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-   -   Gauge Cluster Problem 1996 GC v8 limited (http://www.jeepforum.com/forum/f13/gauge-cluster-problem-1996-gc-v8-limited-1422788/)

BurlaT3 09-30-2012 08:47 PM

Gauge Cluster Problem 1996 GC v8 limited
 
Replaced an alternator after having alot of problems on computer controlled systems. The new alternator started putting out 19v on voltmeter, so I rolled around the corner into my driveway and killed it. They tested the alternator and assured me that it was within the range of 'good' and told me that my computer was not regulating as it should as the most likely problem. I had been having problems as I said for a long time, so I replaced the pcm. The battery was ruined with the overcharging so it was replaced with new. New battery, new alternator, new pcm, another new pcm. Here is what it does.

Starts and runs good, voltmeter and all other gauges look good, then after about 30 to 40 seconds, all guages, tach, speedo, every gauge goes to rest position. After another 20 seconds or so the ABS light comes on then about 10 more seconds lights up the check gauges. Have let it run on for several minutes, but does not come back. If I kill it and restart it immediately, same results as above.

Have read all threads that I could find that seem to remotely relate, and have checked all things that seemed could relate. Have cleaned up all the relays and fuses in the distribution center. Have checked all the grounds. All seem good. The schematics posted in my hayes book show that the cluster is controled and monitored by the pcm so the bcm is not an issue.

I am looking for suggestions of anything that could help. The display on the inside (vehicle info center?) has burned out years ago. Could this be related? If so why no problem till now?

ZeeJay1997 10-02-2012 06:01 PM

The instruments are controlled by the PCM over the CCD bus. After two PCMs and consistent, repeatable symptoms at boot up, my best guess is that the cluster is bad.

KoreaZJ 10-02-2012 09:58 PM

Welcome to JF!

When everything quits... do the turn signal indicators and cluster illumination lamps still work?

BurlaT3 10-04-2012 09:17 PM

I will look into the CCD Bus but I am having a hard time understanding how if it is not the input from the pcm quitting then how it can be anything but a bad ground. All the gauges should be receiving different electrical levels to be displaying what look like normal readings. It seems to me that if they all quit at the same time it would have to be grounding, computer, or one heck of a simultaneous short on at least a half a dozen different wires. And the repeatability seems to also point away from the short scenario. Could it be a protection built into the pcm? Does anyone know if the pcm or any other component moniter the altenator separately from the readout on the voltmeter? The shutdown seems too reactionary to be random, like it is a response to something like too much power, for instance. The voltmeter is reading just a little bit more than it used to but I assumed it was just working to recharge after starting. It is nowhere close to the 19 reading that I was getting after putting in the new alternator.

Thanks for the input I will look into the turn signals, indicators, and dash lights in the area. Those are some good thoughts also. I wont be able to check it out till the week end. Will post when I know more. (in between hair-pulling and occasional bouts of depression)

ZeeJay1997 10-04-2012 10:45 PM

The cluster is an electronic module within itself. It is susceptible to failure of solder joints and other components.

The voltmeter is on the CCD bus, You can tape a meter on the dash and run leads to alternator.

ratmonkey 10-05-2012 11:17 AM

The data is routed through the bcm. Any other interior functions not working correctly?

BurlaT3 11-25-2012 03:28 PM

Here is an update. Still not fixed. Computer Remanufacturer (Cardone) says that the most common problem is the Crank sensor returning an out of range signal that is causing that portion of the pcm to shut down preventatively. This has lead to a surprising discovery.

In order to test this sensor the harness connector needs to be tested then backprobed when turning to test the hall effect. The three wires are supposed to be as follows. When the key is on motor not running, center wire is ground with no resistance to ground at battery, 1 outside wire should test at 5+v and one at 0v. When turning over, 0v wire should spike at same volts as other outside wire so would probably show as 2.5v on an averaging meter.

Here is what I have. With the sensor unpluged ground in connector tests good. Both outside wires in the unpluged connector test at 5.2v. With the key on or off.

I opened up the wire enclosure and the two wires that should have power are mated with the ground wire with the ground inbetween like a flat cable, so a short between the two outside wires without direct shorting into the ground lead seems unlikely. But what seems more unlikely is that the wire that supplies this sensor, the cam sensor, manifold pressure, coolant temp , and otheres with the supply voltage (5.2 v) would be hot with the key in the off position. Just for the record, there is not a parasitic
drain.

I know what I think. Please give me your ideas. Thanks

dusterdude 11-25-2012 03:47 PM

Im curious as hell about this

G-Man2 11-25-2012 07:24 PM

Quote:

Originally Posted by BurlaT3 (Post 14505727)
Here is an update. Still not fixed. Computer Remanufacturer (Cardone) says that the most common problem is the Crank sensor returning an out of range signal that is causing that portion of the pcm to shut down preventatively. This has lead to a surprising discovery.

In order to test this sensor the harness connector needs to be tested then backprobed when turning to test the hall effect. The three wires are supposed to be as follows. When the key is on motor not running, center wire is ground with no resistance to ground at battery, 1 outside wire should test at 5+v and one at 0v. When turning over, 0v wire should spike at same volts as other outside wire so would probably show as 2.5v on an averaging meter.

