Dtc P0171

Hi all,
I got this code after failing an emissions test. I've searched these forums, and found out what the DTC P0171 means. But I want a little help in what needs to be done.

The car has a weird noise to it, almost sputtering sound. I found out it was coming from a hole in my muffler/resonator.

Now, I've had electrical problems in this car before (defective MAF sensor), but I'm wondering (hoping) the hole in the muffler would give this error code.

The weird thing is, the SES goes off and on. When I took it to a dealership, they couldn't diagnose it, because the light was off and told me nothing was wrong with my car.

Just looking for a little help. I'm going to take it to a friend who owns a shop so he can fully diagnose it.

Regards

P0171 System too Lean (Bank 1)

This is a generic code, and could be caused by many different things including a partially clogged fuel filter, vacuum leak, worn throttle body, borderline oxygen sensor, etc.... It's a very difficult code to properly diagnose, as not only one component can cause it.

P0171 System too Lean (Bank 1)

This is a generic code, and could be caused by many different things including a partially clogged fuel filter, vacuum leak, worn throttle body, borderline oxygen sensor, etc.... It's a very difficult code to properly diagnose, as not only one component can cause it.
I was afraid of that.

Could a hole in the muffler/resonator cause this? I just want to start pricing my repair now before I get it fully diagnosed.

Thanks for the reply.

Since the muffler and resonator are downstream of the catalytic converter and oxygen sensors, I'd say no. The front o2 is what determines if the system is lean or rich, so it has to be an issue on/in the engine itself. If it's the GTP in your signature, have them check both the lower intake gaskets and the supercharger base gasket for vacuum leaks first, as these are areas known for causing a lean condition.

Since the muffler and resonator are downstream of the catalytic converter and oxygen sensors, I'd say no. The front o2 is what determines if the system is lean or rich, so it has to be an issue on/in the engine itself. If it's the GTP in your signature, have them check both the lower intake gaskets and the supercharger base gasket for vacuum leaks first, as these are areas known for causing a lean condition.
Ok, now I'm getting a little worried.

About a month ago I had to have the lower intake gasket & supercharger gasket replaced. Think the dealership could have did a bad job with those tasks? The thing is, they wouldn't replace the valve cover gasket without an extra $115, so I declined. The SES starting coming on about a week after I picked it up from the shop.

Also, I notice at idle, the motor shakes in a odd manner.

What's weird now, is that the SES light is off. But it'll come back on soon I suppose, like it's been doing.

did they replace the injector o-rings? I would just start looking for a vacuum leak

did they replace the injector o-rings? I would just start looking for a vacuum leak
I have no clue. They are so vague on what they do. You have to drill them for information.

I'm going to call and ask them after work.


Also, I have to pass the emssions test to renew my license plate registration. If the SES light isn't on, could I pass the test?

Also, I have to pass the emssions test to renew my license plate registration. If the SES light isn't on, could I pass the test?

To pass the odb-ii 1996 and up emissions test in most states that require it you have to get an emissions (IM) readiness flag as being OK. IM status will be checked by the scan tools they use. It is possible to get a IM status OK without the SES/CEL light on but certain DTCs will inhibit IM readiness and cause it to fail so you may flunk inspection again. I have a better than average odb-ii scanner and check IM status right before the annual emissions test in Texas just to be sure it is good.

Why were the supercharger and LIM gaskets replaced and with your low mileage? The P0171 DTC is one of the worst to get and may involve alot of controlled substitution of suspected parts and diagnostics.

At least on the front valve cover gasket you can now get that replaced free of charge. :grinyes:

See link below.

http://www.automotiveforums.com/vbulletin/showthread.php?t=893778

To pass the odb-ii 1996 and up emissions test in most states that require it you have to get an emissions (IM) readiness flag as being OK. IM status will be checked by the scan tools they use. It is possible to get a IM status OK without the SES/CEL light on but certain DTCs will inhibit IM readiness and cause it to fail so you may flunk inspection again. I have a better than average odb-ii scanner and check IM status right before the annual emissions test in Texas just to be sure it is good.

Why were the supercharger and LIM gaskets replaced and with your low mileage? The P0171 DTC is one of the worst to get and may involve alot of controlled substitution of suspected parts and diagnostics.

At least on the front valve cover gasket you can now get that replaced free of charge. :grinyes:

See link below.

http://www.automotiveforums.com/vbulletin/showthread.php?t=893778
Thanks for your reply.

Upon taking my car because of it misfiring.
They inspected it.
1.) MAF sensor was replaced due to it being defective.
2.) #1 coil was replaced, cause of misfire.
3.) Supercharger gasket was leaking coolant
4.) LIM gasket was leaking

Were these external coolant leaks or internal where coolant was being consumed in combustion?

Were these external coolant leaks or internal where coolant was being consumed in combustion?
I'm not exactly sure.
This is something else I'll have to ask them. Talking to these guys is painful.


I just called them, they're telling me the code could be a defective cat, or gas cap leak.

I'm more inclined to take you guys advice, as it seems they are trying to cover themselves from what they did wrong on their work.

The reason why I asked is to to determine if any action should be taken on the front 02 sensor since this component can set off the DTC. It may have been contaminated with unburned coolant going out the exhaust. Unburned coolant could also damage the CAT convertor. Proper 02 sensor diagnostics requires that the 02 sensor be checked for proper operation with a scan tool. 200 to 800 mv (.2 volts - . 8 volts) and to make sure it is not lazy.

I don't believe the P0171 DTC is a result of a large leak in the evaporative emissions system (Gas Cap Code). Plus you would have a DTC related to that.

