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Discussion Starter #1 (Edited)
I've been getting these codes for awhile now which are p0174 "ECM has detected a rich or lean air/fuel ratio on bank two" and p0171 "the power train control module uses the oxygen sensor to calculate the air/fuel ratio. The computer has recognized a rich or lean condition on one engine bank only" which confuses me because the other code says it's on bank two as well?

Now, Originally I thought it was my custom cold air intake I installed but I'm starting to believe it's not. Some symptoms is my cars idle seems to be rough intermittently especially when it's cold out and my gas mileage has went down.
I Thought it was a vacuum leak but I had it smoked checked and they said nothings showing. I even went with uninstalling in entirely and reinstalling to make sure there was no leaks.

Reset the ecu by unhooking the battery over night and I'm still getting the code.

It's saying the exact definition of this code is p0171 "fuel trim bank one condition" and p0174 "fuel trim bank two condition"

It says if these codes pull up together expect an MAF sensor fault (which I don't think it is, I even cleaned it with some CRC) 02 sensor but I don't know which sensor it would be. Bank 1 and 2?
Also it says it could be a fuel injector or misfire


I don't know where to start guys. Please Any help would be appreciated.
 

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Have you tried fuel injector cleaner? When was the last time you changed the plugs?
 

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well for starters its not plugs. he would be getting misfires, not lean conditions out the tailpipe. the ECU is quite sensitive to misfires. bad plugs and i'd expect to see the ECU reporting rich conditions.

injector cleaner is a waste of time and money. if an injector is clogged enough to cause this, it must be removed and cleaned properly.

i'd say its down to two possibilities:

-fuel system problem. either pump is failing and pressure is low or an injector is stuck and won't open fully. both conditions are relatively easy to test for. injectors all you need is a mechanics stethoscope. listen to each injector, should be a sharp snapping sound. the bad one will stick out easily. fuel pressure you'd need to put a pressure gauge on the system. pressure gauge isn't expensive, can be easily plumbed in with a T fitting and some extra tubing. pulling the line off the fuel rail and plumbing in there is probably easiest.

- air intake leak. visual check first, may be your CAI. check intake manifold gasket with some spray starting fluid. when it sucks some in, idle will pick up.

the fact that your FE has gone down could indicate something else as well...sensor fault is possible. cleaning the MAF doesn't really prove anything. you'd need to get a multimeter on it to test the resistance. resistance changes at different air pressures in the intake which is how the ECU knows what is going on.

finally yes the O2 sensor could be at fault....i'd be surprised as the ECU is usually very good at reporting a bad O2 sensor but it's possible. test would be similar, the bank 2 sensor is the downstream one after the cat.
 

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Discussion Starter #4
Have you tried fuel injector cleaner? When was the last time you changed the plugs?
Don't believe they've been changed yet. Car had 79k on it isually these plugs are good till about 100k no?
I've used techron chevron fuel injector cleaner maybe 3k miles ago
 

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Discussion Starter #5
well for starters its not plugs. he would be getting misfires, not lean conditions out the tailpipe. the ECU is quite sensitive to misfires. bad plugs and i'd expect to see the ECU reporting rich conditions.

injector cleaner is a waste of time and money. if an injector is clogged enough to cause this, it must be removed and cleaned properly.

i'd say its down to two possibilities:

-fuel system problem. either pump is failing and pressure is low or an injector is stuck and won't open fully. both conditions are relatively easy to test for. injectors all you need is a mechanics stethoscope. listen to each injector, should be a sharp snapping sound. the bad one will stick out easily. fuel pressure you'd need to put a pressure gauge on the system. pressure gauge isn't expensive, can be easily plumbed in with a T fitting and some extra tubing. pulling the line off the fuel rail and plumbing in there is probably easiest.

- air intake leak. visual check first, may be your CAI. check intake manifold gasket with some spray starting fluid. when it sucks some in, idle will pick up.

the fact that your FE has gone down could indicate something else as well...sensor fault is possible. cleaning the MAF doesn't really prove anything. you'd need to get a multimeter on it to test the resistance. resistance changes at different air pressures in the intake which is how the ECU knows what is going on.

finally yes the O2 sensor could be at fault....i'd be surprised as the ECU is usually very good at reporting a bad O2 sensor but it's possible. test would be similar, the bank 2 sensor is the downstream one after the cat.
I really do not believe it's the custom cold air intake. There is no leaks I'm sure of it.

I want to explain this as well. When I first put the intake on I did not get a CEL. After I drove for a couple months I got a CEL but it would come on an off and I only got it after I REALLY revd the engine. it still was giving the same codes now) but the CEL would go on an off. Then stay off for awhile and maybe come back on and my idle was NEVER rough intermittently.

Now the check engine light comes on and STAYS on (same codes) and my idles rough.

Could this mean/hint at anything?
 

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I've been getting these codes for awhile now which are p0174 "ECM has detected a rich or lean air/fuel ratio on bank two" and p0171 "the power train control module uses the oxygen sensor to calculate the air/fuel ratio. The computer has recognized a rich or lean condition on one engine bank only" which confuses me because the other code says it's on bank two as well?

Now, Originally I thought it was my custom cold air intake I installed but I'm starting to believe it's not. Some symptoms is my cars idle seems to be rough intermittently especially when it's cold out and my gas mileage has went down.
I Thought it was a vacuum leak but I had it smoked checked and they said nothings showing. I even went with uninstalling in entirely and reinstalling to make sure there was no leaks.

Reset the ecu by unhooking the battery over night and I'm still getting the code.

