CEL - P0174 code

[StellarAuto]

I know it's not the easiest thing in the world to do but... Is it possible to swap O2's (B1,B2) and see if CEL changes to P0171 (lean B1)?

[JR-Vette]

Originally Posted by JANNETTYRACING

Great Detailed Information JR, Thanks for your time.

I never let my fuel trims get outside of + or - 4% so I didn't know where the Threshold was.

When I see the code on cars that come in the fuel trims are usually + or- 25%

Ted.

Many times a +25 ( that is the highest value PCM will report so it could even be higher) is from Ethanol in gas that sensors and PCM cannot react to.
If long terms are that high but short terms are not suspect a gas issue.
Reason GM and other nameplates refused to agree with the feds on the new E15 and GM says they cannot warranty for.
Worse for older cars like C5 Corvettes, Camaro, etc as PCM gets into a wacked state as no software in PCM can revert from a high +25% due to high ethanol percent and simple tests of gas by owners can assure what percent is really in their cars

Not the best example but good enough to see this Camaro putting out 550 HP ( boosted) you see almost no engine knock yet one side reporting as much as 20% lean and other side not as lean long term but short time fuel trims nuts on.

[Inferno Orange 2SS-RS]

What type of air filter do you have? Oiled filters that leak just a little oil on the MAF could also give off this code. I had this issue on my truck. I cleaned the MAF and went to an unoiled filter and had no more issues.

[caverman]

Ok....I'll try to take a look at the 02 sensor again.

My car has just over 9k so mileage isn't that bad. Headers are KOOKS brand so I hope there wouldn't be any leaks but you never know.

Again I'm more skeptical in my situation of something with the 02 since I went basically 6k with the header install/tune without issues. Then seeing this issue shortly after removal/reinstall of exhaust.

[Cam 427]

Originally Posted by StellarAuto

I know it's not the easiest thing in the world to do but... Is it possible to swap O2's (B1,B2) and see if CEL changes to P0171 (lean B1)?

+1

[JR-Vette]

Originally Posted by StellarAuto

I know it's not the easiest thing in the world to do but... Is it possible to swap O2's (B1,B2) and see if CEL changes to P0171 (lean B1)?

Yes if you mean the flip is with another front, same for rear but most cases fronts have a different connector shape then the rears and if so then a rear could not be swapped with a front.
So a BxS1 cannot be swapped with a BxS2

In any case if swapping position but best case is then to reset the PCM so all long term averages are erased and then you would see results of swap quickly and PCM would do new 02 tests.
Being tests are done on cold starts best to monitor then to see how all 4 02s are functioning as a weak or dirty may look OK once they are hot but are out of range when they are cold

[StellarAuto]

Yes. Swap B1S1 (Os sensor drivers side before cat.) with B2S1 (O2 sensor pass. side before cat.). Clear CEL and test drive for as long as it has taken for it to come on the past couple of times you cleared and got this same code. If P0174 re-occures, the O2 is not the culprit and replacing it would be a waste of money. If P0171 is shown, then it is definetly an O2 problem.

[caverman]

Ok....so here is an update. First off I thought my installer got rid of my rear cats with header install. Not the case though.....I still have both front and rear 02 sensors. Looking back on when the exhaust was taken out for my bushings it had to have been the rear 02 sensors that were hanging down since the front sensors are in the header collector and we didn't touch the headers. We only removed the exhaust from right after the headers.

However, based on the fact that the rear 02 sensors should have been tuned out with the tune for the headers I focused on the front 02 sensors. I was a little concerned since those sensors have never been taken off since the header install. For troubleshooting purposes though I decide to switch the driver side and passenger side front sensors.

After completely unplugging and swapping the two sensors, then zip tieing them out of the way.....started up the car and CEL instantly went away. I'm kinda shocked that the CEL cleared itself and did it immediately. I would've thought it would take a couple engine starts to run through the tests again. I've only driven it for 10 min from my dad's shop to my house but I started it at least 4 times after the sensor swap and no CEL. I'm keeping my fingers crossed it stays that way.

[bluetorp]

Originally Posted by caverman

After completely unplugging and swapping the two sensors, then zip tieing them out of the way.....started up the car and CEL instantly went away. I'm kinda shocked that the CEL cleared itself and did it immediately. I would've thought it would take a couple engine starts to run through the tests again. I've only driven it for 10 min from my dad's shop to my house but I started it at least 4 times after the sensor swap and no CEL. I'm keeping my fingers crossed it stays that way.

If the lean code is going to track with the sensor and show up on the bank that you swapped it into, it won't show up immediately. Rich/lean codes fire off when the LTFTs are over the +/- threshold, and it takes a bit of closed-loop operation for the STFTs to learn that much of a swing into the LTFTs. Also, LTFT learning is disabled under a certain coolant temp (can't say what it is off the top of my head, but it's above the temp threshold for closed-loop operation and closer to normal operating temp). Nothing to do with on/off cycles. You'll have to drive it around a bit to see if the code comes back, and if it tracks with the sensor swap.