I would explain to them the SES/CEL light with the P0171 DTC came on within a reasonable period of time after their work and demand warranty action.

Plus if the CAT is bad it should be replaced free of charge since there is a notice about it for 2001-2002 models. Notice is at our Tips & Maintenance forum.

http://www.automotiveforums.com/vbulletin/showthread.php?t=681283

The reason why I asked is to to determine if any action should be taken on the front 02 sensor since this component can set off the DTC. It may have been contaminated with unburned coolant going out the exhaust. Unburned coolant could also damage the CAT convertor. Proper 02 sensor diagnostics requires that the 02 sensor be checked for proper operation with a scan tool. 200 to 800 mv (.2 volts - . 8 volts) and to make sure it is not lazy.

I don't believe the P0171 DTC is a result of a large leak in the evaporative emissions system (Gas Cap Code). Plus you would have a DTC related to that.

I would explain to them the SES/CEL light with the P0171 DTC came on within a reasonable period of time after their work and demand warranty action.

Plus if the CAT is bad it should be replaced free of charge since there is a notice about it for 2001-2002 models. Notice is at our Tips & Maintenance forum.

http://www.automotiveforums.com/vbulletin/showthread.php?t=681283
Hopefully when I take my car to get it fully diagnosed we're find the problem. And no, I highly doubt it has anything to do with my gas cap either. That was the first guy I spoke to at the dealership, the second guy mentioned a bad cat.

I did notice, what appears to be dried coolant on the front headers, around the gasket. I'll take pictures when I get off of work.

I had the cat replaced, and the resonator removed, still same problem.

I also forgot to mention initially in this thread, I've felt the car to be a little sluggish.

I'm going to replace the fuel filter and PCV valve either today or this weekend. I'm also going to try and find a vacuum leak around the gaskets. If that doesn't work, I'm going to try and take a look at the o-rings.

Any tips on getting to, and replacing the o-rings, and possibly cleaning the injectors?

the injectors arent so bad to replace on the 3800. Make sure you coat the new ones with grease so they slip in easy.

I'd just grab a can of carb spray and start spraying at things listening to see if the RPM increases.

Make sure you coat the new ones with grease so they slip in easy.

This is so true with many other "things"... :smokin:

Anyhow, thanks for the tip.

Also, please tell me the fuel rail comes out easy on my year & model GP. Meaning without disconnecting a bunch of lines.

Actually it does come off easy comparatively speaking and you can leave both pressure and return lines connected to the fuel rails.

This is so true with many other "things"... :smokin:

Anyhow, thanks for the tip.

ah HA HA HA HA....

Man, that sort of sounded bad, didnt it?

No pun intended

Good luck man, I'd just bet you'll find a vacuum leak somewhere, maybe one connected wrong, or a plastic one split. Check it all over, you'll find it.

Yeah, I'm thinking someone at the dealership did a half ass job replacing one of the gaskets. This saturday I'll get tackle it. Thanks

Didn't get a chance to find the leak. But I replaced the PCV valve and fuel filter. Hopefully that does it.

Also, just wondering, neither did the old or new PCV valve had a rubber gasket, is that normal?

The PCV is supposed to have an o-ring seal. New PCVs do not normally come with one so it has to be taken off the old PCV during replacement or get a new one. The missing o-ring will normally cause an EGR flow problem and set off DTC P0401 once the PCM runs the test and it fails.

The PCV is supposed to have an o-ring seal. New PCVs do not normally come with one so it has to be taken off the old PCV during replacement or get a new one. The missing o-ring will normally cause an EGR flow problem and set off DTC P0401 once the PCM runs the test and it fails.
Oh great, this is what I thought. But when I called Autozone, they couldn't find anything about it, and said I might not need one.

Where can I get this part at real quick? Is there a part# of some sort?

Thanks

You should be able to find an o-ring that fits at Autozone from help parts or whatever o-rings they carry. Just take the old PCV with you and find a match. Other option is the local GM dealer. See link below to see what it looks like.

Click here (http://macgp.clubgp.com/howto/pcv/pcv.html)

Thanks, I saved the old PCV valve. I'll head to autozone after work.
Again, thanks a lot. If you charged for consulting I would gladly pay you for all the help you've given out.

If you're ever in Chicago, I can show you a great pizza place. My treat. :grinyes:
You too tblake

Ha Ha, thanks for the offer. Hope you get her going good.

Bob, will that o-ring fix his "system too lean" DTC also?

How could a shop forget to put it back in? Do they even need to remove the pcv valve to put LIM gaskets in? I though it could be left in the supercharger???

Ha Ha, thanks for the offer. Hope you get her going good.

Bob, will that o-ring fix his "system too lean" DTC also?

How could a shop forget to put it back in? Do they even need to remove the pcv valve to put LIM gaskets in? I though it could be left in the supercharger???
To be honest with you, I wouldn't put it past these guys. I don't trust their skills, nor was I there to see what they did.

I'm going to check around to see if they missed anything else. Namely those fuel injectors.

Yeah, I would. Then send the bill to them.

Can you tell when the code is being thrown?
I would think it's probably a vacuum leak if it's happening at idle & probably fuel delivery if it's happening at high rpm/wot.

Can you tell when the code is being thrown?
I would think it's probably a vacuum leak if it's happening at idle & probably fuel delivery if it's happening at high rpm/wot.
Always low RPM. Either at idle, or when cruising on the highway. So far, after the fuel filter and PCV valve change, it hasn't came back.

NICE!! Good work. Lets hope problem solved.