Last night the "check engine" light came on. I pulled the codes this afternoon and it said 77 - rear 0xygen sensor.

It listed a number of possible causes in my shop manual - everything from a bad sensor to an intake or injector leak. The car runs fine, so I'm betting the sensor is bad.

Does anyone have recent experience with O2 sensor replacement? What's the best source for a quality part? Should I go ahead and replace both of the sensors, even though 77 indicates a rear sensor failure?

TIA

 

Your Maxima engine is OBD-2 compliant. All Diagnostic Trouble Codes are four digits, with the first is always 0 or 1. Therefore your "77" is actually "0707" which points to the rear Oxygen Sensor.

Your Maxima has three Oxygen Sensors. Two are front sensors, mounted in
the Y-pipe between the exhaust manifolds and the Catalytic Converter. One
is a rear sensor, mounted in the exhaust pipe downstream of the Cat.

When both front Oxygen Sensors are operating normally the rear sensor serves only to keep tabs on the Catalytic Converter. That's the reason your engine is running well. The Engine Control Module (the computer) is not using the signal from the rear sensor to control engine management functions.

For more information about Oxygen Sensors go to
http://www.volksparts.com/o2sensors.htm

For specific information about replacing Oxygen Sensors on your Maxima see
the Chilton manual (page 4-13) or the Haynes manual (page 6-14).

In a different thread SprintMax said he got a great price on a replacement factory Oxygen Sensor from Vester Nissan. He didn't give a location or contact information. Perhaps he was referring to Vester Nissan of Clinton NC, 1-800-572-2005.

 

Thanks. I couldn't have asked for a more comprehensive explanation. I do have a Chilton's manual - but it was not clear on the fact that I have 3 sensors - not 2. I assumed 'rear' indicated the sensor for the rear bank. And as I said, Chilton's really didn't specify.

I've replaced O2 sensors on other cars before and it seems to be a pretty straightforward job, much like replacing a spark plug.

Thanks again for the information.

 

Hi Glen,

I noticed you listed your car as a '95 SE. There was an engine sensor recall for that year (maybe '96 as well), because the light would go on when nothing was wrong. It was a couple of years ago, but I remember it having to do with the oxygen sensor. The failure happened to my '95, I brought it in to a Nissan dealer, and they fixed it with no problem. You don't have to be under warranty to get this corrected.

Regards,
Gary