SOLVED: Code 41 O2 sensor issue.

[A4LD_Nghtme]

Hey there.
I just started getting a check engine light and the only code I'm pulling is code 41. This is a newer o2 sensor and I have a replacement but was wondering what else could be the issue. I bench tested the grey and black wires and received rising and lowering voltage when using a torch on the end which I assume means those wires are good but I can't be to sure as I read 41 mean 3 things, 41 R HEGO (HO2S) sensor voltage low / system lean
41 C HEGO (HO2S) sensor signal out of range / always lean
41 C No HO2S switching detected

Any ideas how to fix this up right?

 

[rusty ol ranger]

Lean reading on the O2 could possibly be not the O2 itself...a vaccum leak, exhaust leak (before O2) can trick the O2 into thinking its lean.

Hows it running?

 

[A4LD_Nghtme]

Lean reading on the O2 could possibly be not the O2 itself...a vaccum leak, exhaust leak (before O2) can trick the O2 into thinking its lean.

Hows it running?

It seems bogged down like it's lost some power otherwise everything seems in order.

 

[rusty ol ranger]

It seems bogged down like it's lost some power otherwise everything seems in order.

Start looking for vaccum leaks

 

[A4LD_Nghtme]

Start looking for vaccum leaks

Everything is connected. Where should I test and how? I don't have much brake cleaner to test. I can replace the o2 sensor and disconnect and reconnect all fittings

 

[rusty ol ranger]

Everything is connected. Where should I test and how? I don't have much brake cleaner to test. I can replace the o2 sensor and disconnect and reconnect all fittings

Use starting fluid and spray around espicially where the upper intake bolts to the lower. While its idleing and listen for idle changes

I wouldnt mess with the O2 anymore untill you check for vacuum leakes

 

[A4LD_Nghtme]

Alright I sprayed fluid at the throttle body, the three lines under the throttle body, the vac line to air filter and the cap, the intake manifold, injectors, and the 4 lines that lead to the brake booster/climate res/fpr and I did not notice a difference in idle or engine sound. Still getting KOER 41

 

[rusty ol ranger]

@RonD

 

[RonD]

41 (R) System lean

Is the engine pinging/knocking when accelerating?
And/Or overheating
These mean its "actually" running Lean

Lean codes don't usually mean the engine is actually running Lean, they are set when computer's OPEN TIME calculations for injectors are not long enough.......according to O2 feedback
So computer is opening injectors longer to compensate, and it reports this as Code 41

O2s only "see" the oxygen that's in the exhaust, there is a narrow range of oxygen content, the computer adds more or less fuel(longer and shorter injector open times) to try and keep the O2 in that range
O2s use 0.1volt to 0.9volt range
0.1v is high oxygen(Lean)
0.9v is low oxygen(Rich)
Computer tries to keep O2 voltage at 0.4v

So "low O2 voltage" = Lean, 41 can be defined as low O2 voltage or just Lean, same thing

Yes, vacuum leak means Unreported air is coming in that computer doesn't know about, so it has to add more fuel than it calculated, so longer open time for injectors and Lean code

Low fuel pressure
There is no fuel pressure sensor, computer bases its Open Time calculations on 35psi and each injector
If there is only 20psi, then computer has to open injectors longer, so Lean code

Misfires
When a cylinder fires it burns up fuel AND Oxygen
When it misfires no oxygen is burn and its dumper in to exhaust where O2 sees that extra oxygen............

