Fuse 41 - Oxygen Sensor Circuit

[PattyJoe]

Good Afternoon all,

Recently my 2002 Ford Explorer 4.0 completely shut off on me while driving. It would not even crank despite the battery being full. I paid to get it towed home only to find it was a blown fuse number 41 under the hood. I changed the fuse and it started right up. I drove it again to replicate the problem. Under the same conditions the fuse blew again. These conditions are as follows:
I had been driving for about 20 minutes before the fuse blew.
I was turning sharply into a driveway or onto a street both times when the fuse blew.
I was applying the brakes both times when the fuse blew.

After investigating online I have discovered the circuit that fuse 41 protects is for the oxygen sensors, the pcm relay, and a few vacuum components. I read that it is a common problem for the oxygen sensor wires to rub and/or melt so I checked them. They all appear to be intact and protected by the original shielding. I ran my trouble codes today. I have a P0141 and P0161. I purchased a Haynes manual and found both of these are 02 sensor trouble codes.

P0141 - 02 sensor heater circuit malfunction (bank 1, sensor 2)
P0161 - 02 sensor heater circuit malfunction (bank 2, sensor 2)

My questions are as follows:
Would bad 02 sensors cause this fuse (fuse 41 under hood) to blow?
Is it common for both of these 02 sensors to go bad at the same time?
Which oxygen sensors are they? There is conflicting information on the internet.

Thank you in advance for any information on the subject.

 

[imp]

P0141 - 02 sensor heater circuit malfunction (bank 1, sensor 2)
P0161 - 02 sensor heater circuit malfunction (bank 2, sensor 2)

OK, first, no matter what is said on the 'Net, Ford calls Right Bank (passenger side) "BANK 1". Therefore, "BANK 2" is the L.H., or driver side bank.

There are two O2 sensors per bank, one in front of the cat converters, and one behind them. The fronts, closest to the engine are called "POSITION 1"; heading back beyond the cats, those are called "POSITION 2". Thus "bank 1 sensor 2" means Right bank, after cat. "bank 2 sensor 2" means Left bank, after cat.

My questions are as follows:
Would bad 02 sensors cause this fuse (fuse 41 under hood) to blow? Yes, they could. Fuse 41 feeds the heater element in all 4 O2 sensors. A short circuit anywhere between the fuse and the sensors, or a short-circuited heater in one of the sensors, would blow that fuse. And, it could be an intermittent short, as caused by moving wires with frayed insulation bouncing against a grounded surface.
Is it common for both of these 02 sensors to go bad at the same time? Not only uncommon, but danged near impossible. But keep in mind those particular codes are used to alert to several different problems, for example, on my 2004, I keep getting heater codes, but never a fuse failure, because the cats are too old and inefficient. In your case, the failed fuse "kills" the PCM Power Relay too, which keeps the engine from running at all.
Which oxygen sensors are they? There is conflicting information on the internet. See above explanation. Be aware that Ford wiring diagrams, for brevity, list each O2 sensor as 11, 12, 21, and 22, using the nomenclature above, leaving out "bank" and "sensor" or "location".

If push comes to shove, and no evidence of the cause for the fuse blowing is found, a Dealership will change out entire wiring harnesses, LOTS of $$$. I would replace the wires feeding from the fuse to all 4 O2 sensors, having clipped off and abandoned the wires in the harness.

Thank you in advance for any information on the subject.

@PattyJoe Yer welcome! imp