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Any mechanics or car experts here? O2 sensor heater circuit
Posted on 3/20/26 at 6:42 pm
Posted on 3/20/26 at 6:42 pm
I recently bought an '05 F-150 with the 4.2L engine and 5 speed m/t to take the burden off our family-sized vehicle since we drive 50k mi/yr. I bought this with the check engine light on showing P0141 and P0161 codes, one code for each downstream O2 sensor heater circuit. I thought it would be an easy fix but am having no luck.
I've changed out both downstream O2 sensors, MAF sensor, and fuse for the circuit. I'm also not seeing any damage to the wiring harness running to the sensors.
The remaining possible causes I've found online are exhaust leaks and/or bad cats. I'd think its weird that both catalytic converters are bad though.
Anyone experienced something similar who might have some suggestions?
I've changed out both downstream O2 sensors, MAF sensor, and fuse for the circuit. I'm also not seeing any damage to the wiring harness running to the sensors.
The remaining possible causes I've found online are exhaust leaks and/or bad cats. I'd think its weird that both catalytic converters are bad though.
Anyone experienced something similar who might have some suggestions?
19
Posted on 3/20/26 at 6:45 pm to ISEN_AG
Rodents done chewed a wire and you haven’t found it yet
ETA: I’m not a mechanic, or car expert. Or rodent expert
ETA: I’m not a mechanic, or car expert. Or rodent expert
This post was edited on 3/20/26 at 6:47 pm
Posted on 3/20/26 at 6:54 pm to SuperSaint
Clear the codes and drive it 100 miles or so and see if the codes come back on. I have an 08 Silverado and the 02 sensor codes come on and off all the time. I've changed them several times in the past. Now I just make sure they're cleared every year for inspection sticker passing.
Posted on 3/20/26 at 6:58 pm to ISEN_AG
Keep throwing parts at it, you’re bound to hit it sooner or later.
Posted on 3/20/26 at 7:01 pm to justjoe906
quote:
Now I just make sure they're cleared every year for inspection sticker passing.
Thats the bad part. Even though Texas got rid of annual inspections, I still live in an emissions testing county, so I've had this thing for almost 2 weeks and can't get it registered in my name yet.
I did clear the codes after changing both sensors but the faults came back immediately. Then I tried the MAF early this week and yesterday changed the fuse. So I've driven about 70 miles since changing the fuse.
The only way I've cleared the codes for longer is by unplugging the wires from the PCM, but even then, they only stay gone for around 30 miles.
Posted on 3/20/26 at 7:05 pm to ISEN_AG
The good news is that they don’t matter for the performance of your truck so you can drive it with no worries - it won’t pass emissions though.
It’s weird you are getting issues on both. Did you actually clear the codes correctly? They shouldn’t come immediately back and it should have taken a few drive cycles if they were bad.
Edit: I see your other post that it’s 30 miles before coming back on. Wiring issue or clogged cats would be my next guess.
It’s weird you are getting issues on both. Did you actually clear the codes correctly? They shouldn’t come immediately back and it should have taken a few drive cycles if they were bad.
Edit: I see your other post that it’s 30 miles before coming back on. Wiring issue or clogged cats would be my next guess.
This post was edited on 3/20/26 at 7:10 pm
Posted on 3/20/26 at 7:11 pm to BigBinBR
quote:
Did you actually clear the codes correctly?
I believe so, but maybe there's another way.
I have the Bluedriver OBD2 and hit the "Clear codes" button.
Bluedriver OBD2 Bluetooth
This post was edited on 3/20/26 at 7:13 pm
Posted on 3/20/26 at 7:11 pm to ISEN_AG
Remove the light bulb on the code display.
Posted on 3/20/26 at 7:13 pm to ISEN_AG
Buy some spark plug extenders and put them on your 02 sensors.
Posted on 3/20/26 at 7:13 pm to justjoe906
quote:
Clear the codes and drive it 100 miles or so and see if the codes come back on. I have an 08 Silverado and the 02 sensor codes come on and off all the time. I've changed them several times in the past. Now I just make sure they're cleared every year for inspection sticker passing.
This won’t work in Texas. Their machine checks to make sure they have been tripped (driven enough) to make sure people are not just clearing them.
Posted on 3/20/26 at 7:14 pm to ISEN_AG
I’m not a mechanic, and I’m not really an expert on mechanical stuff, but I have slept in a Holiday Inn Express. If it were my vehicle, I’d trade it in…
Posted on 3/20/26 at 7:46 pm to ISEN_AG
What did the guy you bought the trunk from say about the codes?
Posted on 3/20/26 at 8:05 pm to ISEN_AG
Ask your husband.
Posted on 3/20/26 at 8:24 pm to ISEN_AG
Disconnect your battery and do a full reset of your computer systems. Google it.
Posted on 3/20/26 at 8:25 pm to ISEN_AG
If it's throwing codes for both header down stream I bet it's bad cats. Is the check engine light blinking? May try to space the O2 sensors and see if that helps. I have a car that had a cat code and I tried everything. Even a gallon of toluene in the gas. Ended up putting a header and a hi flow cat on it. Turned out one of the 2 banks of catalyst had broken loose.
You can get a Bluetooth obd reader $10-20 Amazon and the Torque app (free) and see live the O2 sensors values.
You can get a Bluetooth obd reader $10-20 Amazon and the Torque app (free) and see live the O2 sensors values.
Posted on 3/20/26 at 8:34 pm to UptownJoeBrown
quote:
What did the guy you bought the trunk from say about the codes?
Just, "Oh, O2 sensors, I've changed those out before. It's not bad."
Posted on 3/20/26 at 8:35 pm to soccerfüt
quote:
Ask your husband.
K.
Posted on 3/20/26 at 8:40 pm to ISEN_AG
First guess is bad cats from running rich too long.
Posted on 3/20/26 at 8:40 pm to ISEN_AG
Bad cats. Common
Posted on 3/20/26 at 8:58 pm to ISEN_AG
In this order:
Inspect for damage
Reference the O2 sensor and make sure it's the correct one. People box swap them and return them to parts stores.
If you wired in a universal sensor, triple check the wiring.
Verify voltage on the heater circuit
Test pre/post cat temps with an IR temp gun
If your scanner has the capabilities, read your LT and ST fuel trims and live data from the o2 sensors.
Test vacuum readings
Test back pressure
Inspect for damage
Reference the O2 sensor and make sure it's the correct one. People box swap them and return them to parts stores.
If you wired in a universal sensor, triple check the wiring.
Verify voltage on the heater circuit
Test pre/post cat temps with an IR temp gun
If your scanner has the capabilities, read your LT and ST fuel trims and live data from the o2 sensors.
Test vacuum readings
Test back pressure
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