Repairing rodent damage to my F250 wiring harness
My F250 does not get driven much. Since it is primarily a tow vehicle, it spends most of its time parked in the woods with the trailers. This leaves it susceptible to rodent damage.
I got an oxygen sensor error code one day out of the blue. I began by testing the resistance of the heater circuit. It was in spec but on the high side. So I tracked down a Motorcraft sensor in the next town to the south and swapped it out.
The error code was still there. So I took a closer look at the wiring. That is when I noticed a chunk of insulation was missing right at the connector on the harness side.
This connector is located between the transmission and the cab floor above the catalytic converter. I can barely get one hand on it. So there was no way I was going to be able to solder the wires back together.
I debated on pulling the cab bit decided to remove the catalytic converters instead, I considered buying a new set since these are likely original but I decided to just be careful with mine after I saw the price.
Removing the cats required unbolting the flanges at each manifold and at the pipe leading to the muffler. The relatively new nuts on the driver side came off easily. One of the bolts at the tailpipe broke so I broke out the torch and removed the second one successfully.
One of the nuts on the passenger side came off after a bit of heat. The second nut simply rounded off when I tried to turn it. I tried several tricks to get it loose. I ended up using a hole saw and cutting the nut until it fell off.
Even with all the bolts lose getting the Y pipe out was no easy task. I had to loosen the hanger at the tailpipe and loosen the transmission to cross member bolts and lift the transmission slightly to get enough space to get the pipe out.
With the Cats out of the way, I could at least get two hands on the connector and harness. A closer inspection showed that the wire was broken too close to the connector to splice the original wire. The good news was only one wire was damaged,
I purchased a Dorman replacement connector.
Since only one wire was damaged I elected to extract a pin from the new connector and use it in the old connector. I left the other three wires in place. Extracting the pin required removing the red divider and then using a pin extractor tool to depress the plastic clip that holds the pin in place.
Performing the same trick on the harness in the truck was not quite as easy but I was eventually successful. I inserted the new pin and wire in the old connector and reassembled the connector. I stripped back a bit of the original wire and used a heat shrink butt connector to make the splice.
Then I reinstalled the converter and reconnected the wires. I then put the transmission back in place and reconnected the exhaust hangers. I then plugged back in all four O2 sensors.
On startup, the exhaust flanges all leaked a bit. I retightened them warm and they sealed a bit better. After a couple of heat cycles, they sealed back like they were before.
I cleared the codes and rescanned. No more check engine light and no pending codes.
