Took my OBW 2001 72k in for oil and coolant change because the coolant was a bit low and looked grubby to me. This gives a known starting point to look for more cross contamination that might be a leaking head gasket.
In the weeks prior, had the CEL light come on a few times (then going off after a few stop start cycles) and assumed it was the gas cap thing as it always went away when I filled up or tightened the cap. (I only found it loose once.)
The CEL was on when I went in for the other work and I had them pull the codes.
Here's what it had in it (recent at top):
P0136 O2 Sensor Circuit Range/Performance Problem - Malfunction (Bank 1 Sensor 2)
P0500 Vehicle Speed Sensor Malfunction
P0512 Starter switch circuit high input
P0151 O2 Sensor Circuit Range/Performance Problem - Low Input (Bank 2 Sensor 1)
P0154 O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
They imediately went to "we don't have that part if you come back on Tuesday we can do the swap for $250" I delayed that as it would be sort of useless in the face of a 3k bill for the gasket (would probably junk the car if that's what the problem is).
Having gone through the O2 sensor BS before, it does not seem the same to me. For one, last time there was no CEL at all, but all sorts of engine power or hesitation issues. Given the fact the O2 sensor has a pretty integral part to play, I am leery of just replacing it. I think it is the same one as replaced last time, so it's only 3 years old.
So I am curious as to if anybody has suggestions of other stuff the codes could represent other than the O2 sensor. The ODB2 code set seems to imply there is two "bank 2" sensors, so this could be the other one failing, but those codes are shared amongst many models so there could be one in front.
So...
What else could this be?
How many sensors are there (up front)?
Is $250 a high price? ($100 part, rest labor)