I have 16540 - Oxygen (Lambda) Sensor B2 S2: Malfunction in Circuit
P0156 - 92-00 - Unknown Error Elaboration


I was told it points towards the driver side post-cat O2 sensor.


When I had the transmission out, I did NOT mark which downstream O2 is right or left. Tracing the wires from under the car, over the trans into the engine bay to the connectors is very difficult.


Any suggestions how to determine which one is which?
The sensors themselves and the connectors are easy to get to. Could I use an Ohm meter and measure continuity from the connector to the sensor? Or put a 9V battery with negative to ground and positive to the outside of the sensor, then look for 9V on the connector pins to ground?


Any suggestions?

 

Ohm it out - it's the quickest and easiest way. You have one black, one white, and two brown wires. Go from a black or white wire on the connector of your choice, and probe that color wire on each sensor so you can identify which side is which.

 

IIRC, the wires on the sensor end are sealed and not accessible with a probe.
But the housing should be grounded, and one of the connectors should be ground, too?

 

Good point. The two brown wires are the heaters, white I believe is the signal, and black is the ground. Easy enough to verify by probing wire to case as you suggested, but yes I believe you're correct.

 

Good point. The two brown wires are the heaters, white I believe is the signal, and black is the ground. Easy enough to verify by probing wire to case as you suggested, but yes I believe you're correct.

 

Will try Ohming the sensor case to connector; easy enough.

 

Until a couple of weeks ago, I had the code:
16540 - Oxygen (Lambda) Sensor B2 S2: Malfunction in Circuit
P0156 - 95-00 - Unknown Error Elaboration

Changed the driver side, upper (pre cat) O2 sensor. Code gone.

After timing belt change, now have:

16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 92-00 - Unknown Error Elaboration

If "B" points towards 'bank', then this would mean that now the other (post cat) O2 on the driver side is acting up.

What is going on here?
Could it be that the sensor is just a bit 'miffed' from stuff done on the engine over the last 4 days?

 

FRONT

Driver / Passenger
LEFT | RIGHT
B2S1 | B1S1 (pre cat, upper, front)
CAT | CAT
B2S2 | B1S2 (post cat, lower, rear)

BACK

I don't know what I was thinking (obviously nothing) when changing sensors to get rid of the B2S2 code !!!
Instead of the POST cat, I installed a new sensor that I had (4 wire) in the PRE cat location.

Now that this one throws a code, I suspect that my 4 wire needs some more tinkering. I read the 4th wire is ground (empty position in the ECU connector). Do I need to connect that wire to a ground? Maybe that kills the code?

Since I did NOT address the older B2S2 code (and not coming up (yet?), likely because only idle running for several 10 min warmups so far), it likely will show up again later.

Can I use the likely good B2S1 I replaced in error for the B2S2 post cat location?

 

The old upper/precat sensor was 3 wire (2 white, 1 black).

According to the Bosch chart below, that would make it a "D" type (Signal black, heaters (2) white).

In 4 wire version, the additional grey wire would be ground (which I currently have not connected, the pin in the ECU harness is blank). Should I run that to ground to get the 4 wire working?