TJ: Engine Shuts Down

[Mike]

I need some help on this one...

I was driving the Jeep home from work today and the engine stopped. All of the gauges dropped to the off position. The motor was still turning but only due to the fact that the gears were engaged and the Jeep was rolling.

After pulling to the shoulder, I restarted the engine and checked under the hood but found no obvious problems. I drove another mile or two and it did it again. This time I checked the OBD and found no codes.

I restarted the engine and drove about a mile and it died again. This time when I checked the OBD, it came back with "NO LINK". The engine would turn over but not start. After 5 minutes or so, the OBD read "0 CODES" and the engine cranked again.

This happened one more time while I was trying to get to an exit. Once off the road, I tested it one more time with the same "NO LINK" result happening. It took a much longer time (10 minutes or so) before the Jeep would crank again.

I got my truck and flat-towed it home. It cranked when I hooked it up and it cranked again when I unhooked it and put it in the garage. No OBD codes were ever thrown.

Any idea what could be causing this?

[aw12345]

Loss of power to the ecm will do that since most all of the instrument cluster runs of a data link that's pretty much driven by data from the ecm. I would start looking at power and ground for the ecm and go from there

[evldog]

I concur. It sounds like an ECM issue. Pull the connections and clean them with some electronics cleaner/lubricant and test drive. If one of the connections is loose or dirty, it could interrupt the signal to your ignition system and kill the motor. Hope it is just one of the plugs, because if it is the ECM itself, they are very pricey. Good luck and let us know what you find out, just in case.

[RAT]

I agree with the other guys. Check all of the power connections.

[HB Jeeper]

Definite ECM problem.

[Mtbikbob]

It does not sound like the CPS. But I wonder. Any thoughts that it might be? Its a cronic jeep problem.
BobO

[Jason]

Do you have a kill switch? Mike, I chased everything under the sun and my problem turned out to be a kill switch I thought was disconnected but was only bi-passed. Check any after market light connections and such. Jeeps rattle a lot on trail and something may have come loose.
My 2 cents.

[Mike]

Thanks guys. I'm afraid that it might be the ECM too (The Diagnostics book calls it a PCM). I will do the checks as suggested. Is there anybody out there with a DRBIII that could borrow? Some of the tests require this reader.

[aw12345]

Thanks guys. I'm afraid that it might be the ECM too (The Diagnostics book calls it a PCM). I will do the checks as suggested. Is there anybody out there with a DRBIII that could borrow? Some of the tests require this reader.

Start with some simple tests, number one 12 volts supply to pcm, secondly good ground to pcm. Third ignition power to pcm
Then when it doesn't want to run can you set codes by disconnecting sensors?. When it doesn't want to run is the check engine light on, when you try to crank it? Also do you have a means to get data stream out of the pcm with a OBD2 scanner or something likewise?

[Mike]

Looks like I can do pretty much all of the tests with tools I have according to the Diagnostics book.

Then when it doesn't want to run can you set codes by disconnecting sensors?.

I will have to test it.

When it doesn't want to run is the check engine light on, when you try to crank it?

All of the dash lights come on when I try to crank it. It seems to go through it's normal light routine, but the fuel and other gauges sit still.

Also do you have a means to get data stream out of the pcm with a OBD2 scanner or something likewise?

Yep. I have an OBDII. That's how I know that it has a "No Link" message when the problem happens.

I'll test a few things on Sunday and let you know what I find.

[aw12345]

One of the first things to do is disconnect a few sensors to see if the ecm creates codes, if it does then it has power and ground and you can pretty much rule that part out

[peteyg]

Not a TJ, but I just recently got done dealing with Sudden Death Syndrome on my '96 XJ (OBDII, same PCM and connections as TJ's). I went through all the same stuff you are, and wound up replacing just about everything. I ran across this post: http://forums.cnet.com/7723-7811_102...fixed/#2490641 and thought, "Hey! That sounds like MY problem!" So I removed the case screws, and haven't had a problem since. I was JUST about ready to junk the Jeep....

Edit: One side benefit to doing all that work: I just smogged the Jeep today, and it runs CLEAN....SUPER clean (0 PPM NOx on the Dyno). Of course, I replaced everything.....and I mean everything, including the CAT.

[GP4Play]

Not a TJ, but I just recently got done dealing with Sudden Death Syndrome on my '96 XJ (OBDII, same PCM and connections as TJ's). I went through all the same stuff you are, and wound up replacing just about everything. I ran across this post: http://forums.cnet.com/7723-7811_102...fixed/#2490641 and thought, "Hey! That sounds like MY problem!" So I removed the case screws, and haven't had a problem since. I was JUST about ready to junk the Jeep....

Edit: One side benefit to doing all that work: I just smogged the Jeep today, and it runs CLEAN....SUPER clean (0 PPM NOx on the Dyno). Of course, I replaced everything.....and I mean everything, including the CAT.

Cool info, thanks Pete

[brokenujoint]

As an aircraft mechanic i should of known about the ol screw routine... Dang that screw. It's grounded more than one airplane here at Delta...

[6spdYJ]

Also check your fusible link for any crunchyness - indicating a corroded section inside the insulation.