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Old 10-04-2022, 02:01 PM   #1
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Ford F53 O2 Sensor mystery

Short question: Can anyone share a wiring diagram for the O2 sensor 4 wire to PCM? 2013 Ford F53 motorhome (Forest River Georgetown)

More info...
I have a few trouble codes that threw the mechanice for a loop and he was almost settling on replacing the PCM/ECU (whatever you call the computer).


I tried swapping the O2 sensor, then took it to a mechanice and he put a new on on, I tried cleaning the MAF sensor and still get the code after 20 miles or so.

I checked the voltage of the black to brown wire on the O2 sensor harness while the truck was running and I was expecting it to read 2-5v consistently but instead it jumps around between 0, 1, 2 volts for a min or so then no voltage (for the few minutes i had it monitoring).

QUESTIONS:
-Is that voltage activity normal?
-Any ideas?

My next step was to test continuity on the wire as it enters the PCM and if thats good replace the PCM???

Thanks in advance!!!



P2270 - O2 Sensor Signal Stuck Lean Bank 1 Sensor 2
P2098 - Post Catalyst Fuel Trim System Too Lean Bank 2
P2270 - 02 Sensor Signal Stuck Lean Bank 1 Sensor 2 (Duplicate but shows twice when i clear the codes).
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Old 10-06-2022, 10:05 AM   #2
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MAF supplies both bank 1 and bank 2 so if it was maf issue would be on both banks. Best is to get a good scan tool and run forscan and watch short term and long term fuel trims. O2 sensors are not constant voltage , they go up and down and the pcm determines the average. DTC'S indicating lean means pcm has reached its calibrated maximum to add fuel to get the o2 to desired level. The pcm reads the signal from the o2, if there was a wire issue it would also set a code for short to ground or open.
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Old 10-06-2022, 10:30 AM   #3
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O2 sensor lean codes can also be caused by a vacuum leak leaning out the mixture.
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Old 10-06-2022, 10:41 AM   #4
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Quote:
Originally Posted by steve52 View Post
O2 sensor lean codes can also be caused by a vacuum leak leaning out the mixture.
This ^^^^^

There might be a vacuum leak on the intake on the bank 2 side of the engine. I think thatís the driver side cylinders.
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Old 10-07-2022, 06:42 AM   #5
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Quote:
Originally Posted by steve52 View Post
O2 sensor lean codes can also be caused by a vacuum leak leaning out the mixture.
Thank you Steve!
My thought was a vacuum leak would throw a code at the upstream sensor (one before the Cat). I was thinking vacuum leak between the headers and where the single Catalytic converter connects at the Y, but I was under the impression that point there would be enough pressure it wouldnt suck in air, (also visibly it looks good there).

*Full disclosure*
I know enough to be dangerous (learning a lot and not afraid to dig in) so question everything I am saying.


Thank you again for taking the time!
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Old 10-07-2022, 06:45 AM   #6
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Quote:
Originally Posted by SergioP View Post
This ^^^^^

There might be a vacuum leak on the intake on the bank 2 side of the engine. I think thatís the driver side cylinders.
Thank you Sergio!! Not sure if you saw my other post about the leak (I would think i would get an upstream O2 sensor code).

Also, great point on the side, visibly have inspected vacuum and they 'look' clean and tight... Any tips for checking for vacuum leak (I have googled of course, but nice hearing from a real person).

If the code is from downstream would it be isolated to one side?
Thanks again!!!
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Old 10-07-2022, 06:51 AM   #7
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Quote:
Originally Posted by avfordguy View Post
MAF supplies both bank 1 and bank 2 so if it was maf issue would be on both banks. Best is to get a good scan tool and run forscan and watch short term and long term fuel trims. O2 sensors are not constant voltage , they go up and down and the pcm determines the average. DTC'S indicating lean means pcm has reached its calibrated maximum to add fuel to get the o2 to desired level. The pcm reads the signal from the o2, if there was a wire issue it would also set a code for short to ground or open.
Thanks AV!
I have cleaned the MAF, but I was learning if MAF, the upstream sensors would be alerting and I just have the downstream ones (I think).

I have a cheap scan tool, but bought a better one should be here tom and I do have FORSCAN so I will try that later today - didnt know FORSCAN could do real time monitoring, but will check it out.

One interesting thing - yesterday with the ignition off, I ohm'd the four wire harness to ground and couldnt consistently get good ground? Is that normal? I was thinking one of the wires would go to ground. I did get a flash/beep briefly on one but regardless of what i did after i couldnt get that pin to test clean to ground again consistently.

I did get a diagram for the 4 wires to PCM but it is tight under that hood and the PCM wires are bundled up so worried i will do more damage if i start pulling the plugs out to test the wiring is good to the PCM... May be the next step for someone more qualified than me...

**I know enough to be dangerous here so question everything i say... LOL.

Thanks again!!!
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Old 10-07-2022, 07:22 AM   #8
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I was able to find a diagram of the 4 wire to the PCM.

Trying to determine how to test...

1 - Which wire would I test to ground none??
2 - Test continuity below
- Test Gray/Red ( on universal harness Gray) -> 26 on PCM
- Test Red/Light Gray (Black) -> 30 on PCM
- Test White Black (one of the white) -> 48 on PCM

*Hard to get a good read on the wires in the PCM without damaging the harness...

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