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-   -   "Coolant Sensor Bad" FINALLY FIXED!!!! (http://www.jeepforum.com/forum/f13/coolant-sensor-bad-finally-fixed-175207/)

phild328 07-08-2005 05:43 PM

"Coolant Sensor Bad" FINALLY FIXED!!!!
 
This is for a 96 Grand - others may be different or not.
Ok, like others I had the annoying "Coolant sensor bad" message on the vic most of the time. And the beeping while you drive - you think a door opened up or something. I've been working on fixing it for what seems like forever. First I didn't know much about the jeep and had no resources. So the coolant level sensor was replaced along with the coolant temp sensor for the PCM.
So the truth is: This message is generated by the coolant level sensor. It is directly wired to the VIC and the VIC is the only thing that uses it. So it really doesn't matter at all. It is just a dumb warning light.
Ok, so how do you fix. I'll bet most of the problems are exactly like mine, but I'll go over the easy stuff first. And Jeep should pay for it because it is a shotty manufacturing flaw. But before I reveal the secret, lets make sure your problem isn't a simple one.
Take the coolant level sensor out and unplug it. First test the sensor. Put an ohm meter accross it and when you push up on the float (as if there is plenty of coolant) it should read 3.3K ohms - or close to, mine is 3.2K. Then let the float drop and you should get closed condition (near 0 ohms).
Now put the ohm meter on the connector from the jeep. First connect it to the black wire terminal. And put the other side of your ohmmeter to a good ground (like the battery term). Should be close to 0 ohm.
Put the sensor back together and plug it in. Give a spray of contact cleaner while you are there. Under the drivers dash, there is a plastic cover near the ODBII connector. Pop it off. There is a orange and white connector that is fairly large, it has 20 wires I believe. Pull it out and find the pink with black stripe wire (same color as at the coolant sensor). Measure resistance between it and a good ground. It should be 3.3Kohm (as long as you have enough coolant in your reserve tank). Spray with contact cleaner and put back together if all is good.
Of course if any of the above is bad, fix the wiring or the sensor. But my guess is it is good. So here comes the fun part.
Tear apart the dash and remove the VIC. Look somewhere else for a dash removal inst. Basically remove the glove box and the panel around it and the panel around the VIC, with two screws behind the ash tray.
Unplug the VIC and take to the bench. Open it up (need torx bit). Get the circuit board out. On the connector - look for your pink with black stripe wire and match to the pin on the circuit board. Then look on the back and look at the solder joint. If you have a magnifying glass or good light - you'll probably see what I saw - a bad solder joint (cracked at the connector pin). Its neighbors may be bad also. Use a soldering iron and reflow with a little new solder. Do the others while you are in there. Put everything back together and enjoy beep-free driving.

Now I get to go rub it into the stealership - since they had no clue what the message even meant. I thought they would know how to fix it - yeah right. If you want it done, you gotta do it yourself.

bx cherokee 07-10-2005 09:31 AM

help !!!
 
will this cause a chain reaction of other sensors malfunctioning as well ??

greasefingers 07-10-2005 10:18 AM

Excellent!! You do indeed learn so much more if there is no one else to turn to, except yourself. My ZJ does not have a VIC so I have no oil level or coolant level sensor. My oil pressure & fuel gauge did go bad, however. I now have fake paper gages glued to my dashboard instead :thumbsup:

user jeep 10-09-2006 12:19 PM

this didnt work for me, you just got lucky!!

phild328 10-17-2006 11:00 AM

If all your connections are good, and your sensor is good, the only thing left is the VIC circuitry itself. You can trace the pcb and wire in a 3.3K resistor in the place of the coolent sensor. Verify the continuity of the traces or get as close to the IC as possible in case some of the other solder joints are bad. Re-flow many solder joints, it shouldn't hurt, should only help. Many electronic failures are due to the solder joint.
Try another VIC if all else fails (though do they have to be programmed to the car, I can't remember?) Only three things to it - the sensor, the wiring in between, and the VIC. Should be an easy fix. The huge thing was figuring out what was connected to what - which is in my first post.
If you didn't replace the sensor - do that first of course. Its like $10. Even if it tests good - it may be different in the car - with the coolent swashing around moving it around it could temporarily go open.

