gsujake

I have a new to me 1998 Jeep Cherokee. 110+K and seems to be in great shape, but there is a problem. The temp gauge goes crazy randomly. The sensor was replaced prior to me purchasing it because of the problem, and it did not fix it.
I do not believe that it truly is overheating (I drove it 3 hours today and it was fine).

Symptoms: The check engine light is on all the time
- The gauge will read 110 one second, then shoot to 260 (check gauge light comes on) then shoot back between 210 and 110 randomly. It bounces all over the place.

I have attempted to search and find the answer but since it's not a 1996 or older, I am out of guesses.

Here is a picture of the sensor that has been spliced, rewired and replaced




Please watch entire video

I removed the the cover over the wiring harness along the fuel rail and found this

CCKen

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gsujake

what I mean is, most problems I found that were very similar were 1996 and earlier. I guess they had two sensors, one at the thermostat and one at the back of the head on the driver's side. I guess '97 to '01 do not have the sensor at the back of the head.

Thanks, I will look into that.

Could it be that when they spliced the wires, they hooked them up backwards?

CCKen

Could be. But I don't think that would cause an intermittent temp gauge reading.

CCKen

Here's some tests I did using a digital Voltmeter and a safety pin to back probe the wires in the connector. Pin 2 voltages may vary based on coolant temp at the time of testing. Give it a try.





Small safety pin for back probing:





Example of back probing the MAP sensor connector.





Insert the safety pin along side the wire until it bottoms out in the connector, then connect your meter to the safety pin (+) probe to pin, (-) probe to battery negative post.

gsujake

Updated

Thanks for the help so far. I don't have a voltmeter, I will try to obtain one tomorrow evening.

extrashaky

The check engine light may or may not be related to your temp gauge issue. You should read the codes and find out what code it's throwing. Some local auto parts chains (O'Reilladvancedautozonapaquest) will read them for you for free, or you can pick up a reader, or you can order a bluetooth adapter and read them with the Torque app on your phone. If you're gonna own a teenage Jeep, you really ought to have some way to read the codes it's gonna throw at you.

If you have a Harbor Freight near you, you can get one for free right now. They're doing their "three free gifts" coupons for Father's Day, and one of them is their little $15 multimeter. It's not a great meter by any stretch of the imagination, but it'll get the job done if you don't want to spend any money. Here's a link to the coupons:

http://images.harborfreight.com/hftw...coupon2015.jpg

There's also a 20% super coupon in there in case you want to pick up one of their code readers at a discount.

gsujake

Got it fixed. Here was the problem (CCKen called it), I removed the cover over the wiring harness for the sensor and injectors, and the last pic shows what I found. I removed about 4-5 inches of the insulation and taped all of the wires and the problem is cured.

Easiest fix I've ever had and this could have given me fits! thanks guys