Questions and Answers

Jeep Cherokee Power Problem? Q. Vincent, I have a 1997 Jeep Cherokee Sport, inline 6 cylinder, automatic transmission, A/C, and it currently has 63,000 miles on it. We bought the Jeep used about one year ago. It drove like a dream when we test drove it and for about the first two months we owned it. That's when our problem first started and continues to today. Originally, the Jeep would do one of three things.

1) When starting the vehicle, the instrumentation cluster, would not come on. I mean all the gauges were in their off position. When this happened, the automatic transmission would act like a manual transmission. It was jerky starting out, and I would have to put it in neutral, when coming to a stop or it would stall. If I would shut it off and leave it off for a couple of minutes and then turn it back on, the cluster would come back on and everything would work normally.

2) When driving, the check engine light would come on, and the transmission would appear to go into neutral. You would be driving along and all of a sudden, the tachometer would show the RPM's spike, there would be no speed increase and the engine would scream. The only thing I could do was pull over, shutoff the engine, restart and everything would be happy again.

3) When driving, the check engine light would come on and the transmission would shift oddly (not the neutral situation in the previous note). I am assuming that is when it went into "limp in" mode. It was drivable, not real smooth.

Points to keep in mind:
1) When driving, the instrumentation cluster would never die, that would only happen when starting the vehicle (no difference to the engine being hot or cold).
2) When the vehicle would give me the situation of being in neutral, I could always get it driving again by shutting the vehicle off and on again. It may drive fine for 5 feet or 50 miles, but it would always start out driving normally.
3) When the vehicle would appear to be in a "limp in" mode, it would be fine the next time I would drive it.

I took the vehicle to a Chrysler dealership in our area, to have it looked at. They hooked it up to their computer and ran their diagnostic tests. The mechanic admitted he didn't know what the cause of these issues was because the testing would get so far and then it would fail out to a default state.

This wasn't leading them anywhere. He told me to bring it back, when it was acting up again, and they would retest it (free of charge, thank goodness).

I did that very thing on two occasions after that. The results were the same. The best guess they could give me was a problem with the TCM (Transmission Control Module), but he would not replace it because it is pricey and he wasn't sure it was the culprit.

I then gave it to a friend of mine, who is a certified Chrysler mechanic, who works at a different dealership. He was running into the same situation. I let him drive it and work on it for about two months, in total. He saw a service bulletin on the instrumentation cluster. He had to fix a faulty connector on the back of it.

As of now, I cannot remember a time that the cluster has failed on start-up, but I am still experiencing the other two issues. He tested the wiring and connectors and couldn't find anything wrong. We then decided to change out the TCM. I found a salvage yard in North Carolina that had what I needed. He changed out the TCM.

It drove like a dream for about a week and then the same things started. We then decided to change out the PCM (Powertrain Control Module). I got one from a different salvage yard in North Carolina. I installed it. The Jeep drove fine for about a week and the same things started again.

As of now, I am getting MIL codes 12, 45, 66 or 12, 66, 45. Each time I get a failure (check engine light), I check the MIL codes and it is one of those two combinations. At this time, I don't have any of the P-codes with me. I can get them for you, if you need them.

I was doing some reading on your web-site and found an article where there was a Dodge Intrepid (I believe it was), that was getting a 12, 43, 66. The only difference being they were getting a 43 and I'm getting a 45. In that article, you recommended changing out the ASD relay (Auto Shut Down). I switched the relay in the Starter slot for the one in the ASD slot to see if this would show any difference. Yet again, I drove it for a week with no problems and it started acting up again.

This morning on my way in to work, it did that neutral thing; the only difference is that it started working on its own. I didn't have to pull over, shut if off and back on, it recovered on its own and drove fine. I almost believe that it is a power failure of sorts, because my MIL codes always show a 12 at the start of the list, even at the beginning of all this, the 12 was the first code set. With this in mind, I remade all the grounds I could identify.

As of today, I am no better off than I was before. I really need some advice on what to do next. Thank you for your time. If you need any other details, please e-mail me back.

Neil

A. I think the code 12 is significant here. Code 12 is "Battery input to PCM disconnected during last 50 key starts." So, if you are not disconnecting the battery, then something else is causing an interruption of power to the PCM. This is what we have to look at now. Right now I think you're looking at a bad connection or interrupted circuit.

I don't have any correlations for code 45 or 66. P codes would be helpful here.

I assume you have tested all the fuses with a test light or ohmmeter.