at fault.
Thread Starter
Racer
Joined: Aug 2004
Posts: 417
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From: Audubon PA
SunCr,
Thanks, but what code should I get if ECM bad. I recently had a code 32, but it was a soft code, on and off in a few seconds. Someone said if my speedo works then my MPG should work, what do you think???
Thanks, but what code should I get if ECM bad. I recently had a code 32, but it was a soft code, on and off in a few seconds. Someone said if my speedo works then my MPG should work, what do you think???
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Speedo has nothing to do with it. Fuel and odometer are sent to the ECM and the ECM uses the TPS, Engine Load, MAF,Coolant Temp & RPM to calculate the Avg/Instant. Information is bidirectional; ie, circuit carries info to an from the ECM. Wire is at Cluster PIN D10, orange, spliced to the Diagnostic Link, Cavity E and then to ECM PIN A8. Trying to read voltages on this line are meaningless (though they should cycle between 2 & 5 volts), so a quick check is to see if it will flash a code or you can disconnect the TPS and see if it will generate 22, or checking continuity from the Cluster to Cavity E is another way to see if the wire's good. You can also check for a dead Function Switch. With the switch in the "Off" position, disconnect the cluster harness and then check for continuity between the wire in A5 (Lt Grn) and B1 Ground. Meter should show an open circuit. If so, put the switch in the AVG or INST position and check again. There should be resistance, but if it's zero, the cluster is bad. If it's still open (infinite), the switch is bad.
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Thread Starter
Racer
Joined: Aug 2004
Posts: 417
Likes: 0
From: Audubon PA
SunCr,
Can it still be a problem with the cluster?? I took it back to radio repair shop ( They gave me a 1 year warranty on repairs), so I waiting for a call back from them. I guess I'll know when I get it back, then I can do the tests you offered. Thanks for all the help. jzvette
Can it still be a problem with the cluster?? I took it back to radio repair shop ( They gave me a 1 year warranty on repairs), so I waiting for a call back from them. I guess I'll know when I get it back, then I can do the tests you offered. Thanks for all the help. jzvette
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Tough call, but if the ECM is sending signals (and it is if you can read codes) then something is probably wrong with the Cluster. Either it isn't sending fuel and odometer or something is preventing it from displaying the information it's getting. Assuming the wire is good, then the only thing that I can think of that might be in the way would be the Function Switch. If it's open, you probably wouldn't get any readout; but my info on testing it was wrong. The terminals should be open (infinite) with the switch off; O ohms with the switch on. Any resistance with the switch on would skew the readout, so if there's any resistance with it on INST of AVG, replace the switch.
Thread Starter
Racer
Joined: Aug 2004
Posts: 417
Likes: 0
From: Audubon PA
SunCr,
I'm getting cluster back today, according to radio shop cluster is perfect. So I'm going to check the A5 (lt green) and B1ground for an open/0 ohms/or resistance like you advised to see if I have a bad switch. There are two connectors to the cluster one large, one small, where is the A5 and B1ground located??? Do I just look for a lt green wire?? What color will the ground wire be?? I don't have alot of electical repair experience. If I check these wires and they are functioning properly is the next step a new ECM????
I'm getting cluster back today, according to radio shop cluster is perfect. So I'm going to check the A5 (lt green) and B1ground for an open/0 ohms/or resistance like you advised to see if I have a bad switch. There are two connectors to the cluster one large, one small, where is the A5 and B1ground located??? Do I just look for a lt green wire?? What color will the ground wire be?? I don't have alot of electical repair experience. If I check these wires and they are functioning properly is the next step a new ECM????
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
B1 is black. I rechecked my schematic and here's everything you want to check. For the Fuel, A5. lt.grn, is the reset switch. It should be open unless pressed. A1, brown, is avg fuel rate. B2, Dk green is the inst fuel rate. If the swith is off, all the wires should be open.
For the Odometer, A7, white is Range. Trip is A4 orange. Reset is A3 pink and it should be open unless pressed. All should read open if the switch is off.
If all the switches function, then the only thing left would be the ECM unless the orange wire at D10 is open.
For the Odometer, A7, white is Range. Trip is A4 orange. Reset is A3 pink and it should be open unless pressed. All should read open if the switch is off.
If all the switches function, then the only thing left would be the ECM unless the orange wire at D10 is open.
Thread Starter
Racer
Joined: Aug 2004
Posts: 417
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From: Audubon PA
SunCr,
I tried testing wires at connectors, but there seems to be a problem. No pink wire, I did find the B1 ground and the A5 lt green. When I tested I did get open with swith off, but when you said switch on do you mean the reset switch or the AVG switch?? If switches are good then it must need ECM. I have a 89 vette, I did not see a pink wire. Could your test info be for another year vette?? I really need to know what you mean when you said "0 ohms with swich on" which switch??? (the reset??) Thanks jzvette
I tried testing wires at connectors, but there seems to be a problem. No pink wire, I did find the B1 ground and the A5 lt green. When I tested I did get open with swith off, but when you said switch on do you mean the reset switch or the AVG switch?? If switches are good then it must need ECM. I have a 89 vette, I did not see a pink wire. Could your test info be for another year vette?? I really need to know what you mean when you said "0 ohms with swich on" which switch??? (the reset??) Thanks jzvette
Last edited by jzvette; Sep 9, 2004 at 06:37 PM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Sorry, you're right - Pink is used by the factory to test the Cluster.
Lt Blue, Pin A6 is the Trip Reset.
For Lt Green, Pin A5, it the Fuel Reset circuit. Push the Button and it should should good continuity or 0 Ohms. Same test for the Trip Reset above.
For the other circuits, they should be open with the switch in the off or middle position and then show good continuity or 0 ohms when they're switched to a function, either full up or down.
Lt Blue, Pin A6 is the Trip Reset.
For Lt Green, Pin A5, it the Fuel Reset circuit. Push the Button and it should should good continuity or 0 Ohms. Same test for the Trip Reset above.
For the other circuits, they should be open with the switch in the off or middle position and then show good continuity or 0 ohms when they're switched to a function, either full up or down.
Thread Starter
Racer
Joined: Aug 2004
Posts: 417
Likes: 0
From: Audubon PA
SunCr,
Thanks, I think it's the ECM at this point. I'm not at the car now but I remenber it going to 0 ohms when I hit the reset button. Thanks again for all the help. So it now looks like I have to buy an ECM. Can your recomend where to buy?? (Midamerica) Where is the ECM located (89) and how hard is it to get at. I do know that I should disconnect the battery and that I have to save chip that is in the old ECM. Any other tips you can give me before I do the job. jzvette
Thanks, I think it's the ECM at this point. I'm not at the car now but I remenber it going to 0 ohms when I hit the reset button. Thanks again for all the help. So it now looks like I have to buy an ECM. Can your recomend where to buy?? (Midamerica) Where is the ECM located (89) and how hard is it to get at. I do know that I should disconnect the battery and that I have to save chip that is in the old ECM. Any other tips you can give me before I do the job. jzvette
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Passenger side under the hush panel. It's pretty simple - unplug the connectors and remove the two bolts. Transfer the old prom to the new. I'd just do a dealer exchange, though rebuilds are available through the discounters, Autozone, Napa, etc.