It's saying the exact definition of this code is p0171 "fuel trim bank one condition" and p0174 "fuel trim bank two condition"

It says if these codes pull up together expect an MAF sensor fault (which I don't think it is, I even cleaned it with some CRC) 02 sensor but I don't know which sensor it would be. Bank 1 and 2?
Also it says it could be a fuel injector or misfire


I don't know where to start guys. Please Any help would be appreciated.
Spray some intake cleaner around where the master cyl goes into the brake booster. Sometimes the o ring rots out and causes those codes. If the engine revs after you spray, then you found your prob. It's just ONE of the many places for a leak.
 

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I've been getting these codes for awhile now which are p0174 "ECM has detected a rich or lean air/fuel ratio on bank two" and p0171 "the power train control module uses the oxygen sensor to calculate the air/fuel ratio. The computer has recognized a rich or lean condition on one engine bank only" which confuses me because the other code says it's on bank two as well?

Now, Originally I thought it was my custom cold air intake I installed but I'm starting to believe it's not. Some symptoms is my cars idle seems to be rough intermittently especially when it's cold out and my gas mileage has went down.
I Thought it was a vacuum leak but I had it smoked checked and they said nothings showing. I even went with uninstalling in entirely and reinstalling to make sure there was no leaks.

Reset the ecu by unhooking the battery over night and I'm still getting the code.

It's saying the exact definition of this code is p0171 "fuel trim bank one condition" and p0174 "fuel trim bank two condition"

It says if these codes pull up together expect an MAF sensor fault (which I don't think it is, I even cleaned it with some CRC) 02 sensor but I don't know which sensor it would be. Bank 1 and 2?
Also it says it could be a fuel injector or misfire


I don't know where to start guys. Please Any help would be appreciated.
Spray around where it fits in the booster. image.jpg
 

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Climate might be the culprit. I got the cel light on this morning during daily spirited driving on my commute to work. However, today is considerably colder than usual. I'm pretty sure it's the lean codes (I will check when I get home). Have u noticed it happening on colder days?
 

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Discussion Starter #10
Climate might be the culprit. I got the cel light on this morning during daily spirited driving on my commute to work. However, today is considerably colder than usual. I'm pretty sure it's the lean codes (I will check when I get home). Have u noticed it happening on colder days?
Only started during the winter. Summer was fine
 

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Climate might be the culprit. I got the cel light on this morning during daily spirited driving on my commute to work. However, today is considerably colder than usual. I'm pretty sure it's the lean codes (I will check when I get home). Have u noticed it happening on colder days?
the car is designed to work in any climate that the OP is going to experience where he/she lives. if the weather change is causing the engine to lean out, something isn't working right. climate is not the culprit, its causing the culprit to act up.
 

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Discussion Starter #12
the car is designed to work in any climate that the OP is going to experience where he/she lives. if the weather change is causing the engine to lean out, something isn't working right. climate is not the culprit, its causing the culprit to act up.
Went ahead and tried this test first. I sprayed from what I can see every vacuum line with some CRC carbueeater cleaner and there was no spike in the engine. (Which I don't think it is in the first place) so I'm debating on ruling a vacuum leak out
 

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Discussion Starter #13
I also unplugged the MAF sensor to see how it runs without it. When unplugged it ran fine. Then I plugged it in an idle dipped a little. I re tried and when I unplugged car stalled.

I think this is normal correct?
 

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the car is designed to work in any climate that the OP is going to experience where he/she lives. if the weather change is causing the engine to lean out, something isn't working right. climate is not the culprit, its causing the culprit to act up.
im aware that EFI cars unlike carburated cars automatically adjust to different climates (FYI people with upgraded turbos often have to tune during seasonal or altitude changes). however the car was not designed with a 3" CAI. perhaps in the air density under colder weather at WOT through the CAI is more than the MAF can read and accurately causing the car to lean out.
 

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i'll buy that, its a possibility. test: stick the original intake back on and see what happens. not a hard job at all.

good work with the carb cleaner, did you try around where the intake manifold mates with the engine head? that would rule out a leak in the intake gasket....or close to anyways.
 

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Discussion Starter #16
i'll buy that, its a possibility. test: stick the original intake back on and see what happens. not a hard job at all.

good work with the carb cleaner, did you try around where the intake manifold mates with the engine head? that would rule out a leak in the intake gasket....or close to anyways.
I wish I could but I lost a piece from the OEM intake that connects one of the plastic pieces. It's one of the interlock pieces that connects the plastic pieces -_- Not an entire tubing. I guess basically like an adapter

And you're reffering to this area right (where the last red coupler connects to the engine right?
 

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Discussion Starter #17 (Edited)
The piece closest to my headlight (square looking piece) connects to the bottom of the long plastic tube (next to it) but it doesn't fit securely in the hole opening. Meaning there had to be an adapter or piece that connects it securely that I must have misplaced :(
 

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Discussion Starter #18
i'll buy that, its a possibility. test: stick the original intake back on and see what happens. not a hard job at all.

good work with the carb cleaner, did you try around where the intake manifold mates with the engine head? that would rule out a leak in the intake gasket....or close to anyways.
Also, I've noticed my idle picks up whenever I turn the heat on. Could this indicate anything or is that normal?
 

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that is interesting...does it do the same with the fan off? i'm guessing not...if it does very strange. have to think on that one for a while.
 

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Discussion Starter #20
that is interesting...does it do the same with the fan off? i'm guessing not...if it does very strange. have to think on that one for a while.
Correct me if I'm wrong but I don't think the fan goes on unless you put it on defrost?

I had it on just through the front vents

I'll check if it does it again on my way home from work
 
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