2012 TC wouldn’t go into overdrive

[JerryP]

Weird thing happened. On my 2012 TC Taxi with 330000 mi, check engine light came on and it wouldn’t go into overdrive. Just 3rd gear. I took it to my mechanic and he came up with code P0171, too lean fuel mixture. Said maybe a vacuum leak and cleared the code. Then it started shifting as normal going into overdrive like nothing happened. I’m waiting for the code to set up again and I’ll clear it myself to see what happens. I don’t see the connection but strange stuff happens when you’re over 300,000 miles. 

[Fifty150]

So your mechanic cleared the code, did not perform additional diagnostics, and that was it?

[JerryP]

Well, he told me which code w came up (P0171 lean mixture) and told me it might be an intake manifold but it was 5 minutes before closing. After he cleared the code overdrive came back and it ran well until today. I checked the code myself (same code) and after I cleared the code overdrive came back again. I’m thinking this might be s computer problem rather than a transmission problem. 

[Fifty150]

Quite the conundrum. Apparently there is no prior forum post to reference.  Which makes this unique to you.

[JerryP]

2 hours ago, Fifty150 said:

Quite the conundrum. Apparently there is no prior forum post to reference.  Which makes this unique to you.

UPDATE:  Today, I’m not getting any trouble codes but a couple of times now I have lost overdrive. Stopping and shutting off the motor for a couple of minutes and it’s back just fine. This has to be electrical rather than mechanical. But I’ve been wrong trying to diagnose later model cars before. 

[MtHamby]

Hi I have encountered the same problem with my connect and I was wondering if you ever figured out what was wrong?

[Schmittey]

My son's is doing the same thing but he has a rich code. We clear it and it will be good for a bit. Changed the O2 to no avail.

[peeweedan9]

I am also experiencing this same issue. O/D cuts out and leaves the transmission shifting hard into 2nd and 3rd gear. "System too lean" P0171 code still presenting itself even after replacing the intake manifold, manifold pressure sensor, both O2 sensors, MAF sensor, air filter, spark plugs, coil packs and a few other things I can't remember.

 

It used to be very intermittent, but now it happens after about 7 min of driving, every time. I keep an OBD reader, that can erase the codes temporarily while driving, that I use on longer trips. Turning off and on the car at stop lights also resets whatever is going on with the transmission.