Mechanic's Riddle... Random 'dummy light' problem
#1
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Year: 1997
Model: Cherokee
Engine: I6 4.0L
Mechanic's Riddle... Random 'dummy light' problem
I have a 1997 Cherokee SE 4.0 with a 'mystery' problem. Randomly, my coolant temp "dummy light" will flash on and the cooling fan with turn on. The vehicle "thinks" it is overheating, however it is not. The vehicle is running at very normal temperatures.
I have replaced the coolant temp. sensor and the connector. I have paid several mechanics to fix this problem, and a few hundred dollars later I still have the same problem. I have also replaced the forward O2 sensor and the continuity from the cluster to the sensor has been checked. Just installed a new Cat and Muffler.
Does anyone know what else could cause the temperature "dummy light" to come on randomly???
I have replaced the coolant temp. sensor and the connector. I have paid several mechanics to fix this problem, and a few hundred dollars later I still have the same problem. I have also replaced the forward O2 sensor and the continuity from the cluster to the sensor has been checked. Just installed a new Cat and Muffler.
Does anyone know what else could cause the temperature "dummy light" to come on randomly???
#2
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Year: 1996
Model: Cherokee
Engine: I6 Cyl / 4L
My guess would be that you are overheating and the dummy light is doing its job. Could be your cooling system is failing someplace. I would check it carefully.
Good luck.
Good luck.
#3
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Year: 1999
Model: Cherokee
Engine: 4.0
I have a 1997 Cherokee SE 4.0 with a 'mystery' problem. Randomly, my coolant temp "dummy light" will flash on and the cooling fan with turn on. The vehicle "thinks" it is overheating, however it is not. The vehicle is running at very normal temperatures.
I have replaced the coolant temp. sensor and the connector. I have paid several mechanics to fix this problem, and a few hundred dollars later I still have the same problem. I have also replaced the forward O2 sensor and the continuity from the cluster to the sensor has been checked. Just installed a new Cat and Muffler.
Does anyone know what else could cause the temperature "dummy light" to come on randomly???
I have replaced the coolant temp. sensor and the connector. I have paid several mechanics to fix this problem, and a few hundred dollars later I still have the same problem. I have also replaced the forward O2 sensor and the continuity from the cluster to the sensor has been checked. Just installed a new Cat and Muffler.
Does anyone know what else could cause the temperature "dummy light" to come on randomly???
How do you know that the vehicle is running at very normal temperatures?
See if you can get a scanner that displays live data and check the coolant temp when the light comes on and the fan starts.
The fan is set to kick on around 218*F.
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#11
OP, are you checking the temp with a temp gun or anything? To me it sounded like it was happening quickly? Not sure if I read it right though. could be an issue in the cluster as well, sure not common But I have seen it.
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Update on post
Thanks for helping me out with this problem, and I do have some more information....
Live reading of the temperature after running on the highway for 45 minutes was 198 degrees... Except for the brief period of time the light flashes. Then it jumped up to 308 for the second the light flashed. The vehicle is not running sluggish or showing signs of overheating. In fact, the top radiator hose can be touched without burning yourself.
Both O2 sensors, cat and muffler, coolant temp sensor and wire connector has been replaced.
The continuity from the cluster to the sensor was checked as well.
Also, I drove it up to Georgia this weekend and it ran great the whole way, at 75 mph for over 3 hours.
Is it possible for it to be a problem with my ECM??
Live reading of the temperature after running on the highway for 45 minutes was 198 degrees... Except for the brief period of time the light flashes. Then it jumped up to 308 for the second the light flashed. The vehicle is not running sluggish or showing signs of overheating. In fact, the top radiator hose can be touched without burning yourself.
Both O2 sensors, cat and muffler, coolant temp sensor and wire connector has been replaced.
The continuity from the cluster to the sensor was checked as well.
Also, I drove it up to Georgia this weekend and it ran great the whole way, at 75 mph for over 3 hours.
Is it possible for it to be a problem with my ECM??
Last edited by beyondkreativ; 03-29-2015 at 02:46 PM. Reason: forgot something
#15
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Year: 1999
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Thanks for helping me out with this problem, and I do have some more information....
Live reading of the temperature after running on the highway for 45 minutes was 198 degrees... Except for the brief period of time the light flashes. Then it jumped up to 308 for the second the light flashed. The vehicle is not running sluggish or showing signs of overheating. In fact, the top radiator hose can be touched without burning yourself.
Both O2 sensors, cat and muffler, coolant temp sensor and wire connector has been replaced.
The continuity from the cluster to the sensor was checked as well.
Also, I drove it up to Georgia this weekend and it ran great the whole way, at 75 mph for over 3 hours.
Is it possible for it to be a problem with my ECM??
Live reading of the temperature after running on the highway for 45 minutes was 198 degrees... Except for the brief period of time the light flashes. Then it jumped up to 308 for the second the light flashed. The vehicle is not running sluggish or showing signs of overheating. In fact, the top radiator hose can be touched without burning yourself.
Both O2 sensors, cat and muffler, coolant temp sensor and wire connector has been replaced.
The continuity from the cluster to the sensor was checked as well.
Also, I drove it up to Georgia this weekend and it ran great the whole way, at 75 mph for over 3 hours.
Is it possible for it to be a problem with my ECM??
How did you check continuity from the cluster to the sensor? The ECT sensor signal goes to the PCM, not the cluster.
Why did you replace the ECT connector?
Does your radiator electric fan kick on when the temp jumps to 308 degrees?
It sounds like you are getting an open in either in the live ground network wire to the ECT (Brown/Yellow tracer wire) or an open in the signal wire to the PCM (Tan/Black tracer wire).
Inspect the ECT wires where they enter the fuel injector wiring manifold for defects, and inspect the wire loom where it exits the manifold for chafing through to the wires within. There have been a few reports of the loom chafing on the end of the fuel rail.
The ECT Brown/Yellow tracer wire splices in to the ground network inside of the fuel injector manifold. If you can't find any obvious defects in the wiring/looms outside of the manifold, open the manifold and look for the splice. Check it.
If all else fails, wiggle the wiring harnesses while observing the coolant temp on your scanner to see if it jumps.
I could show you how/where to check voltages at the ECT connector but do the above checks first.