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If that is the same as current, then it is the cause of your shifting issues.
Yes, confirmed is the same as current on my scan tool. That's crazy. I've never seen a lean condition code cause a car to not shift into overdrive. Just run bad and use more gas.
Thank you very much! I'll go throgh and clean the MAF, test fuel pressure, and smoke it tomorrow. I got lucky with my 97 Ranger last week and a MAF cleaning cleared the same code. (Fingers crossed)
Don’t dismiss P0171 as a vacuum leak. There are other possibilities. It means “Fuel Trim System Lean”, i.e., the system thinks the system is defaulting lean, and that the (successful) adjustment to get to the correct a/f is excessive.
Do you ever run E85? NOT a bad thing. Good stuff. But knowing that can help diagnose. GM FlexFuel very rarely get confused about the ethanol percent in the tank. That can result in P0171 or P0172. AVOIDING THE USE OF E85 WIILL NOT PREVENT THIS PROBLEM, so don’t let anyone blame the use of E85. There’s at least one TSB on it. Ask me how I know.
But I wouldn’t worry about that yet.
I would first verify correct fluid level in the transmission. Then I would clear the codes and see if the hard shifting stops (at least until the code sets again.)
BTW, I definitely agree with previous advice to clean the MAF sensor and throttle body.
Also, a bad #1 O2 sensor can give you trouble with a/f readings.
PSA, alway shut down when refueling, but especially with a GM FlexFuel car.
It's not the lean condition that's messing with the shifting, it's the presence of certain codes.
Gotcha. I was able to clean the MAF but that didn't clear the P0171 code. I also found the intake tube into the airbox was completely disconnected so it's been sucking dust for God knows how long. Will test and replace the MAF and continue to troubleshoot that code.
While test drving it this morning, I did get new codes, and the CEL came on.
The ECM now has P0700 (Trans Control Sytem (MIL Request) in both pending and confirmed states.
The TCM now has P0842 (Trans Flud Pressure Sensor/Switch "A" Circuit Low) in both pending and confirmed states.
Don’t dismiss P0171 as a vacuum leak. There are other possibilities. It means “Fuel Trim System Lean”, i.e., the system thinks the system is defaulting lean, and that the (successful) adjustment to get to the correct a/f is excessive.
Do you ever run E85? NOT a bad thing. Good stuff. But knowing that can help diagnose. GM FlexFuel very rarely get confused about the ethanol percent in the tank. That can result in P0171 or P0172. AVOIDING THE USE OF E85 WIILL NOT PREVENT THIS PROBLEM, so don’t let anyone blame the use of E85. There’s at least one TSB on it. Ask me how I know.
But I wouldn’t worry about that yet.
I would first verify correct fluid level in the transmission. Then I would clear the codes and see if the hard shifting stops (at least until the code sets again.)
BTW, I definitely agree with previous advice to clean the MAF sensor and throttle body.
Also, a bad #1 O2 sensor can give you trouble with a/f readings.
PSA, alway shut down when refueling, but especially with a GM FlexFuel car.
Thanks for the info. I'm not sure on the E85. I bought the car yesterday and it's got 150k miles on it. I'm about to go back out and check the fluid level after these new codes popped up on a test drive this morning. (P0700 in the TCM and P0842 in the ECM)
Check for chaffed wires near the TCM , if the transmission fluid is full, consider replacing the TFPS and the shift solenoids inside the transmission cover on the drivers side.
there might be melted connectors or other issues with the transmission
Check for chaffed wires near the TCM , if the transmission fluid is full, consider replacing the TFPS and the shift solenoids inside the transmission cover on the drivers side.
there might be melted connectors or other issues with the transmission
Will do on the wiring. I just checked out a video on replacing the sensors and solenoids. I can handle that job in probably half a day. Worth a shot! Also thinking I'm going to pull the pan and see what it looks like in there.
08-27-2024, 10:12 PM
