CCKen, how is your MI XJ so rustless???

PCM/ECU connectors:

 

Update: I checked all the grounds from the PCM to their respective components, checked various other grounds and created a new main ground from chassis to battery which should be more than sufficient. The battery temp. sensor has some wires exposed so I coated them with liquid tape, considering getting a new one.

I am still have the same issues, here are a few videos of what my gauges are doing. Sometimes everything is normal (excluding fuel and speed) and other times they jump around.




I am thinking it almost has to be the PCM, I can't think of what else I could check.

 

Lipstick powder and paint makes a lady what she ain't.

 

Here is a deal Cruiser wrote for 90 and earlier Jeeps, just in case ?

Improving the Instrument Panel Ground
The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼" or 5/16" head on it.
This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.
The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.
Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.
Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.
**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
　
Revised 11-29-2011

 

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I don't know WTF is happening with the reply function. It kept duplicating the ONE image I tried to post and I couldn't edit it out.

Maybe a Mod could delete the entire post and I'll start over.

 

Here's what I tried to say in the first reply that went nuts:

After viewing the videos this looks to me as though it could be a CCD Data Bus wiring problem between the PCM and the Instrument Cluster. I didn't see where an Instrument Cluster Actuator Test was performed. Try this test and see how all the instruments respond.

Instrument Cluster Actuator Test

(1) Begin the test with the ignition switch in the Off position.

(2) Depress the trip odometer reset button.

(3) While holding the trip odometer reset button depressed, turn the ignition switch to the On position, but do not start the engine.

(4) Release the trip odometer reset button.

(5) The gauges should cycle through their ranges, stopping at intermediate readings, going up and going down, at two second intervals, as shown in the chart in Figure 2. The indicator lamps should cycle on and off.

(6) The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test, if the ignition switch is turned to the Off position during the test, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM on the CCD data bus during the test.

 

I will test the cluster but I cant imagine that the gauges would affect the voltage at the battery leaving me to think it's still the PCM

 

If the PCM is defective it will show up on the actuator test.

I could see if it were strictly a voltage regulation problem that the voltmeter in the instrument cluster would be acting up, but when all other instruments are cycling from min to max, like in the videos, something else is wrong as well.

Let us know what the instruments do during the actuator test.

 

Does you instruments act like that in the videos when you first start your Jeep and you sit still at idle? The videos only show activity when you are driving.

Have you examined the B+ lead from the alternator at the PDC for corrosion and security of attachment (see pic). It's the connector under the small cover at the end of the PDC with the green cable (fusible link).

 

I did the gauge cluster test and everything was fine, I bought another PCM today and my speedo and fuel are working again but I am still having the voltage problem. It's fine until the Jeep warms up I noticed than things started to go all strange generally when I'm coasting or not giving it a lot of gas but if I give it some juice going uphill it goes back to normal.

I did not check the B+ from the alt. yet but I will tomorrow and let you know how that goes.

I also noticed the upper O2 sensor wires are completely torn off, I purchased a new one but it's completely stripped out and impossible to get off currently so I will take the exhaust off and put it in a vice and heat it to remove it. Could the o2 sensor circuitry possibly be part of the issue?

 

Now that I think it about it, the engine runs off of the ECU mixture while it's warming up and once it's warm it runs off the o2 sensors and that's around the time when I have issue. It's a possibility and I need it anyways...

 

"The battery temp. sensor has some wires exposed so I coated them with liquid tape, considering getting a new one."

"I also noticed the upper O2 sensor wires are completely torn off"

Any idea what is going on with the wiring? Is this a barn Jeep where Mickey had his way with it for 2 or 3 years?

 

the o2 sensor was torn from offroading i believe and the battery temp sensor wires seem to be pressed on by the battery base plate. I'm going to get a new battery temp sensor and raise the battery up off the wires as well as replace the o2 sensor. I checked the grounds with a multimeter and they all seemed fine.

If it was a ground issue I would assume I would have the voltage issue as soon as the Jeep starts up but if it's a sensor issue it would be once the engine warms up and begins to read the sensors. Correct me if i'm wrong though.

 

87-90>ECM 91 on PCM, I think you are correct in principal. (yea, you have a Power-train Control Module, not an ECU, "semantics")

There might be other sensors besides the 02 that come into play as well...can't say which

The cps might screw up warm as well.