NO1WOLVERINE 10-23-2007 07:59 PM

Correction!
 
Quote:

Originally Posted by phild328
This is for a 96 Grand - others may be different or not.
Ok, like others I had the annoying "Coolant sensor bad" message on the vic most of the time. And the beeping while you drive - you think a door opened up or something. I've been working on fixing it for what seems like forever. First I didn't know much about the jeep and had no resources. So the coolant level sensor was replaced along with the coolant temp sensor for the PCM.
So the truth is: This message is generated by the coolant level sensor. It is directly wired to the VIC and the VIC is the only thing that uses it. So it really doesn't matter at all. It is just a dumb warning light.
Ok, so how do you fix. I'll bet most of the problems are exactly like mine, but I'll go over the easy stuff first. And Jeep should pay for it because it is a shotty manufacturing flaw. But before I reveal the secret, lets make sure your problem isn't a simple one.
Take the coolant level sensor out and unplug it. First test the sensor. Put an ohm meter accross it and when you push up on the float (as if there is plenty of coolant) it should read 3.3K ohms - or close to, mine is 3.2K. Then let the float drop and you should get closed condition (near 0 ohms).
Now put the ohm meter on the connector from the jeep. First connect it to the black wire terminal. And put the other side of your ohmmeter to a good ground (like the battery term). Should be close to 0 ohm.
Put the sensor back together and plug it in. Give a spray of contact cleaner while you are there. Under the drivers dash, there is a plastic cover near the ODBII connector. Pop it off. There is a orange and white connector that is fairly large, it has 20 wires I believe. Pull it out and find the pink with black stripe wire (same color as at the coolant sensor). Measure resistance between it and a good ground. It should be 3.3Kohm (as long as you have enough coolant in your reserve tank). Spray with contact cleaner and put back together if all is good.
Of course if any of the above is bad, fix the wiring or the sensor. But my guess is it is good. So here comes the fun part.
Tear apart the dash and remove the VIC. Look somewhere else for a dash removal inst. Basically remove the glove box and the panel around it and the panel around the VIC, with two screws behind the ash tray.
Unplug the VIC and take to the bench. Open it up (need torx bit). Get the circuit board out. On the connector - look for your pink with black stripe wire and match to the pin on the circuit board. Then look on the back and look at the solder joint. If you have a magnifying glass or good light - you'll probably see what I saw - a bad solder joint (cracked at the connector pin). Its neighbors may be bad also. Use a soldering iron and reflow with a little new solder. Do the others while you are in there. Put everything back together and enjoy beep-free driving.

Now I get to go rub it into the stealership - since they had no clue what the message even meant. I thought they would know how to fix it - yeah right. If you want it done, you gotta do it yourself.

Well Phild328 you are right on many of your findings but I think you made a few typos! :wave: you are incorrect by saying that the sensor in the tank (float) shows 3.3 ohms when it is raised! It will be zero ohms because the contacts are closed. when the float is lowered (coolant low) it wil read the 3.3 ohms. Also when you unpug from the VIC and check that black and pink wire will again read zero ohms with the tank full. So you just had it reversed. But I congradulate you on helping me with my problem!! YES MINE IS NOW FIXED by following philb's instructions!! Thank you very much for this info!

QuadraTokn 10-23-2007 08:03 PM

what the eff? OP has 5 posts and hasnt logged on in a year! well, good info i guess..

nashmd454 10-23-2007 09:18 PM

o well...I don't wanna fix mine if I have to read a post that long....

bill-ns 12-03-2007 12:37 PM

Many thanks to the original poster... this fixed my coolant level sensor prob that I've been having for a couple years now. Found a couple broken solder points.

Bill

ProductUser 12-04-2007 02:21 PM

Nicely done and thanks for posting the solution!

Tony

00MaxSE 03-28-2008 07:47 PM

Wow I have a 96 Grand with the exact same problem! But I don't know if I want to tackle this fix since I'm selling it.

SpeedyCat3 03-28-2008 07:51 PM

It is simple to do.
The most difficult part is to take the plastic bezel out first.

belangers 07-20-2008 04:19 AM

correction again!
 
