I have a 99 F150 with a 4.2L V-6. The problem is a code P0156 bank 2 sensor 2. I was told that that was the O2 sensor after the cat on the right side was bad. So I changed it. The code came back. Since then I have found out that the second bank should be on the left side. However, I have single exhaust on my truck. Can someone tell me where this sensor is located? Or do I have a wiring problem? Any help would be greatly appreciated. I have to get an inspection sticker on this thing and can't until I get that light to go out!

 

you reset the computer?

 

Bank 2 is the driver's side. The downstream sensor or Sensor 2 is the sensor just behind the cat, about even with the tailshaft of the transmission. Two exhaust manifolds, two cats one behind each manifold, then a crossover pipe just behind the transmission, then a single exhaust. Sensor 2 sensors are just behind each cat, just before the crossover pipe.

If it is the O2 sensor and you still have the old sensor, you can swap the new one and put the old one back in. Or at least swap the current two and see if the problem follows.

As usual, the Ford pinpoint tests for this were useless as **** on a boar shoat. Gist is 'Watch scan tool while wiggling bending and shaking small sections of the Electronic Engine Control harness from PCM to HO2S'. They think it's a wiring thing. However, then they say if it's still bad, replace the HO2S.

There is better info in 'emissions control/drivability'. They list possible P0156 causes as (1) Blown fuse, (2) Short to VPWR in harness or HO2S, (3) Water in harness, (4) Open VPWR or GND circuit, (5) Low Battery Voltage, (6) Poor electrical connections from PCM to HO2S sensor, (4) HO2S heater, (5) PCM. The heater draws enough amps, I'm surpised there wasn't a relay in there somewhere, that's a lot for a PCM driver to ground.