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Discussion Starter #1 (Edited)
I was about to get my 06 g6 and which Ive been driving around for a few days with a dealer plate on. It was driving fine until one morning it was a bit colder out then its been. I started driving down my street and at first I noticed my speedometer not moving. Then I could feel once the car was trying to shift into second gear, it started just revving like it was in neutral until i stomped on the accelerator a bit. Once in second gear the speedometer started to work. This happened a couple times and when I finally got up to 30mph my rpms were pretty high like it wasnt upshifting to the next gear at the right time.

This is the same problem that was happening before, and now its happening again with a replaced transmission. Any ideas guys? Thanks!

EDIT: I forgot to mention once the car warmed up, it was shifting fine. I almost think its low on fluid, so annoying to not be able to check it from the engine bay
 

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that would usually mean the the PCM (this is what tells the engine and transmission what to do when to shift etc....) is bad whether it be just the software, or the actual part i couldnt tell you.....
 

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that would usually mean the the PCM (this is what tells the engine and transmission what to do when to shift etc....) is bad whether it be just the software, or the actual part i couldnt tell you.....
The auto transmissions have their own independent controller (tranny control module) though of course it receives most sensor input via the ECM. That's why GM changed the name from PCM to ECM (powertrain to engine).
 

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I started driving down my street and at first I noticed my speedometer not moving.
That may be a big clue. If you mean by that the speedometer needle is zeroed out there are several possibilities:

problem with the vehicle speed sensor itself or its circuit

loss of the signal bet the ECM & the BCM

loss of the signal bet the BCM & the IPC (fretting corrosion issue at the BCM connector is one possibility)

problem with the speedometer needle motor in the IPC

It might be that your tranny control module is intermittently losing the critical vehicle's speed sensor input.

For starters you need to have the DTC's read by a scan tool. But that may well not pick up a bad VSS if it's intermittently bad.

I wonder if whoever replaced the tranny reinstalled the old VSS. Very likely.

I don't even know which tranny you have so I may have just wasted my time responding because as with most issues it depends on the MY, engine, tranny etc.
 

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Discussion Starter #5
Thank you guys for the input!

Its an 06, 4 cylinder with the 4 speed auto.

The car needs a catalytic converter and they're waiting for that to come in. They believe that this may be the problem as to why the transmission is acting up, but I didn't think the two were related at all? I know a bad cat can cause the car to act funny and underpowered but its been driving perfectly fine besides that transmission issue that occurred.
 

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The transmission relies on engine sensor information to know when to shift, most likely the converter is your problem.
 

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The auto transmissions have their own independent controller (tranny control module) though of course it receives most sensor input via the ECM. That's why GM changed the name from PCM to ECM (powertrain to engine).
they still used PCMs on the 06s only the 07 and new V6s for the G6 used seperate ECM and TCMs but i guess i was wrong in figureing hed be getting a V6 so i spose his are seperate but if he got the V6 it would have a PCM
 
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