Code 41c/42R: What's it really mean?
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,448
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From: CA Central Coast
Code 41c/42R: What's it really mean?
Question: Are the codes saying the voltage is high or out of range because it running lean/rich, or is it telling me that there is some other problem in the O2 sensor circuit?
I'm trying to diagnose the dreaded idle surge and running rich at all rpm's on my 93 F-150k 302 4x4. MAP, not MAF.
After CEL comes on it throws a KOEO code 41c "HEGO sensor out of range /always lean". KOER shows a 42R HEGO sensor voltage high/system rich...and believe me, it's RICH!
This before AND after a new O2 sensor, plugs, cap, rotor and IAC check/clean. I know I have other sensors and vac leak and BS to check, but the code baffles me: Is it saying the voltage is high or out of range because it running lean/rich, or is it telling me that there is some other problem in the O2 sensor circuit? I checked the fuse for it, it's ok.
I'm trying to diagnose the dreaded idle surge and running rich at all rpm's on my 93 F-150k 302 4x4. MAP, not MAF.
After CEL comes on it throws a KOEO code 41c "HEGO sensor out of range /always lean". KOER shows a 42R HEGO sensor voltage high/system rich...and believe me, it's RICH!
This before AND after a new O2 sensor, plugs, cap, rotor and IAC check/clean. I know I have other sensors and vac leak and BS to check, but the code baffles me: Is it saying the voltage is high or out of range because it running lean/rich, or is it telling me that there is some other problem in the O2 sensor circuit? I checked the fuse for it, it's ok.
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
The fault codes are the result of the other problems.
Fix the vacuum leak first. It's not a BS problem, it's probably the root of your rich mixture and the surging idle.
With a vacuum leak, the PCM cannot properly balance the mixture which leads to all your symptoms.
Steve
Fix the vacuum leak first. It's not a BS problem, it's probably the root of your rich mixture and the surging idle.
With a vacuum leak, the PCM cannot properly balance the mixture which leads to all your symptoms.
Steve
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,448
Likes: 2
From: CA Central Coast
Thanks...I wasn't using BS to mean unimportant, more like aaargh I don't have time for this.
I'm gonna throw a coolant temp sensor at it first, then chase vacuum if that doesn't work.
I'm gonna throw a coolant temp sensor at it first, then chase vacuum if that doesn't work.
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,448
Likes: 2
From: CA Central Coast
On the 86-97 Forum (and on the advice of a couple mechanics) The ECT has been implicated as a culprit. IF it's failed, it could be sending the wrong signal and telling the computer that the engine is cold, and needs more fuel. So I'm told. (Note: it didn't help).
That there might be a vacuum leak is also educated guessing at this point. I guess I was unclear in the OP. I'll start testing for vac leaks now that I finally located my vac gauge.
That there might be a vacuum leak is also educated guessing at this point. I guess I was unclear in the OP. I'll start testing for vac leaks now that I finally located my vac gauge.
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Fleet Mechanic
Joined: Feb 2004
Posts: 1,448
Likes: 2
From: CA Central Coast
Fixed it! It was the fuel pressure regulator, the fuel pressure was up to 80lbs instead of 35, overpowering the injectors.
Of course, after spending $70 at Napa and an hour cussing at it while fiddling, I find out it (the FPR) is a recall item on my truck, and Ford would've done the job for free. BUt at least she's purring again.
Of course, after spending $70 at Napa and an hour cussing at it while fiddling, I find out it (the FPR) is a recall item on my truck, and Ford would've done the job for free. BUt at least she's purring again.
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