Check engine light codes lots of them

[zach7685]

Hey Guys, I'v had both check engine lights on in my pathfinders for years now. they have always been the o2 sensors. Today, I decided it would check them again for the fun of it and this is what I got:

On my red one: P1040, P0139, P0159, P0138, and P0158. some of them are the same thing i think.

On my white one: P0138 and P0505.
On my white one I had the idle air control valve replaced twice and re calibrated many more times. We think its the computer and the car runs fine, just stalls when you start it unless you give it gas. Any help is appreciated.

[atraudes]

First off, I'm assuming P1040 is actually P0140. The FSM doesn't make mention of P1040 anywhere, but P0140 is directly related to two of your other codes. Second, I'm not sure what you mean by red vs. white. I assumed the color of the unit you used to pull the codes?

P0138, P0139, and P0140 are all due to your Heated oxygen sensor 2 (Bank 1).

P0158 and P0159 are due to your Heated oxygen sensor 2 (Bank 2).

P0505 is the Idle Air Control Valve.

Stalling unless you step on the gas pedal after starting definitely sounds like an IACV problem. Since you've replaced the unit twice I'm suspecting a harness problem. There are some troubleshooting steps for this in the FSM at EC-426 in the 2001 Pathfinder/QX4 manual.

As for the oxygen sensors, I believe the ones that are having problems with are the ones after the catalytic converter (downstream). They're right in front of your face when you crawl under the car and look at the exhaust. Be warned: running the wires up to where they need to be plugged in is a bit challenging when you replace them. Also, I had some problems with the connectors being different when I replaced mine. That was resolved by splicing the old connectors onto the new wire.

The Bosch part finder will give you the model numbers of the sensors you need:

http://www.boschautoparts.com/vehiclepa ... inder.aspx

Let us know how it goes!

[atraudes]

It just occurred to me that red and white may be the colors of the vehicles lol

[zach7685]

Thanks for the links. And what kind of issue do you think the harness has?

[atraudes]

Any of the six wires that connect to the IACV could be shorted or not connecting. This could be caused by the insulation being melted off, getting cut or severed by rubbing against some sharp metal (or getting banged into while we're working on something else), or the wire breaking due to being old and being strained.