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Odd temp gauge issue???

R

RCP Phx

NAXJA Forum User
Location
Phoenix,Az
2000XJ-Temp gauges falls "semi-randomly" to 110*(not zero) under normal driving.It doesnt seem to do it at slower speeds.If you are crusing and it drops,it will come back to temp like if you pull up to a light.As soon as you start going again and get up to speed it falls off again.On the freeway it will fall off but comeback sometimes if you decrease/increase speed(seems a little "load" sensetive).
 
You don't have an actual "temperature gauge sending unit". The PCM feeds info to the gauge from data it gets from the CTS, coolant temp sensor.

That said, that is quite a radical drop, from "normal" of 205~210 down to 110 degrees. I don't think a screwy thermostat could give you those readings, or even a stuck fan--either efan or mechanical.

I guess I would try swapping the CTS--although I hate throwing parts at a problem. You could try cleaning the contacts at the CTS and the PCM.
 
Its definately electrical,Ive driven hundreds of miles at a time while its doing this.
 
Do you have an OBDII scanner? If you can monitor the temperature in the ECM you will be able to determine if the problem is on the leg between the sensor and computer, or the leg between the computer and the gauge. It sounds like a loose or dirty connector to me, probably on the gauge side or else you would notice engine problems when the temperature "dropped"
 
$0.02.

-Have someone watch the gauge, key on, warm engine, engine OFF. Wiggle the cables at temp sensor and by PCM. Watch for changes in reading.

-Pull the connector off the sensor, wrench it loose 1/8 turn and snug back down to proper torque, couple of times. reseat connector couple of times. retest.

-J/Y sensor to retest.

-How fast does it change readings?

-Is coolant level in the recovery tank going up and down - hot engine to cold engine?

Good Luck,
Orange
 
It changes in a second or two(up or down),I'll try the scanner and see what is shows!
Again,its not the thermostat(that wouldn't even be possible to go from 210* to 110*).
 
Mine does the same thing. only thing i have looked at so far is the cts on the water pump. took it off while at 210, watched the needle drop. put it on, needle came back up. this was while it was working correctly.

mine has an additional issue, it will drop to 0 at times. have yet to check the plug during this time (figure when it does it, if i take it off, and put it back on and it works, issue more then likely is the sensor).

have the efan override, so worse case i will use that if i am concerned (until i can get in and get at it)

the
 
Just went and pulled the plug(seemed alright),put some electricaly conductive grease on it,hooked up the scanner and went for a ride!Couldn't get it to do it,we'll see.Maybe just the connection!
 
my 97 has been doing the same thing, I have a new CTS on the way so I'll let you know if that fixes it. its really more annoying than anything else, especially since any time it happens it drops into open loop
 
birchlakeXJ said:
Dielectric grease is your friend for all of your sensor connections. Let us know if the fix is permanent.
Click to expand...

Dielectric grease is not the same as "conductive grease" and is used like on spark plug terminals and water-proof connectors(not the actual contacts).It shouldn't be used for actual contacts.
 
Last edited:
I don't see where you would use conductive grease with a two-wire CTS. Putting it on the connector might encourage shorting, and since it grounds through the wire instead of through the shell you wouldn't gain anything from putting it on the threads either.
 
Ox Guard is a conductive grease that should be used CAREFULLY to avoid shorts. Dielectirc grease is purposefully NOT conductive for use with connectors. It can and should prevent corrosion.
 
sjx40250 said:
Ox Guard is a conductive grease that should be used CAREFULLY to avoid shorts. Dielectirc grease is purposefully NOT conductive for use with connectors. It can and should prevent corrosion.
Click to expand...

Exactly!

Clean the contacts, treat with dielectric grease that will prevent corrosion from forming, seeing as how water entry OR corrosion are 99.999% of the problems you will have with the harness.
 
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