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Hey guys I've really hit a brick wall here and have no idea what to do anymore. Before anyone sends me links to other threads documenting hard downshifting and P0171 I have scavenged quite literally every thread on these forums with anything to do with either lean bank or downshifting and I am desperate for original help. What has been happening is I have been having intermittent hard downshifting every time I drive the car over a long distance followed by a Lean bank 1 code. The downshifting goes away until the next time it decides to act up. This has been happening since December 12th. I have assessed every major culprit I can think of and have replaced Cam position sensors, replaced the MAF and the wiring harness going to it, have replaced the intake gaskets, and have run heavy injector cleaner through the fuel injectors. None of this seems to have done anything to cure the issue. Unless anyone tells me otherwise, I'm down to the O2 sensors or ECM. I've also heard that sometimes changing the battery can create miracles but I really am not sure. My gut feeling is that it is electrical since it is so intermittent. I did a reading on the O2 sensors and they read fine but I went to unplug the upstream and I couldn't get it out so maybe it could be burnt up and fused together? It wouldn't be the first time that's happened to me. Either way I haven't hardly driven the car since and me nor my mechanic know where to go from here. I called GM support and they were no help and my local GM dealer claims they have techs that have worked on them but won't allow me to ask them anything unless I pay $125 just to schedule an appt with them. If anyone has any idea or knows anything about this I would VERY appreciate it! I recorded the issue live in my last vlog so this may help :
 

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You say you replaced the Cam position sensors, but id you replace (or mean) the cam actuators/solenoids on the front top of the engine?

The cam sensors or on the rear sides of the engine.
 

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You say you replaced the Cam position sensors, but id you replace (or mean) the cam actuators/solenoids on the front top of the engine?

The cam sensors or on the rear sides of the engine.
I did replace the cam solenoids sorry I got the two mixed up. I did not replace the cam position sensor.
 

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Here is the applicable service manual page.

07-09-451 Fuel Trim Lean.jpg

Vacuum leaks are a common issue with the P0171 according to the threads I went through, but cam solenoids are not, and you didn't mention checking the MAP sensor. Readings with the engine not running and at idle are good indicators of problems.
 

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You didn't list any mods, is the car stock?
No but it is not heavily modified either. All I have on it is a Solo axleback exhaust fitted with a magnaflow instead of the big muffler it came with, GM performance CAI, and a sprint booster. I have noticed that when I start her up I get a puddle of water coming out where the axleback connects to the original exhaust system and there probably is a leak there but it's so far downstream I wouldn't think it would really cause all this.
 

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Here is the applicable service manual page.

View attachment 107114

Vacuum leaks are a common issue with the P0171 according to the threads I went through, but cam solenoids are not, and you didn't mention checking the MAP sensor. Readings with the engine not running and at idle are good indicators of problems.
I did not check or think about the map sensor but that could be a possibility. The whole issue is intermittent which makes me believe its a computer or sensor failure. I had an episode of downshifting and lean bank on december 12th, wiped the code and it didn't come back until Jan. 22 (granted I really only drove the car about 5-10 miles at a time in december) but it has frequented much more. If this was a vacuum leak would the car be acting up all the time instead of intermittently? Also would it cause the hard downshifting and a P0700 P2637 codes to happen? I think the 2 codes I listed are byproducts of the hard downshifting and are unrelated but something concerning a lean bank 1 had to trip it all.
 

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Discussion Starter #8
Here is the applicable service manual page.

View attachment 107114

Vacuum leaks are a common issue with the P0171 according to the threads I went through, but cam solenoids are not, and you didn't mention checking the MAP sensor. Readings with the engine not running and at idle are good indicators of problems.
My Solstice is an automatic I forgot to mention. Do automatics have a map sensor or just a maf sensor?
 

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No but it is not heavily modified either. All I have on it is a Solo axleback exhaust fitted with a magnaflow instead of the big muffler it came with, GM performance CAI, and a sprint booster. I have noticed that when I start her up I get a puddle of water coming out where the axleback connects to the original exhaust system and there probably is a leak there but it's so far downstream I wouldn't think it would really cause all this.
Nothing downstream of the cat should cause this kind of problem.

A Sprintbooster? Really?

I did not check or think about the map sensor but that could be a possibility. The whole issue is intermittent which makes me believe its a computer or sensor failure. I had an episode of downshifting and lean bank on december 12th, wiped the code and it didn't come back until Jan. 22 (granted I really only drove the car about 5-10 miles at a time in december) but it has frequented much more. If this was a vacuum leak would the car be acting up all the time instead of intermittently? Also would it cause the hard downshifting and a P0700 P2637 codes to happen? I think the 2 codes I listed are byproducts of the hard downshifting and are unrelated but something concerning a lean bank 1 had to trip it all.
The vacuum leak could be the result of something opening up when it gets hot.

I guess you haven't read the descriptions of the codes, or all the way through most of the threads that discuss these problems. P0700 says that the TCM has requested the MIL. P2637 indicates that the torque data sent from the ECM to the TCM is invalid. Once it is set, one of the symptoms is the hard downshift, so in one sense, P2637 causes the hard downshift. Although in reality everything is probably a reaction to the P0171.

I don't know how long it takes, but the P2637 resets when the ignition is off long enough for the TCM to be powered down and only sets after two consecutive drive cycles during which a problem is detected. So driving it, then leaving it sitting (or probably disconnecting the battery) will reset the pending code so that it takes two more drive cycles to set the actual code. This could make it seem very intermittent.

My Solstice is an automatic I forgot to mention. Do automatics have a map sensor or just a maf sensor?
The fact that it is downshifting makes it pretty obvious that it is an automatic and yes, all engines have both a MAF and a MAP sensor, regardless of transmission,

You need to read the freeze-frame data, and check the sensor values as described in the threads and the service manual.

Also, did you do anything under the hood shortly before all this started?
 

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Nothing downstream of the cat should cause this kind of problem.

A Sprintbooster? Really?



The vacuum leak could be the result of something opening up when it gets hot.

I guess you haven't read the descriptions of the codes, or all the way through most of the threads that discuss these problems. P0700 says that the TCM has requested the MIL. P2637 indicates that the torque data sent from the ECM to the TCM is invalid. Once it is set, one of the symptoms is the hard downshift, so in one sense, P2637 causes the hard downshift. Although in reality everything is probably a reaction to the P0171.

I don't know how long it takes, but the P2637 resets when the ignition is off long enough for the TCM to be powered down and only sets after two consecutive drive cycles during which a problem is detected. So driving it, then leaving it sitting (or probably disconnecting the battery) will reset the pending code so that it takes two more drive cycles to set the actual code. This could make it seem very intermittent.



The fact that it is downshifting makes it pretty obvious that it is an automatic and yes, all engines have both a MAF and a MAP sensor, regardless of transmission,

You need to read the freeze-frame data, and check the sensor values as described in the threads and the service manual.

Also, did you do anything under the hood shortly before all this started?
No I haven't changed a thing. I think there's some real substance with the TCM resetting. All but one time if the car went into a fit of shifting I would pull it over shut it down for a minute or two and it would be normal on the next restart. After it I would restart it lean bank 1 would come on. There were 2 instances where the light just came on with no downshifts for P0171. I don't mind replacing a couple sensors and I think I'll just go pick up a new MAP sensor tomorrow since they're not too expensive. I'll be honest when it comes to reading data and dealing with electronics. I can look and see the obvious things but this feels so beyond me and my tools with it being intermittent.
 
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