I have seen a few issues with the lean code caused by a blown up intake gasket leaking oil out the back which then causes the oil to leak on the oxygen sensor.

take a look at the intake gasket, if its concave instead of convex then its kinda bad. the pressure got too high from a bad pcv separator and blew up the gasket.


On higher mileage discos I have seen that code from a slight leak at the flange caused by a bad weld on the catalytic converter.

 

I don't see how anyone can get two hands on it. I can barely get one arm up in there. Anyway got it apart. Dont' seem to be as dirty as I thought, clean inside. Should I focus my attention to a bad sensor? How and what kind of wrench to back it out?

 

Disconnect it while its cold. sometimes you can get it a bit easier from the top by squeezing your hand behind the block, but first you have to pull off the connector from the bracket and then you can pull off the connector from the oxygen sensor.

 

Decreased it,let it dry,put back together,erased code. Then went for drive, service light came back on after about 5 miles. Went back home, throwing code p0130 o2s CKT malfunction. Where to start MAF or o2s?

 

Does the scan tool you have allow you to read live data?

 

Yes it does, but dont know much about it. What should I look for?

 

Check the voltages both front O2 sensors are reporting. I have a feeling it is going to be a bad O2 sensor, due to the oil contamination (which, by the way, have you checked to see where the oil is coming from?), but I would like to know what both front sensors are showing on the scan tool, so other members can see, and correct me if I'm wrong.

 

Both front sensors look to be about the same.Ln-rich.means0.445 min0.395 max0.995

 

lordmorpheus? someone?

 

I am stumped. I have been thinking of this off and on since you posted that both front sensors appear to be reading the same, and truthfully, have been hoping that someone else might give some insight.

I am not a trained technician. Everything I think I know has come from personal experiences, and learning from others, and from thinking things through.

You said the sensor had oil on it, but the contacts appeared clean. Is it possible that oil got onto the backside of the connection, and between the wires and the terminals? If I had to gamble, or I were having the same problem, I would replace the O2 sensor, as it is far cheaper than the MAF, and I would think the MAF would single out one bank.

Have you ruled out an air leak on that bank? ...either on intake or exhaust, though I would think that would cause that O2 to read differently than the other bank...

You might pull both front sensors, and compare. Soak down with PB blaster the day before, and you can either get an O2 sensor socket, or use an open end wrench. If the sensor in question is much more carboned up, I would definitely look closer towards something prior to the sensor.