2003 Explorer 4.6L oxygen sensor circuit problems | Ford Explorer Forums - Serious Explorations

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2003 Explorer 4.6L oxygen sensor circuit problems


New Member
March 26, 2023
Reaction score
City, State
Shady Cove
Year, Model & Trim Level
2003 Explorer XLT 4.6L
I recently picked up this 03 Explorer with the 4.6L in it, the odometer says roughly 198k. I bought it pretty cheap so I've been fixing things and sorting out the bugs. Up until now the fixing has all been mechanical, bearing assy's, upper control arms, latches, hinges, etc.

Here's the deal, check engine light was on when I got it and I don't remember the exact code it gave but I remember it was both upstream O2 sensors so I bought and replaced both. Prior to replacing them it seemed to run well enough while occasionally running a little rough for a few minutes while cold. Now that I've replaced both upstream O2 sensors it runs like absolute sh*t and has a pretty bad misfire and won't go down the road without popping and banging. I read that the common issues related to the O2 sensors are burned/chaffed wires and fuse #41. Checked the fuse, it was good. Checked the wires, both were good at least up to the connector from the sensor. The old sensors were NTK and didn't look to be that old, or even bad.

The codes I got last time I checked were as follows:
P2196 O2 Sensor Signal Stuck Lean - Bank #1, Sensor #1
P2198 O2 Sensor Signal Stuck Rich - Bank #2, Sensor #1
P0135 HO2SHTR11 Heater Circuit Error
P0053 HO2S11 Heater Resistance Beyond Limits
P0059 HO2S Heater Resistance - Bank 2 Sensor 1

After checking the fuse and looking at the wiring today I ran it again. It ran fine for the first 10-15 seconds and then ran like dog sh*t again. Then after about a minute it cleared up and ran perfect. I cleared the codes and then it started running like crap again. I checked the codes and now it is only giving me "P0135 HO2SHTR11 Heater Circuit Error", though I've only let it run for a couple minutes after clearing the codes so the rest might show up later.

Immediately after typing this I'm going to get in there and see what the wires look like from connector to harness but I'm not very hopeful because, as far as I could tell, the plastic wire loom was still intact after the electrical connector. This is supposed to be my daily so I NEED this to be fixed ASAP so anything you guys can give me that will help me get this going would be very much appreciated!

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Never mind. I found the issue. I pulled the bank 1 upstream sensor connector up into the engine bay to look at it better and found that all 4 wires were bare where they go into the connector and were shorting out there.

What do you use to replace the connector in such a situation, or do you just try to re-insulate the wires with liquid electric tape or something like that?


What do you use to replace the connector in such a situation, or do you just try to re-insulate the wires with liquid electric tape or something like that?

I'd just splice in a new connector

If the wire copper is still in good condition, what I would do is first clean that grime off of the area, then make a dam out of tape and fill with epoxy.

Mix up about 2 teaspoons of 5 minute epoxy, wrap a piece of clear packing tape around the perimeter of the connector, position the wires so they aren't shorting, and then pour the epoxy down into it and hold it till it sets up, then wait another few hours before installing it. The tape's adhesive would allow taking it off later without the epoxy permanently stuck to it, or you could just leave the tape on.

If it looks like the epoxy would seep down into the connector contacts area, then start only applying a tiny bit of epoxy to plug up the holes where the wires pass through, let that set up 10 minutes, then do the above.

If that doesn't work, time for a new connector. ;)

Maybe a pic would help illustrate...

epoxy dam.png