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Pontiac g6 TC & ESC limp mode

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  1. I own a 2010 Pontiac g6 2.4l ecotech and over the course of a little less than a year my car has started too randomly go into limp mode while I’m driving above 55 mph and I lose power until I rev my motor a little bet and then stomp it and drive it through two gears before it returns too normal. I ended up getting it looked at and I was told it was the crank shaft position sensor. I had it changed and it was fine for 45 mins after I left the shop then it started right back up. I then replaced it my self two more times because it kept throwing the crank shaft position sensor code. I drove it back from work one evening and it was completely in limp mode and it wouldn’t come back so I parked it and it didn’t start again. Took it too the shop
  2. they said I need a new motor I get the new motor they install it and the same day that I got my car back the exact some problems continued too occur with the traction control and emergency stability control would shut off and put my car in limp mode. Along with that it gained a new problem since I got my new motor which is after it warms up it will drop too 0 rpms in the gauge cluster while I’m driving and or completely shut off if I’m stopped somewhere when it drops. If it drops while I’m driving the cafe just stalls for a second and then continues underpowered without me knowing exactly how many rpms I’m running. It then takes like 3-5 second longer for my motor too turn over when it drops too 0 rpms if my car shuts of when it drops. But after your drive for about 30 or 45 mins you can turn my car off and back on and it will run the same way it did before it dropped too 0 rpms on the gauge. Which means just the traction control and emergency stability control sending me into limp mode. Do you have any idea what this could be? I’ve  been fighting with it for months now. It also makes a weird noise when I’m parked and it’s at 0 rpms from the tranny/torque converter area. Any ideas or guesses 
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Posted by: @javy

they said I need a new motor

What did "they" base this on? Compression test? Leakdown test? Low oil pressure? Bad noises?

What problems do codes and data reveal?

From what I was told it was based on a compression test. I didn’t really know if I believed it or not but my cars engine wouldn’t turn over prior to me taking it too get looked at before the engine replacement.

Did they give you the specific compression values they found?

I don’t remember exactly since it was 6 months ago but i believe they said it had either low or no compression

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Posted by: @javy

Well in theory if the engine was shot and no longer any good do you have any ideas of what would cause the same problems with my current engine that replaced that one?

I'm assuming it was not an actual brand-new GM crate motor, I don't know if anything like that is even available and even if it was the cost would be prohibitive. Was it a rebuilt engine, or maybe a used one from a junkyard? You'd need to check compression on the replacement engine to see if it's OK. If compression checks out it's time to start recording and analyzing live data to see what's going on.

My suspicion is that the original engine was not actually worn out since replacing it did not fix the problems, unless you're really unlucky and the "new" engine is bad as well. More diagnosis is needed.

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You didn't say if the code is CKPs circuit low/high or if it's a CKPs signal code but you're losing your rpm signal and it's a safe bet you have a problem in the CKPs circuit. 

So 1st hook up a scanner (live data) and make sure that the PCM is losing the rpm signal and this isn't an issue in the wiring between the PCM and the tachometer on the dash cluster, or the dash cluster itself.

If you're losing the rpm signal on the scanner you'll want to test the CKPs wiring and you'll want to do it while the car is acting up. You'll need a multimeter and a test light.

Here's the circuit. 

Here's the circuit test procedure (it's the same for the 2005-2010 Pontiac G6):

 

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