A little background first: I recently changed my clutch, and in the process I had to remove the headers. I replaced the drivers side 02 sensor because a bare wire was showing from rubbing on the frame. The pass. side O2 sensor looked fine and had no issues. I'm also not running cats but still have the rest of the emission hooked up (AIR pump)......this is on a 99 Corvette.

So now I'm finished with that and I'm driving the car. I keep setting a P0154 DTC. Besides the check engine light, the fuel mileage is down about 25%. Also, I can hear what sounds like the AIR pump running constantly. The light will come on about 5-10 minutes after I've been driving. If I clear it, it will come back on the next time I drive the car.

I don't know if the AIR pump running constantly is causing the P0154 or if the code is causing the AIR pump to run.

I did some monitoring with HPtuner last night:

So bank 2 02 sensor is pretty much constant at around 450mV, which according to the manual would be a problem..."inactivity" or something to that effect.

However, Bank 1 is cycling between 0 and ~500mV (don't remember for sure...but diffenatly down to 0) Also, the Bank 1 LTFT is maxed out at 25 (If I turn it to closed loop) if I reset the LTFT and turn on closed loop it quickly goes back to 25. It also starts missing and running poorly in closed loop. The bank 1 injectors also begin to increase in duty cycle.

So I'm thinking my gas mileage is down because its not going into closed loop mode and because the computer is adding a bunch of fuel.

I checked the wires connected to the 02 sensors and all looked well.

Anyone got some more ideas or more checks to do?

 

Hi--rather hard to diagnose but as you probably know P0154 is referring
to bank 2 sensor 1--so pass side--You said that bank 1 is oscillating and that is proper--however bank 2 is not and is locked at 450 MV--which is not---Reading the repair procedures --pretty much calls for replacement of the 02 sensor and the drastic repair of replacing the ECM---Don't know why bank 1 LTFT's would go whacky as well as bank 1 duty cycle--Unless because bank 2 is inoperative in closed loop and bank 1 is trying to compensate for fueling on both sides ---don't know-- As far as the AIR pump is concerned it normaly only kicks on intermitantly at start-up--if it is staying on all the time that could cause fueling errors I'm sure--I have mine turned off and the only true way that i could find to turn it off was to dis-connect the pigtail at the pump itself--I tried everything and made all the comp. adjustments and it still kicked on--so i unplugged it--I also plugged or capped both side air tubes at the headers to eliminate any possible exhaust leaks--
The air pump being on all the time would make the 02's read false lean and the ECM would try to add fuel to correct
Wish i could be more help--but try unplugging the AIR pump 1st
Also check the 02 fuses

 

im new at this stuff but i am a helluva trouble shooter. my theory is to always do the cheapest thing first

do you have enough miles on the car for it to be possible for a bad O2 sensor? Try to find a good used one and swap it out or if time is a concern get a new one?

ECM bad $$$$ again i would get a good used one and swap it out

also ecm's are famous for corrosion on the connectors and....i just remembered the electrical grounds on the chassis of these cars corrode terribly and give all kinds of strange errors. the C6 was upgraded bigtime on chasis body ground connections because it was so wide spread on the C5

these cars do not like wet weather

You probably know all this but hope it helps a little in the Hope department