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O2 Sensor Rewire Help

JustTodd

New CEG'er
Joined
Aug 27, 2019
Messages
22
Location
Easley, SC
I've chased O2 wiring issues most of the time I've owned this car (Spring, 2017). The PO had similar problems with no real success. Huge shout out to the FoMoCo cost engineers, btw.

I don't remember the exact codes, but codes were showing for 3/4 O2 sensors, and the P0420 or 0430. Fortunately, my new job (at the time) teaching at a high school career campus with an automotive program paid dividends. The heater wires' insulation had ghosted and was shorting. My car became a class project. Student labor with electrical tape was a cheap and effective fix. I enjoyed driving the car CEL-free and picked up a solid 10% gain in MPG.

Of course, after about 1.5 years, the light returned. In the interim, I changed jobs as my program was cut, effectively losing access to cheap and effective troubleshooting and repair. So, I took the car to a local, trusted shop after relocating. Their diagnosis was similar: bad wiring from the car to the sensors. This was about a year ago and I don't remember the specific codes.

Going on 2 weeks ago, after catching up on maintenance on my caravan of clunkers, I finally dug out my scan tool. I was surprised to see 10 codes confirmed. I cleared them, drove the car about 5 miles, and the P0401 and P1151 returned. I've since fixed the ERG/0401, cleared codes, and was greeted by the P0153, P0420, and P0430.

After clearing them and driving about 150 consecutive miles, the catalyst codes stayed away. However, the 1151/0153 remained. The connector for B2S1 was a bit of a mess from the students' use of liquid electrical tape. However, it was easy enough to see bare copper from the car side wires. I attempted to cut out the connector and splice the wires directly to the sensor wires but noted the degradation of the wires and insulation. I made the best connections possible, especially given virtually not even a half inch of extra wire from the harness. No dice. Live data showed no change from the previously dead sensor with OEM wiring.

Keep in mind this sensor works great when cold. But when coolant gets close to 200 degrees, it seems to die and stick at around .020 volts. B2S2 actually looks pretty good when S1 decides to work and stays around .5 volts.

B1S1 also seems to work well. However, B1S2 mirrors S1, not quite a step behind it.

The connectors for all are similar to B2S1.

Oh, and today the CEL was off for the first 50 or so miles of my trip. My old friends P1151 and P0420 returned with no real surprise.

So, how feasible is completely rewiring all 4 sensors? And how time consuming? I'd prefer to bypass all (or most) of the original wiring. Does anyone have better diagrams than Haynes? So it appears the heater circuit wires go to the under hood fuse box and the sensor wires directly to the PCM? Any tips or tricks? Anyone done this?
 
That .75 BN line that goes through S48 and S53 is the constant voltage power supply from the PCM to most of the sensors on the drivetrain. It goes through a bunch of drawings so its not practical to post them all. I would say if you aren't having trouble with everything else on the car, then that line is probably okay.
 
As far as feasability of replacing all that wiring...I wouldnt think it would be terribly difficult with the exception of the constant voltage power supply.
You have to decide if your going to try to de-pin and re-pin the connectors or just splice wires in, but the routing is pretty straightforward.
 
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