still need help with temp gauge...

[jwendell]

i have a '96 JGC laredo, 5.2 V8, my temp. gauge reads the maximum all the time even though my engine isn't overheating, this causes my "check gauges" light to appear. this also causes my interior lights to blink noticeably when driving at night. i no longer have delay on my windsheild wipers. one time when i was driving the alarm starting going off, but that only happpend once. i have replaced the coolant/temp. sensor and that didn't fix the problem. after i replaced the c/t sensor, the "check engine" light appears but shuts off after a few miles.

i've already tried turning my key on/off three time and leaving it on "on" on the 4th attempt to have my computer let me know what's wrong, but that didn't work???

also, my computer doesn't tell me that anything is wrong, i read in a thread that the computer should tell me a sensor is bad.

is my computer going to hell??

does anyone have any idea to what may cause my guage to read faulty temps?

thanks for the advice!!

jw

later that day....
i hooked up an OBD II to it and it read P0118 "Engine Coolant Temperature (ECT) Sensor Circuit High Voltage". is this simply telling me what my gauge is telling me?
any ideas on how to fix this error???

thanks...

PROBLEM SOLVED

after some time and convincing the dealer to actually try even though they said it wasn't the problem. the body control module (BCM) fixed this problem. don't let the dealers try and tell you it is something else, they tested my BCM and said it was fine. i really had to persuade them to try a different BCM. this is something you can actually replace yourself, the BCM was under the steering wheel on my '96. thank you to everyone who participated in this discussion.

jw

[89ltd]

how do you know the engine is not overheating? Does the temp gauge go to the top as soon as you start the jeep?

[larrydm]

Hi
I have the exact same problem on my 1997 JGC 4.0 6 cyl and as yet have not figured it out. I was hoping for some advice. My dome lights and wipers are doing the same as yours. My local Chrysler dealer put my jeep on the computer and told me it was my instrument cluster. I replaced it but the temp guage still goes to max temp as soon as you start the engine. I checked for PCM codes and got the same message as you- code 22 which indicates an over or under voltage from the temp sensor. I Ohmed out the sensor and it is well within the specs when cold and at running temp of approx. 210 deg. I am getting 5.14 volts supplied to the temp sensor. Specs call for approx. 5 volts. Is the .14 enough to give the error? At this point, I'm stuck and could sure use some help as to what to try next. I considered the power train control module but all my other controls seem to be working well.

Thanks

[jwendell]

Originally Posted by 89ltd

how do you know the engine is not overheating? Does the temp gauge go to the top as soon as you start the jeep?

yes, it goes to the top immediately after i start my jeep. it even goes to the top when i turn my key on the 'on' position when it isn't started.

[jwendell]

Originally Posted by larrydm

Hi
I have the exact same problem on my 1997 JGC 4.0 6 cyl and as yet have not figured it out. I was hoping for some advice. My dome lights and wipers are doing the same as yours. My local Chrysler dealer put my jeep on the computer and told me it was my instrument cluster. I replaced it but the temp guage still goes to max temp as soon as you start the engine. I checked for PCM codes and got the same message as you- code 22 which indicates an over or under voltage from the temp sensor. I Ohmed out the sensor and it is well within the specs when cold and at running temp of approx. 210 deg. I am getting 5.14 volts supplied to the temp sensor. Specs call for approx. 5 volts. Is the .14 enough to give the error? At this point, I'm stuck and could sure use some help as to what to try next. I considered the power train control module but all my other controls seem to be working well.

Thanks

well i've tried fixing this problem on my own, replacing the sensor, checking voltage and resistance, and i even replaced the thermostat (which was broken when i took it out). i thought for sure that that was the problem, but the temp gauge still maxes out. time to bring it to the dealer. do you remember how much the instument cluster cost??
I really don't think that a .14 voltage would cause your temp gauge to max out, like you said, specs say aprox. 5 volts. if you have any other ideas please share them. thank you.

