Hey there,

I've recently bought a "new to me" 1999 Cherokee Classic 4.0L str8 (6) (~157k) and have been having a problem that I would like to run across other owners about.

The check gauges light has been popping up intermittently when I start the truck. To be specific, it doesn't come up every time the car is started and ran. But rather sometimes and others not. I can predict when this will happen because the volt meter hovers at about 12v (1/4) rather than 14v (1/2). Within a minute or two after starting, the meter drops to nothing and the check gauge light appears. This never happens mid drive. Always at the onset.

I have taken out the alternator and tested it. It is fine, the bearings are good and no whining noises. The battery is new within the last year and seems to be holding a charge fine. I've also cleaned the battery connections to the battery.

The car does not show any symptoms of battery issues. It starts fine, the lights and radio work w/o flickering lights, no stalls etc.

This has been going on for about 3-4 weeks. The work around I have figured, is to unplug the alternator from the back plug and put it back. I've tried bulb grease as well with mixed results. I can usually get it to run w/o a problem if I take a moment to turn off the engine and unplug/plug the wire to the alternator and try again (restart).

It's getting cold here, so I have noticed this more often than before. But I am not confident that is exacerbating the problem versus it's just colder and the problem grows more frequent as time goes on.

I suspect a bad ECU?

I've also most noticeably lost gas milage as this "check gauges" light comes on. I was getting ~17-20 mpg or 300-330 per fill. Now the last two tanks have been 230-250 per fill.

I suspect the volt issue on the gauges and the gas are related. Since they happened around the same time. I've also had an intermittent Airbag light. But I have not pursued fixing this as my horn and cruise control still works.

Thoughts?

 

I'll give you a bump because I am curious to hear what some of the more knowledgeable guys have to say.

A lot of threads I have been reading with weird battery problems, one of the first suggestions is to make sure all posts, contacts and grounds are clean.

Curious about the loss of MPG's though.

 

check PCM , it regulates voltage, or could be a bad body ground

wouldnt hurt to check terminals first and clean the posts up for winter, replace terminals if needed, there cheap.

 

The same thing happened to me but mine was once over the summer as I was driving for over an hour. After stopping at my destination and turning her off then back on the gauge went back to 14. Another time it did the same thing but the last time was just this past Sunday. I was on my way upstate at 5 in the morning on a desolate stretch of Rt. 17 when the gauge dropped to 0. I didn't think much of it (major ignorance on my part) until a few minutes later my lights (LED dash upgrade) went dim as well as my headlights. Everyone knows what happened next…she sputtered and shut down. Luckily, I had some friends only a few minutes behind me and we were able to tow it off the highway and eventually swapped out the alternator in a Quick E Mart parking lot (a valuable lesson I learned on this site is always keep tools in your Jeep). I should've had them test it when I returned the core but I was in a rush. She's worked perfectly since but now I have an oil pressure sending unit issue. It never ends, good luck with yours.

 

Grounds! Clean all of them. Take them off and wire brush them. Your symptoms sound like what mine were when my alternator went.

 

I was just having some issues with what I thought was my battery. I couldn't get the truck to start. If I turned the key to the on (but not start) position my radio, gauges etc would come on... slowly and my voltmeter in the dash would read low. Then when I'd try to start the jeep it would kill the power to everything and go dark. I would then open and close the driver door and it would "reset" and I could get the power back to my radio etc again.
It turned out the cause was the negative terminal post and connector to the ground was not on tight enough. I took off the old terminal clamp, cleaned all my negative (ground) wires that connect to it, cleaned the negative battery post and put on a new clamp. Once I tightened it enough everything fired right up just like normal.
When I was trying to figure it out my battery readings were normal and I think that when i was opening and then closing my door it was wiggling the clamp just enough to make the connection work for the lower draw systems (radio and gauges and lights) but not enough for the higher draw of the starting system. I have had this same problem on other vehicles in the past and even though it seems like it might be a long shot I think it's worth double checking, as it's a really cheap fix, it's quick and easy to do and if it is the problem could save you some money.
ALso since you are going in and unplugging/replugging your alternator I would guess that you are also bumping into your battery or moving the wires when you do which may have the same effect as me opening and closing my door. Just a thought. Hope it helps.

 

Clean your grounds. Make sure all connections are secure.

 

It appears after replacing the alternator, she's fine!

I had her tested and passed... whatever. Lesson learned. I ultimately diagnosed her by buying a lcd cigarette volt meter for 5.00 on amazon. She was pushing 12.1, 11.9, 11.8 etc. Then once I would mess with the connection (pigtail) on the alternator or even hit the alternator like a starter, she would go back.

I was getting horrid gas milage at about 230 a tank, now she's back to 330. I've come to learn from experience, loss of gas milage CAN come from a failing alternator.

Tricky buggard to diagnose. I feared the pigtail or worse.

TIP: having the voltage meter handy was nice as it bypassed the computer. It was straight reading the battery. Had the meter on the lighter read 13v consistently, I knew I would have been dealing with a computer issue as the clusters voltage meter reads off the computer FROM the regulator in the alternator. Nice 5.00 investment saved a lot of headache.