1995 Nissan Altima Knock Sensor AND Rear Ox Sensor heat trouble codes

Question

My mother-in-law has a 1995 Nissan Altima, four cyl. Check engine light codes are 34 and 77 (34 = knock sensor circuit / 77 = rear oxygen sensor heat circuit). I have the Childris manual but I can't find these items in the book. I can locate the knock sensor on the 240SX engine (wrong engine) but not on the Altima. I'm thinking that a problem with the knock sensor may be causing an additional problem to show up as the rear ox sensor heat.

To start, I want to locate the Knock Sensor, but can't locate it. I also can't locate the "Rear Ox Sensor Heat Circuit" either. I'm sure it's somewhere easy, but I don't want to start chasing the wrong thing.

Please Help.

Thanks.

Answer 1

The knock sensor will not cause the check engine light to come on and will not cause the engine to run bad. But if you want to replace it, it is on the right side (side closest to the fire wall) under the exhaust manifold and is mounted to the engine block. You can only get to it from under the vehicle and is held in by one bolt the goes through the middle of it and is round in shape with a connector going to it. The rear O2 (oxygen sensor) is located on the exhaust just after the catalytic converter.

Knock sensor part number 2206030P00 and costs about $172

Rear O2 sensor part number 226A040U62 and costs about $175

These are Nissan factory part numbers. Prices may very depending on dealer.