I was having CEL issues. The code indicated Bank 1 Sensor 2. I called AB, told them the issue, they sent out MHK500960. Said it was independent of side. (LR3 / Discovery 3 | '05 - '06 | RIGHT REAR)

Put it in the left side though. Never verified it was independent of the side or not. Just assumed based on our conversation.

Now it throws a code somewhere between 25-250 miles: P0137.

After install, I was having the P0171 Fuel Trim code through. The dealer updated the ECU and that was fixed. I wonder if I purchase the correct O2 sensor, I'll once again have P0171 thrown.

FYI - I am just realizing that the sensor sent to me specifically said Right Rear. The old one I replaced was MHK500910 (LH Rear).

 

Bank 1 is passenger side.

 

Well I'm dumb then!

 

No you are not, it's confusing.

 

I must have been looking at a D2 diagram or something.

On the passenger side, I was just out there, and the O2 sensor cable and connection was just hanging loose. Banging up against the transmission. I unplugged it and sure enough, 0.0 V to bank 1 sensor 2 (solves the bank 1 versus 2 "mystery").

Plugged it back in and voltage looks perfect. I guess I just try and see if I have another CEL and can diagnose it then.

Why would it randomly say low voltage - I wonder if that's a failure mode or a short from bouncing around?

 

Maybe the "hanging there" state was causing the connector to not be completely connected?

 

So I monitored the rear O2 sensor voltages during a long (>1 hr) drive yesterday. At first, both appear nominal: ~.7 V during normal operating conditions. Then, once things were warmed up, about 10-15 minutes in, the voltage on Bank 1 dropped to near zero for the remainder of the trip. It would sometimes fluctuate in the ~.1 V and below range, but mostly 0.0 V.

 

So now switch the rears and see if the phenomenon follows. That way you are sure it's a sensor.

 

Looks like it is fixed! Sequence I followed:

Bank 1 sensor 2 failure.
Replaced LH side with RH sensor. Same issue obviously.
Replaced RH side with old LH side (which was still working).
Looks good now!

The LH side is more difficult to change than the RH. Also, as far as I can tell, the only difference between the two are the support components for how they are secured.