Q: P0642 2006 Jeep Grand Cherokee

asked by on August 18, 2017

I am getting code p0642 along with u1408 and u140c. The U codes were able to be deleted but p0642 stays. It seems there is an issue with the 5 volt reference from what I've researched. What steps should I take before breaking off and buying new ecm?

My car has 138000 miles.
My car has an automatic transmission.

The low reference voltage may be from one of the engine sensors like the throttle position sensor shorted reference signal. You can try to disconnect one engine sensor at a time to see if code P0642 goes away and the sensor code may come up but if code Po642 goes away then you know that sensor is the shorted sensor. If after disconnecting sensors you continue to get the code P0642 then you will need to look at replacing the ECM.

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