Help, My Grand went crazy!

[r6cyclegal]

Yesterday morning while on I-79 my 2000 Grand Laredo went crazy. The ABS & BRAKE light came on, the odometer started blinking and the speedometer started shooting from 40-70 real fast. The brakes worked fine and it was running fine. The time on the radio got reset to 12. I finally was able to stop and shut off the engine and restart it. It was fine for the 4 miles to work.

My mother has my car today so I figured I had to get it checked even if it was a glitch. I called my mechanic and he said it sounded like the alternator. Being as cheap as I am, I took it to Advanced Auto to have them check the battery and alternator. They were fine so I took it to the mechanic. They said the negative battery terminal was loose. There were no codes.

It was fine driving it to the mechanic and home. I haven't heard from my mother yet so I'm guessing it's fine today. Has this happened to anyone before? Is that what the problem sounded like or did they make that up so they didn't have to say they found nothing? The girl at work said their truck did the same thing and it was the computer board???

Bill, I already know your opinion so you can skip this thread :wink:

[jdetar]

typical electrical gremlins. i'd say it's not your comuter though because of what was being effected. it seems to be a more general power problem such as the battery.

[r6cyclegal]

typical electrical gremlins. i'd say it's not your comuter though because of what was being effected. it seems to be a more general power problem such as the battery.

That's what I thought so I checked the battery terminals and fuses when I got to work. I just saw if they were very loose. I didn't really try to turn them so they may have been loose. :smt102

[OverkillZJ]

Typical ZJ/WJ electrical problems. I agree with the others on this, sounds like some power loss / spike that caused the ECU to reset while driving. Glad you got the alternator checked, I was thinking maybe it was spiking (voltage regulator is integrated on our alternators)

If the negative on the battery was really lose and not making a good connection, I guess it's entirely possible that your electrical system was running only off of the alternator which is not smooth power by any means. The battery kind of evens out the power absorbing peaks and providing during drops.

Just food for thought. I'd keep an eye on your connections, fuses and just keep an eye on things. I don't think you have a cooked ECU or anything though.

[Mel85CJ]

I've had some similar electrical gremlin on my '01 WJ.. except it just consists of that every now & again everything just *resets*.. like the clock, radio etc.. it will happen when I'm driving..

d/c is absolutely the WORST when it comes to electrical gremlins IMO.. my 300M I had before the WJ was even worse...

-Mel

[Sarge33]

My 1998 went ape s**t and it was a fuse under the hood! Never threw any codes, just reset everything. I had corrision in the fuse panel under hood from driving through the high waters in Carneige. Simple fix, but took awhile to figure out what it was! 8)

[OverkillZJ]

d/c is absolutely the WORST when it comes to electrical gremlins IMO.. my 300M I had before the WJ was even worse...

-Mel


That's not just your opinion, I think it's just an industry accepted fact, LOL

[r6cyclegal]

I only have 32,000 miles on it so I hope it's not going to continue!

I opened the fuse panel thinking I would check the fuses and then saw there were like 30 fuses!!!! 8O Forget that! I made sure they were all secure but didn't even take the time to read them to see which one does the instrament panel. (lazy I am)

Thanks to all for the guesses!!!

[r6cyclegal]

Dave, How accurate is the alternator test that Advanced does?
Matt, if you say the alternator might be peaking, could it fool the test at Advanced?

I'll let you know if it happens again but didn't know if this is something that is expected.

Thanks for all the replies!! :wink:

[Bill]

Hmmmm.... these reasons all sounds very familiar... :wink:

[OverkillZJ]

I thinkn Advance load tests it? Any test can be tricked. This is all totally speculation so for all I know it was a sun spot that caused it ;)

[dp]

You can't 'trick' the alternator tester at advance auto. Even if you alternator was bad, you'd either be running right off the battery (at least for a little while -- which your car should be able to do just fine for a minimul amount of time anyway) or you'd be blowing out your headlights and stuff from too much voltage.

Sounds like you just hit a bump and lost ground for a split second -- enough to cause the computer to have to start everything over again. No big deal, it happens. If it happens again, I'd say you need to do some further investigation.

It's also possible that a fuse could have blown and blown in a manner that it just welded itself back to itself -- I've seen it happen. But then there'd be a reason for the fuse to blow again, and in all likelihood, it would blow again.

Honestly, I wouldn't worry about it unless it happens again.

[OverkillZJ]

I wouldn't worry about it either. But just for arguments sake (with dave)

You're telling me that the alternator test at Advance is 100% accurate? You're telling me that a condition can't exist where it tests fine but has an ocassional issue that isn't always detectable? No test for anything is perfect, in any scenario.

Trick was the wrong word.

[Wrecker]

A bad connection at battery can cause all kinds of things. Once had a deisel in old dodge dealer I worked at. One of best techs could not figure a driveablity cond. Tried all sorts of things. Call tech line and they said clean terminals. Tech said if that was all it was he would quite. He ate his words. Dirty neg termonal. Always need a good bucket of dirt.

[dp]

I wouldn't worry about it either. But just for arguments sake (with dave)

You're telling me that the alternator test at Advance is 100% accurate? You're telling me that a condition can't exist where it tests fine but has an ocassional issue that isn't always detectable? No test for anything is perfect, in any scenario.

Trick was the wrong word.

uhm...it's not whether or not an 'alternator test' is 100% accurate or not. It's a voltmeter -- so yes, I would assume, that in a perfect world, where the machine is functioning as it should be, it will always display and record the voltage that is actually present. Machines fail, Matt..don't be dense. As far as the ammeter being accurate, I guess the same would hold true.

No doubt there's a time the sensors will display a wrong reading...but the machine doing the testing saying Advance Auto Parts on the side has absolutely nothing to do with whether or not it will work properly.

[OverkillZJ]

Point in fact is if it's simply a voltmeter, they're only testing the thing in one given situation, while the vehicle is at rest (and odds are only at idle or maybe rev'd up a lil') - there is room for error.

[Bill]

Damn... I knew when she posted this thread that you two would be doing this AGAIN!

I just knew it.

[DMG]

I have seen an alternator with an intermittent fault in the voltage regulator or diode trio that would test ok if you caught it when it was working. That would(and did) fool the test.

However, I think the loose battery cable was probably the cause.

My$.02 David

[dp]

Point in fact is if it's simply a voltmeter, they're only testing the thing in one given situation, while the vehicle is at rest (and odds are only at idle or maybe rev'd up a lil') - there is room for error.

I'm not arguing here, Bill...Matt is just dense.

[OverkillZJ]

Point in fact is if it's simply a voltmeter, they're only testing the thing in one given situation, while the vehicle is at rest (and odds are only at idle or maybe rev'd up a lil') - there is room for error.

I'm not arguing here

Must be a first.

You implied that when Advance tests an alternator and say's it's ok, it's fine and there's no way their test could possibly be wrong. That's bull, so I decided to start an argument for you for once considering you seem to like doing it with me in every other damn thread on the board. Density has nothing to do with it.

[r6cyclegal]

Almost 2000 miles since my problem and no trouble so hopefully it was just the battery terminal. :D

Thanks for all your input!!