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I have a 99 jeep grand cherokee 4.7 that is overheating whenin traffic or at a stoplight or drivethru. i have a check engine code p01491 . i have replaced the fan relay.i hhave jumped the fan it works . The fuses are good . i have no power a the relay connector or by the pcm . could it be a bad wire on the pcm connector or the pcm ? are there any other sensors that could cause the fan not to come on? .any help would be great.

Posted / edited by AnonymousUser on : 15-01-2018

Answers :

The relay gets power on the gray wire from a 40amp fuse. The relay is grounded and gets a power signal from the PCM on the dark blue and pink wire. The PCM signals the relay if the engine temp reaches 220 degrees or the ac is turned on and it works.
You would need to have a scanner or the means to read engine temp to find out if the computer is signaling the relay on when the coolant temp reaches 220 - 225 degrees.
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