I have a 96 nissan maxima. 3.0liter. It has 104k miles. Well kept. snap on scanner tells me that O2,egr,evap monitors are not ready. It stalled two times on decelerations with the ac on and no other stalls as of this message. the only trouble code was p0172 and no mil light. Spark plugs are carbon fouled. Customer claims that the battery has not been disconnected, although I feel differently. Has anyone come across this one before?

i would agree that the battery has at some point been recently disconnected, that is the only reason for the "not ready' status codes. I would put a fewdrive cycles on the car and re-scan it. My guess with what you posted above would be an ignition problem in which the MIL was on and the customer probably disconnected the battery to get rid of it. were there any other hard codes besides p0172??? also what is the misfire count on each of the cylinders???

our scan tool could only read generic codes, so I couldn't read misfire counts. A veteran nissan tech we contacted said" those o2's were recalled" So that's my best lead yet. Thanks.

02 sensor will not cause carbon fouling or vehicle stalling. like i said, put drive cycles on the car to bring the readiness status online, then if the 02 trips the MIL you know its bad but it is not going to be the only culprit.

the only possible way that the 02 could cause the symptoms would be if it were throwing lean codes telling the pcm to dump in excess fuel...that might explain the carbon fouling hard to tell without being there sorry