Here is what I have. With the sensor unpluged ground in connector tests good. Both outside wires in the unpluged connector test at 5.2v. With the key on or off.

I opened up the wire enclosure and the two wires that should have power are mated with the ground wire with the ground inbetween like a flat cable, so a short between the two outside wires without direct shorting into the ground lead seems unlikely. But what seems more unlikely is that the wire that supplies this sensor, the cam sensor, manifold pressure, coolant temp , and otheres with the supply voltage (5.2 v) would be hot with the key in the off position. Just for the record, there is not a parasitic
drain.

I know what I think. Please give me your ideas. Thanks

Without a detailed schematic it's hard to say but my guess is the unplugged test may not be valid. Without the load of the sensor the signal line may be floating high from the computer. What does seem like an issue is having 5 volts with key off. Just for grins you might check all fuses. I know some blown fuses can cause very weird symptoms. If you find one blown, then there is another problem to fix.

ZeeJay1997 11-25-2012 08:56 PM

Will it crank and run? If the crank sensor is shorted like you are saying, it would not run.

What happens if you unplug the crank sensor and check voltage on the harness from pin 1 to pin 2 with switch on and switch off?

While it is disconnected check the sensor side for resistance between middle and right pins (B&C). Any resistance at all is a bad sensor.

When you back pin 3 with harness connected, it may have 5 v on it if the flywheel notch is aligned with the sensor.

BurlaT3 11-26-2012 07:02 AM

no blown fuses, Gman2, and the harness wiring is tested with the connector undone then the part is tested while connected thru back probing, according to the manual I have. I am sure there is more than one way to do it but I have no confidence in any plugged in test when the harness connector doesnt test out like the book says it should.

ZeeJay1997 It runs great. Check first post, problem is not that it wont run, the gauge cluster shuts down after short time. I dont believe it is shorted that is just one posible explanation of the wiring harness test. I dont even think it is likely. The connector harness side was checked the way you said. Pin 1 to 2 and 2 to 3 key on and key off the same 5.2v bumped the flywheel twice retesting on and off each time, and I am sure I didn't line up on notch all those times.

I did not check the sensor side. My book gives the steps to determine which wire returns the hall effect then test that wire. Mine are not labeled abc and both outside wires on harness are testing the same so no way to tell them apart. I actually dont think the sensor is likely to be bad since the harness is testing so wrong to startwith. This whole rabbit trail is the computer remanufacturer's idea. I did not test for resistance on the sensor side with unpluged because my manual didn't suggest that. It sounds like a good idea but since i dont know how it is supposed to read, I haven't. Is A to B supposed to test with no resistance as well?

Thanks for your input, and please keep thinking it out with me. I have my ideas but dont want to guide you guys down my thoughtpath. When this is done I will follow up with the answer that made it work so the brain teaser will have an answer. Keep following the thread and post any ideas and maybe we can turn my yard ornamant into a commuter.

ZeeJay1997 11-26-2012 07:35 AM

Turn switch off.
Put leads across 1 and 2 on crank sensor body side harness.
One at a time, disconnect MAP, cam, and TPS.
If any of these make the voltage go away, more diagnoses is needed.
Now everything is out of the circuit but harness and PCM.
If you still have 5 volts, pull PCM fuse and disconnect black connector on PCM.
Check all three crank sensor wires to frame of vehicle and to each other.
If you get no continuity to vehicle or between wires, PCM is more suspect but i wouldnt call it bad just yet.

I have no idea why this would make the instrument cluster crap out...

96zedjay 11-26-2012 08:03 AM

Does the CCD Bus Bias voltage change when the Instrument cluster drops out?

BurlaT3 11-26-2012 09:29 PM

Thanks for the tip. I wont be able to get to this now till Friday but all of the sensors that you said and a few others have either one or two pins in common to the pcm, so all of them will get pulled twice because 1 or 3 is supposed to have voltage when the key is on and the other isnt. Since they both have same voltage no guess which is which.

"If you still have 5 volts, pull PCM fuse and disconnect black connector on PCM."

Where would I find the PCM fuse and I think the three connectors for the PCM are all three black, but not sure. Would the PCM fuse be in the power distribution center? My original vehicle owners manuals that are still in the Jeep folder shows a different power distribution than mine in the vehicle and the lid doesnt say what most are for. My Haynes manual doesnt even show the same one. I have checked all the breakers by testing the pins on the back based on the specs that the haynes says they should test at and none seem to be a problem. I figured if I ever needed to know badly enough I would just have to snoop it out one lead at a time.

Thanks for your tips.

BurlaT3 11-26-2012 09:39 PM

96zedjay, I am not even sure where the CCD Bus is. I am able to find most of what I need or at least fake it with my Haynes manual, but you got me there. You and one other poster on this thread have mentioned this but I can find no mention of it in my book. I have wiring schematics for mine and while they might not be complete, I have not found anything missing so far but this CCD Bus. Could this be called by another name?


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