Hard Shifting and Hesitation when Car Sits for a Period of Time - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 2 (permalink) Old 05-24-2018, 08:08 AM Thread Starter
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Hard Shifting and Hesitation when Car Sits for a Period of Time

My 2007 Chevy Cobalt (auto trans) shifts hard and hesitates, only does this when car sits for a half day or more. Took it to a shop they drove it around for a couple of days. They had no hard shifting or hesitation. They could not figure out what was wrong with it. No check engine light. Picked up my car this morning and did the hard shift and hesitation again. Any suggestions?
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post #2 of 2 (permalink) Old 05-24-2018, 10:26 AM
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Clean and re-seat connectors on ECM, TCM and BCM. I suggest you do this one module at a time so you know which one is causing loss of communication. You may not have a CEL but I'm sure you have a pending "U" code or in history. Once you find which connector was causing it clean again and add dielectric grease. I would start with the 2 blue/gray connectors on the BCM, this is where the GMLan gets amplified clipped and restored. You may also want to check your oil pressure sending unit to make sure it's not leaking oil and then running down along the wires all the way to the ECM. Oil in a connector tends to wreak havoc.

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