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Engine Coolant Temperature Circuit Sensor Low Voltage

98XJSport

98XJSport

Destiny is the rising sun
Location
Western Maine
Thats the code Im getting, 98 xj 4.0. P0117

Funny thing is it only happens when I go in reverse. Then the temp guage maxes out, throws CEL, then goes back to normal. It's been killing my gas mileage I think, and a lack of power. I have replaced the sensor, no help. Tried cleaning it, as I think it's self grounding, no luck. Anyone run into this or have any suggestions?
 
No thoughts? Best Ive got is wait for warm and start tracing wires...
 
It only happens when you hit reverse? Do you mean the instant you shift into reverse the guage spikes, or once you shift, it begins to climb at a steady rate?

Kinda sounds like a crossed/shorted wire somewhere....
 
I shift in reverse and start to roll backwards and the guage goes up pretty fast. As in when you shut the vehicle off when warm, and turn the key back on and the guage goes back up to temp. That fast. It's not instant, but a few seconds after I hit reverse. But I can't think of anyplace the reverse linkages go near wiring for the coolant temp. sensor?
 
Also forgot to mention that this all started happening after I changed my Alt. to a GC alt. and put on a new s. belt. For what it's worth...
 
Nobody? I figured this might be a common problem, guess not...
 
Jeep did it again, this time it wouldn't let me clear the code with my scanner. Let it sit for a few days then it would let me. So it's my assumption that whatever was causing the code was not intermittant at that time. Checked out the connector, nothing. It's been to cold to check any further into the wiring at this point, hopefully soon.

Anyone have any thoughts as to what could be causing this? Any place the reverse linkages come near the wiring?

I wondered if the alt. could have an effect, but thats a stretch...
 
98XJSport said:
Also forgot to mention that this all started happening after I changed my Alt. to a GC alt. and put on a new s. belt. For what it's worth...
Click to expand...

What is a "GC ALT"?

Reverse Engine/transmission torque could be moving wires in a direction forward/engine torque does not. I would definately look for a wire in the harness grounding out.
 
grand cherokee alternator

Also when I say in reverse I mean just shifted into reverse, actually moving or not doesn't seem to have any bearing...
 
Ok pulled out most of the wiring harness and traced wires, found that the wire rubbed through the insulation betwen the firewall and the fuel rail. Little bit of tape, and no CEL after an hour of driving, and a couple times in reverse. Hopefully that solved it, although not sure what reverse had to do with it. But as long as it works... Im not complaining.
 
98XJSport said:
Ok pulled out most of the wiring harness and traced wires, found that the wire rubbed through the insulation betwen the firewall and the fuel rail. Little bit of tape, and no CEL after an hour of driving, and a couple times in reverse. Hopefully that solved it, although not sure what reverse had to do with it. But as long as it works... Im not complaining.
Click to expand...

Either reverse was moving the wires and the frame just the right way to close that short but only in reverse, or that wire was involved (hot) in the TCM/ECU/AW4 controls when switched into reverse.

Glad you found it. Those are the worst kind to try and find and trouble shoot! Congrates!!!!!:worship:
 
By the way, just be glad it is a 98 you are working on and not an 85 with severly corroded wiring like mine.:eek:
 
Well it seemed to have more power, but I reset the ECU and drove normal so I didn't really get on it to tell. Plus my DD is a sportly light 6 speed car, so its hard to judge. And I will fill up the tank tomorrow and drive it to find out gas mileage. But I can't see how it could do anything but hurt the mileage.

Either that or this sensor being screwy is what burned out my upstream O2, and most likely damaged the CAT. Which could be giving me the bad performance.
 
Well did a gas mileage check. Before I was getting 12-14 MPG. Over the last 3 days I got 16.5. That is not figuring in for 31" tires, plus I was in 4x4 at 40 mph more than half that time. Based on that I think the power is ok, too.
 
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