jophilpott

I started up the Tahoe today after a day of driving and the check engine light came on. I scanned the DTC codes and it returned P0040. I googled this and it says the oxygen sensors have swapped banks or something like that. Anyone know how this could have happened or how to fix it?

Thanks

in2pro

The first thing I would check based on your statement you came back after a long trip is to get under the truck and inspect the wiring, make sure nothing got next to the exhust or melted.
Its also possible its totaly unrelated, I'd inspect everything thatit suggest, write it down and clear it and see if it returns.

Code P0040

Possible Causes:

Crossed Heated Oxygen Sensor harness connectors
Wiring swapped from one Oxygen Sensor connector to the other
Wiring changed at the computer connection or in the related harness

Diagnostic Help:

This check engine light code is caused by swapped wiring or connectors of the upstream Heated Oxygen Sensors. This would have to be the result of a previous repair, so be sure to check the vehicle history. You may also use the "Get Help" link if you need specifications or have any other related questions. Remember to refer to an appropriate manual for specific instructions.

jophilpott

Yea I found that on google. But this happened after normal daily driving. It also has been taking a few extra cranks to turn over since the light came on.

in2pro

Im looking thru the shop manuals and not seeing anything listed for troubleshooting the p0040 right off the bat,but will keep reading over the weekendand post what I find if XZ doesnt respond before then, its possible its a ligit error for the heated o2 sensor it just set the incorrect code for what it interpreted.

ZX1100F1

P0040 is not a possible DTC for an 07 Tahoe, is there a chance that you have mis-read the code?
Other than the SES light did you notice anything out of the ordinary with the operation of your Tahoe?
I take it that you used the scan-tool to reset the DTC, has it returned?

jophilpott

I used the Diagnostics Tool in the Edge Evolution Tuner menu. Returned code P0040. After a fill up today the light shut off on its own. For about 2 days it was taking a couple extra cranks before the Tahoe would turn over. Since the fill up this morning the CEL has not come back on.

in2pro

Has the starting inproved since the light went out?

jophilpott

Everything seems to be back to normal now. Perhaps it was crappy gas?

mary900

I've had the check engine light come on when I didn't tighten the gas cap appropriately. I was told by my dealer that not tightening the gas cap properly messes with the oxygen sensor.

After re-tightening and driving a few miles, the light went off. I'm guessing you double-checked that already??

jophilpott

I checked that first thing. My wifes Acura does the same thing. I just took a quick trip to Lowe's and on my way home, CEL came on again, code P0040 again.

Ugh!