[JANNETTYRACING]

Originally Posted by caverman

Ok....so here is an update. First off I thought my installer got rid of my rear cats with header install. Not the case though.....I still have both front and rear 02 sensors. Looking back on when the exhaust was taken out for my bushings it had to have been the rear 02 sensors that were hanging down since the front sensors are in the header collector and we didn't touch the headers. We only removed the exhaust from right after the headers.

However, based on the fact that the rear 02 sensors should have been tuned out with the tune for the headers I focused on the front 02 sensors. I was a little concerned since those sensors have never been taken off since the header install. For troubleshooting purposes though I decide to switch the driver side and passenger side front sensors.

After completely unplugging and swapping the two sensors, then zip tieing them out of the way.....started up the car and CEL instantly went away. I'm kinda shocked that the CEL cleared itself and did it immediately. I would've thought it would take a couple engine starts to run through the tests again. I've only driven it for 10 min from my dad's shop to my house but I started it at least 4 times after the sensor swap and no CEL. I'm keeping my fingers crossed it stays that way.

Did you actually scan for the code or did the light just go out coincidentally?

Ted.

[caverman]

Originally Posted by JANNETTYRACING

Did you actually scan for the code or did the light just go out coincidentally?

Ted.

Sorry Ted....I missed this question. After switching the two front O2 sensors the CEL went off automatically. I didn't clear them manually. The CEL eventually came back on a week or so later. I went back to AutoZone to scan it and it now said P0174 and P0171 were lean. It's possible that it might have said that before and I just missed the fact that it was reading two codes. So I cleared it again in hopes that if it came back on that it would say Bank 1 (initially it said Bank 2 before the switch) was lean.

Well, unfortunately a couple weeks later (which was last week) it came on again. This time it's saying both P0174 and P0171....bank 1 and bank 2 are too lean.

Wierd thing is that it came on last Thursday but didn't have time to go read it because I was going out of town Friday. I got back on Sunday (two days ago) and just got the chance to drive it today but my wife drove the car yesterday. I had to run an errand this afternoon and while I was out I was going to run by AutoZone to read the CEL. On my initial drive to my first errand the CEL was still there but after I was about to go to AutoZone the CEL went away. I still went to read what the CEL was and thats where I saw the 174 and 171 code.

Now I'm wondering if my tune is just off. I've only added a ported TB and the ADM scoop since it was initially tuned my ADM. Neither is supposed to require a re-tune. In addition I've had both those mods on for quite a while (several months) before I started this CEL issue.

I guess I'm going to start researching more about the SCT tunner and I'll probably be emailing Ted about my tuning options with him. I was hoping to not have to spend another $400 out of my mod fund but I guess I may have no other real option.

[JANNETTYRACING]

Originally Posted by caverman

Sorry Ted....I missed this question. After switching the two front O2 sensors the CEL went off automatically. I didn't clear them manually. The CEL eventually came back on a week or so later. I went back to AutoZone to scan it and it now said P0174 and P0171 were lean. It's possible that it might have said that before and I just missed the fact that it was reading two codes. So I cleared it again in hopes that if it came back on that it would say Bank 1 (initially it said Bank 2 before the switch) was lean.

Well, unfortunately a couple weeks later (which was last week) it came on again. This time it's saying both P0174 and P0171....bank 1 and bank 2 are too lean.

Wierd thing is that it came on last Thursday but didn't have time to go read it because I was going out of town Friday. I got back on Sunday (two days ago) and just got the chance to drive it today but my wife drove the car yesterday. I had to run an errand this afternoon and while I was out I was going to run by AutoZone to read the CEL. On my initial drive to my first errand the CEL was still there but after I was about to go to AutoZone the CEL went away. I still went to read what the CEL was and thats where I saw the 174 and 171 code.

Now I'm wondering if my tune is just off. I've only added a ported TB and the ADM scoop since it was initially tuned my ADM. Neither is supposed to require a re-tune. In addition I've had both those mods on for quite a while (several months) before I started this CEL issue.

I guess I'm going to start researching more about the SCT tunner and I'll probably be emailing Ted about my tuning options with him. I was hoping to not have to spend another $400 out of my mod fund but I guess I may have no other real option.

This is Where and SCT X3 would be a Great Help, You can Log and see what is actually happening.

I look forward to working with you.

Ted.

[caverman]

Originally Posted by JANNETTYRACING

This is Where and SCT X3 would be a Great Help, You can Log and see what is actually happening.

I look forward to working with you.

Ted.

Yeah.....I'll send you a PM soon.

Stupid CEL came on again so it didn't even last 15 miles this time.

[danielblack60]

i would become good friends with someone that works at a shop with a smoke machine...stuff a plug in the throttle body and one tail pipe, and shoot some smoke in the other tailpipe to make absolutely sure there are no exhaust leaks

if you can get your hands on a smoke machine i would also use it to check for vacuum leaks...who knows, maybe the lean code showing up after the exhaust was removed was a coincidence...i've seen wierder things happen haha

another thing to try is you can unplug the maf to force it into Speed/Density mode, you could watch your fuel trims and see if they go back to normal, normal fuel trims in SD mode = faulty maf sensor, or it may be dirty/contaminated with oil as previously mentioned.

i hope this helps you out. good luck fixing the problem man, i'm curious to see what's causing this