I just put a trans in my 99 lumina. The trans was out of a 98 Bonneville, and works beautifully. Problem is, after reassembly i have a P0171 code, bank one lean, but the fuel pressure is good, and i cant find a vacuum leak. The ltft sets way high and actually seems to flood the car out in a serious fashion after having had time to set so high. also, it dies while moving and will surge as well.

Today i got the p0135? code which is for a bank one sensor one o2 heater circuit malfunction. any ideas? Also the fuel economy is TANKED. like 10 around town and 16 on the interstate. I used to get upwards of 27 when i drove it and the wife averages around 22 normal.

The EGR pipe could be a culprit in setting the lean code. Sometimes they crack.

I thought if the LTFT'* were high(on the + side), you would be seeing a LEAN condition vs a RICH condition (on the - side).

? its showing lean. the computer thinks its lean, but with the fuel trims that high, and there not being a vacuum leak, i assume its actually running rich, because it runs fine, until the computer jacks the fuel trims way up.

Just thought i would hop on here, i attempted to test the upstream o2 sensor, by pulling a vacuum line and spraying in carb cleaner. the h20s11 didnt go above 0.530v. and the downstream is still by 0.900+ where it stays, im assuming because the mixture is rich.

if youve got a heater circuit code either the circuit isnt getting the 12v or the sensor is bad. i would check for voltage if its there you have to replace the sensor anyway, then you can see if thats the lean problem or you have something else going on.

but even with other things going on, that sensor should peg when i introduce carb cleaner. or at least go above .530

i see mike lurking, any input?

I thought the heater circuit was only used for cold startups? Once the engine/exhaust etc were up to normal temps, the heater wasn't used??

.900 is almost max for that downstream sensor.

heater code comes up when it doesnt fall into expected parameters in a time window. so your right it would have to be set on start up. when my truck did it i had to replace the sensors

but looking at the upstream showing under .500most of the time, but the downstream being maxxed out, i did the carb cleaner test, and the upstream still didnt change. I replaced the upstream o2 sensor and everything seems back to normal. My wife took it to class today, so it will get 100 miles to fully reset all of the fuel trims on its own.