Exhaust manifold leak
Exhaust leaks also SUCK IN air, O2s would see that extra oxygen, so Lean
But leak has to be between engine and O2, muffler leaks wouldn't do that, lol

Exhaust leak or misfires would also cause MPG to go into the toilet because they are "false" leans

Adding more fuel because there is a vacuum leak or low fuel pressure wouldn't change MPG

 

[A4LD_Nghtme]

41 (R) System lean

Is the engine pinging/knocking when accelerating?
And/Or overheating
These mean its "actually" running Lean

Lean codes don't usually mean the engine is actually running Lean, they are set when computer's OPEN TIME calculations for injectors are not long enough.......according to O2 feedback
So computer is opening injectors longer to compensate, and it reports this as Code 41

O2s only "see" the oxygen that's in the exhaust, there is a narrow range of oxygen content, the computer adds more or less fuel(longer and shorter injector open times) to try and keep the O2 in that range
O2s use 0.1volt to 0.9volt range
0.1v is high oxygen(Lean)
0.9v is low oxygen(Rich)
Computer tries to keep O2 voltage at 0.4v

So "low O2 voltage" = Lean, 41 can be defined as low O2 voltage or just Lean, same thing

Yes, vacuum leak means Unreported air is coming in that computer doesn't know about, so it has to add more fuel than it calculated, so longer open time for injectors and Lean code

Low fuel pressure
There is no fuel pressure sensor, computer bases its Open Time calculations on 35psi and each injector
If there is only 20psi, then computer has to open injectors longer, so Lean code

Misfires
When a cylinder fires it burns up fuel AND Oxygen
When it misfires no oxygen is burn and its dumper in to exhaust where O2 sees that extra oxygen............

Exhaust manifold leak
Exhaust leaks also SUCK IN air, O2s would see that extra oxygen, so Lean
But leak has to be between engine and O2, muffler leaks wouldn't do that, lol

Exhaust leak or misfires would also cause MPG to go into the toilet because they are "false" leans

Adding more fuel because there is a vacuum leak or low fuel pressure wouldn't change MPG

I'll pull spark wires tomorrow to check for misfire, I'll test fuel pressure, check fpr vac line for fuel, clean my maf and air filter, I'll recheck timing, recheck for vaccum leaks, possibly pull sparks to check for fowling and possibly pull injectors to see if they are clogged even though i installed new accels over a year ago.

Is there anything else I should check/perform to avoid taking this thing to a shop? I've heard 41 can be a real hair puller

 

[RonD]

You will feel a misfire if its bad enough to set a Lean code

FPR leak in diaphragm(vacuum) would cause Rich code, sucks raw fuel into intake, but test its vacuum hose

Check spark plug tips for darker color, that would mean a False Lean, engine is running Richer than it should

Test PCV valve, its a "controlled" vacuum leak, when they get oily they can stick open at idle, should be mostly closed

Also test Power Brake booster, hose, and then booster
Booster test, shut off engine, press brake pedal down 3 times, 4th time it should get hard to push
Then start engine, shut it off, wait 5min and do the same test
Booster should hold vacuum for a day to a month
A leaking booster is like a vacuum leak, because it is, lol

A clogged exhaust can cause Lean code as well but you would have more symptoms like slow REVing and lack of power at highway speeds

 

[r-hindl71]

While I was working as a Ford tech I offended found where the rubber elbow for the vacumn line to the pcv was brittle and had a hole in it You might to check there closely, that was the most common problem I found

 

[rusty ol ranger]

I would check for voltage down to the O2 sensor.

The no switching detected kinda seems like maybe the ECM isnt getting the signal...IE broken/bad wire.

Might even be the O2 itself.

 

[A4LD_Nghtme]

Alright so far I've cleaned the MAF, cleaned the air filter, checked for misfire, replaced power brake booster grommet and check valve, clamped a loose line to the speed control servo, regasketed the MAF housing cause the gasket was falling apart, checked torque on o2 sensor, checked torque on intake manifold and undid the jet 66110 monitor that installed just before getting CEL. Still no improvement. It runs great at first but then like to start stuttering at idle and loses power. Should I just take this thing to aamco

 

[RonD]

Pull the computer and open it up

Look for any corrosion, computer board is coated with a clear resin, on both sides, so should be clean
There will be some radial capacitors, 2 to 4, they look like a barrel standing on end, these do blow out, top will not be flat but bowed, or they will leak at the bottom
Easy to see
Easy to replace these, under $1 each

Have a look at the 60-wire connector pins and slots, for corrosion
Sometimes just unplugging and plugging back in ANY connector will clean its contacts