I have a 2004 Grand Cherokee Special Edition with a 4.0 I6. The problem that I'm having is that my temperature gauge has been fluctuating erratically, for no rhyme or reason. It will go from 250*f to 100*f in under 3 seconds and visa versa. I also have an OBDII reader, Tourque for Android (great App), that can give the internal readings right off of the ECU. That too gives me an erratic reading, but it does not always reflect what the gauge cluster is reading.

At first I thought that it was the sending unit so I replaced that along with the thermostat because it was there and cheap. Some mechanics that I have talked to said to try and replace the temperature sending unit again before starting to replace the gauge cluster, PCM or the ECU as they are several hundred dollars a piece. Has anyone seen this problem or heard of any solutions? Any advice is appreciated.

Thanks,
Nick

 

It's entirely possible that you got a bad sending unit off the shelf