[larrydm]

Originally Posted by jwendell

well i've tried fixing this problem on my own, replacing the sensor, checking voltage and resistance, and i even replaced the thermostat (which was broken when i took it out). i thought for sure that that was the problem, but the temp gauge still maxes out. time to bring it to the dealer. do you remember how much the instument cluster cost??
I really don't think that a .14 voltage would cause your temp gauge to max out, like you said, specs say aprox. 5 volts. if you have any other ideas please share them. thank you.

I paid 50.00 from a salvage yard so I suppose it's possible that they could have given me one with the exact same defect but I doubt it since my Chryslwer dealer said that they have never seen an instrument cluster have a bad temp guage. Me dealer quoted me 180.00 for a brand new one and you have to purchase it through a dealer. I may go back to the salvage yard and get a different cluster and try that just in case.

Thanks

[glass]

just a guess... but could there be a short in the wires going to the temp gauge ??

[JDPascal]

Hi jwendell and larrydm

The instrument clusters on these models are a computer by themselves and operate by talking to the powertrain control module thru something called the CCD BUS. The cause of your problem could be with anything that uses the CCD bus system. Connectors that have extra resistance, aftermarket installs that have been crossed with CCD wiring or just bad connections in that circuit or a bad PCM with old programming and circuitry.

Your sensors, computers and instrument cluster could be fine but still have a temp gauge problem or a whole instrument cluster showing no or bad readings.

Check with the dealer to find out if there is a newer version of your PCM available. There is a number on the PCM to identify it and sometimes a sticker on the hood to show if it has been changed and when. I know that mine was updated before I purchaced the vehicle.

Hope I explained this right. I'm only useing words and explaning it how I understand it (which isn't very deep).

What you are likely looking for is a technician with a good electronics background to trouble shoot it.

Sorry if this is not an encouragement to you.

JD

[jwendell]

Originally Posted by glass

just a guess... but could there be a short in the wires going to the temp gauge ??

there could be i guess. i checked the voltage coming out of the temp/coolant sensor and it was between 4-5, i know 5 is average but if it is lower it wouldn't cause the gauge to max out. if there was a short, would there be an voltage? or how else would you detect a short? i am going to replace the sending unit today. i'll post back later with the outcome. thanks for all the replies...

[xj31]

I have seen this before and it was actually the body computer.I still have no idea how because according to schematics,it is not supposed to have anything to do with the temp gauge.I had the luxury of an identical jeep to swap test parts from.The bcm was just a guess after trying the sensor,gauge and pcm.

[smichael]

try disconnecting the connector to the thermostat and start the car-see what the gauge reads

[jwendell]

Originally Posted by smichael

try disconnecting the connector to the thermostat and start the car-see what the gauge reads

do you mean disconnect the connector to the temp. sensor?? i've tried disconnecting from the sensor and still reads high. I was also told that if i turn the key on without starting and the gauge reads high, the thermostat has nothing to do with it...thanks

[smichael]

try disconnecting the connector to the thermostat and start the car-see what the gauge reads-if it zeros, the car will zt least run. if it still max's out-then the gauge is getting input from a second source- a short?

[jwendell]

Originally Posted by xj31

I have seen this before and it was actually the body computer.I still have no idea how because according to schematics,it is not supposed to have anything to do with the temp gauge.I had the luxury of an identical jeep to swap test parts from.The bcm was just a guess after trying the sensor,gauge and pcm.

is there anyway to test the body computer? it's been at the dealership for 1.5 days now and they still cannot figure anything out!

[smichael]

sorry - meant the temp sensor. I had a similar prob with a 93 gr chkee
the gauge would read zero intermittently. I did try changing the sensor but it made no difference. My prob was less bothersome since it read zero instead of hi- it still does this but very infrequently(occurance has leesened,but don't know why)-not enough to waste money having a dealer try to solve it.

Originally Posted by jwendell

do you mean disconnect the connector to the temp. sensor?? i've tried disconnecting from the sensor and still reads high. I was also told that if i turn the key on without starting and the gauge reads high, the thermostat has nothing to do with it...thanks