Vehicle is a 2002 Chevy Avalanche, 5.3L V8, 113k on the clock, I bought it with 110k on it. Since owning it, the fuel filter has been replaced, and the fuel pump module and lines have been replaced.
Cruising at about 45mph this morning the check engine light came on. Codes are as follows
P0442
Pending Codes:
P0131
P0151
P0442
From what i've gathered, P0442 is EVAP small leak detected, P0131 is HO2S Circuit low voltage bank 1 sensor 1, and P0151 is HO2S circuit low voltage bank 2 sensor 1.
I don't know the inner workings of this truck well enough currently. I'm assuming that both of the 02 sensors in question are in the exhaust manifolds, although I have yet to stick my head in there and look. I figured I'd get some info from the GM techs on here before I started screwing with stuff. Does low voltage indicate that the sensor is going bad? What is the most common place for the EVAP system to leak from? Yes, the gas cap is on tight. Are these codes usually related to one another? The truck is originally from Ohio and they don't really do inspections over there so it'd be safe to assume that most of the parts are original.
Thanks for any help
You didnt by chance put E85 in it did you?
mitdr774 wrote:You didnt by chance put E85 in it did you?
no sir. it had about 1/4 tank in it when the CEL came on. I've been running 87 in it just as the owners manual states. bad gas maybe?
should i reset the codes and see if they come back?
Generally I'd take a shot at the o2 sensors but Bank 1 sensor 1 and bank 2 sensor 2 are both of the sensors pre- catalytic converter in the exhaust manifolds.. Seems like something has gone wrong.
Unfortunantly without professional diagnostic tools you are pretty much left making guesses..
If I were you I'd start off with a new gas cap just for S-N-G's. If the code comes back on then what you would need to do is go to a shop that has a smoke machine, basically they plumb a smoke line into the Evap port and look for the smoke escaping through the evap components. Generally Evap components are dealer only items and it would be counteractive to just start replacing parts that others have in a last ditch effort..
As for the 02 sensors, they are only pending codes.. I assume low voltage is what they are returning to the PCM as the A/F signal.. If they arent seeing the Evap flow through the intake system because its leaking out than that could skew what the 02 sensors are seeing in the exhaust stream aka low voltage.
So get the Evap leak taken care of and see if that will fix the 02 problem..
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Gas caps almost always result in a large or gross leak code.
Not the P0442 small leak detected.
For both o2 sensors to have a low voltage signal as a pending code would tell me to clear the codes, and see what comes back. You are most likely going to need to have a smoke test done to find that leak, but hopefully the pending o2 codes wont come back. I would almost say it is a wiring issue to have both primary sensors read low voltage
