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Discussion Starter #1
My trusted mechanic has had my sons 2007 Cobalt (118k) for 2 weeks and is stumped.

The car seems to have trouble shifting (auto) into the next gear and will rev past 3k until you "feather" the gears into place.

The usual fuel filter replacement etc. was done and I don't believe the car is giving up any codes. He seems to think the transmission itself is fine as it has the problem with all the gears?

I didn't pay much for the vehicle but would like it to last awhile for university use.

We have had it for 5 months and so far I have:

4 dealer recalls (locked ignition key etc.)
Replaced signal switch
Replaced driver door speaker.
Fuel filter and lines replaced.

Any help would be much appreciated, thank you.
 

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May just be a bit of corrosion on the BCM P1 and P2, just unplug them and re-plug a couple of times and make sure they are well seated. Maybe add a little dielectric grease to keep the moisture out.

 

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If he has a good code reader, there should be a communication code set between BCM / TCM and cluster.

Maybe also flip the fuse in the upper left corner called ECM/TCM in case it has corroded too!!!!

 

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A communication code would just verify what I think the OP's problem is. It wouldn't confirm but would sure tell this is the right track to pursue.
 

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Discussion Starter #9
Picking up today as it appears to be fixed.

The mechanic said "transmission Range Sensor" problem I think.
It wasn't allowing the vehicle to shift properly and over revved.

Time will tell, picking up today or tomorrow.

BTW, thank you for the suggestions.
 

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''Transmission Range Sensor'' , I think you will be visiting your mechanic soon. This sensor will not make your transmission shift hard, in fact once the shifter is in drive, this sensor doesn't do anything other than to tell the CPUs that the car is expected to go forward.
 

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Discussion Starter #11
Actually my mechanic also said it should not effect it. He had a transmission guy come by and they thought it wouldn't hurt to try everything. He cleaned all contacts and re-seated everything possible but until the sensor was switched nothing helped.

Ran the car hard all over town and took on highway - flawless.

Time will tell...
 

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So they did re-seat the connectors on the BCM!!!???
 

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I don't want to here but I don't want people reading this thread when they have the same problem and think that changing that sensor is the solution. As you can see in this diagram the sensor is only there so you don't accidentally start your car in gear. No connections are made during reverse or forward gears and signal doesn't even go to any CPUs including the (TCM) Transmission Control Module. I'm sure it was just a coincidence that everything worked after this change or he cleaned the BCM contacts at the same time and doesn't remember. Or maybe he doesn't want to admit to himself or be embarrassed that it was as simple as re-seating connectors and that he took so long to fix it.



Hope your son enjoys is University wheels like both my daughters did, they are a great ''A'' to ''B'' daily driver. My youngest is still enjoying her 07, my oldest just got her new Buick Encore after 6 years with a Cobalt.
 
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