Quote:

Originally Posted by NO1WOLVERINE (Post 4357608)
Well Phild328 you are right on many of your findings but I think you made a few typos! :wave: you are incorrect by saying that the sensor in the tank (float) shows 3.3 ohms when it is raised! It will be zero ohms because the contacts are closed. when the float is lowered (coolant low) it wil read the 3.3 ohms. Also when you unpug from the VIC and check that black and pink wire will again read zero ohms with the tank full. So you just had it reversed. But I congradulate you on helping me with my problem!! YES MINE IS NOW FIXED by following philb's instructions!! Thank you very much for this info!

Originally Posted by phild328

This is for a 96 Grand - others may be different or not.
Ok, like others I had the annoying "Coolant sensor bad" message on the vic most of the time. And the beeping while you drive - you think a door opened up or something. I've been working on fixing it for what seems like forever. First I didn't know much about the jeep and had no resources. So the coolant level sensor was replaced along with the coolant temp sensor for the PCM.
So the truth is: This message is generated by the coolant level sensor. It is directly wired to the VIC and the VIC is the only thing that uses it. So it really doesn't matter at all. It is just a dumb warning light.
Ok, so how do you fix. I'll bet most of the problems are exactly like mine, but I'll go over the easy stuff first. And Jeep should pay for it because it is a shotty manufacturing flaw. But before I reveal the secret, lets make sure your problem isn't a simple one.
Take the coolant level sensor out and unplug it. First test the sensor. Put an ohm meter accross it and when you push up on the float (as if there is plenty of coolant) it should read 3.3K ohms - or close to, mine is 3.2K. Then let the float drop and you should get closed condition (near 0 ohms).
Now put the ohm meter on the connector from the jeep. First connect it to the black wire terminal. And put the other side of your ohmmeter to a good ground (like the battery term). Should be close to 0 ohm.
Put the sensor back together and plug it in. Give a spray of contact cleaner while you are there. Under the drivers dash, there is a plastic cover near the ODBII connector. Pop it off. There is a orange and white connector that is fairly large, it has 20 wires I believe. Pull it out and find the pink with black stripe wire (same color as at the coolant sensor). Measure resistance between it and a good ground. It should be 3.3Kohm (as long as you have enough coolant in your reserve tank). Spray with contact cleaner and put back together if all is good.
Of course if any of the above is bad, fix the wiring or the sensor. But my guess is it is good. So here comes the fun part.
Tear apart the dash and remove the VIC. Look somewhere else for a dash removal inst. Basically remove the glove box and the panel around it and the panel around the VIC, with two screws behind the ash tray.
Unplug the VIC and take to the bench. Open it up (need torx bit). Get the circuit board out. On the connector - look for your pink with black stripe wire and match to the pin on the circuit board. Then look on the back and look at the solder joint. If you have a magnifying glass or good light - you'll probably see what I saw - a bad solder joint (cracked at the connector pin). Its neighbors may be bad also. Use a soldering iron and reflow with a little new solder. Do the others while you are in there. Put everything back together and enjoy beep-free driving.

Now I get to go rub it into the stealership - since they had no clue what the message even meant. I thought they would know how to fix it - yeah right. If you want it done, you gotta do it yourself.

Well Phild328 you are right on many of your findings but I think you made a few typos! you are incorrect by saying that the sensor in the tank (float) shows 3.3 ohms when it is raised! It will be zero ohms because the contacts are closed. when the float is lowered (coolant low) it wil read the 3.3 ohms. Also when you unpug from the VIC and check that black and pink wire will again read zero ohms with the tank full. So you just had it reversed. But I congradulate you on helping me with my problem!! YES MINE IS NOW FIXED by following philb's instructions!! Thank you very much for this info!

Mine is a 1998 Grand Cherokee, and the float reads 3.3k ohms with the float raised. The circuit opens when it is lowered, it doesnt close. The reading is infinity when float is down....... Another interesting fact is that this sensor is tied to the computer via the VIC, and does force the computer into closed loop, feeding it outrageous amounts of fuel, as it does during warm up. Fixing this increased fuel mileage exceptionally.

Phil was correct!, you must have a Polish float model....lol!

LaCeS OuT 07-20-2008 09:04 AM

Guys the Coolant Level Sensor is in the coolant reservoir. Fix it for $20 and the message goes away. Worked for me.

5.9 ANDY 07-20-2008 03:49 PM

mine is going off now as well, so that is now on the list as well.


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