P0161 despite O2 sensor replacement

MAHTYMAHT

MEMBER
2007 FORD ESCAPE
3.0L
V6
4WD
AUTOMATIC
90,000 MILES

Went to a local shop for state inspection, they discovered an exhaust leak and replaced a pipe. Bolts were stripped in the process, A/C compressor had to be removed to repair it. They called to say they were done and I got a check engine light when I left, P0161. I went back and they replaced the B2S2 just to see, no joy. If I had the PCM pinout, I'd test the heater circuit wires, or just lay new ones. Where might I find the pinout for that thing?

2 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

I attached the wiring diagram for the O2 sensor. There is a fuse for the heater circuit. I circled it and check for power on both sides.

Roy

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Tuesday, March 17th, 2020 AT 7:25 AM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

Okay, so the breakdown on O2 sensors is O2S11 and O2S21 are the O2 sensors the PCM uses to maintain the air:fuel ratio at 14.7:1 to keep your engine running at stoichmetric, or perfect burning for an internal combustion engine. O2 sensors O2S12 and O2S22 are the O2 sensors that read the effiency of the catalytic converters and do nothing else. For vehicle performance O2S11 and O2S21 are the O2 sensors that count. Having said that, I have included for you in the diagrams down below the possible causes for DTC P0161, the engine management wiring diagrams with the O2 sensor heater wires highlighted for you, and lastly the pinout diagrams for all 4 O2 sensors. Please go through these guides and get back to us with what you find out. Also, if any splicing to the O2 sensor circuits is to be done, it must be done on the vehicle wiring harness side. If you cut into any of the O2 sensor wires then the O2 sensor is ruined and will need to be replaced. I hope this helps.

Thanks,
Alex
2CarPros

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