KVS84

Fella's


My 07 V has been throwing P0171 Lean Mixture codes on and off since I bought it 6 months ago. Its under CPO, so last week when the light came on i dropped it off at the local dealer. Different dealer 5 months ago tested everything (o2 sensors, MAF, IAT,) then cleaned injectors and said we dont know give it a try with clean injectors. Well since then it's always ran lean intermittently tripping the light. Dealer today tells me its because I'm running 93 octane fuel and the engine is designed to run 87.... .... I'm seriously speechless. I assume everyone is running premium?


-Keegan

chitown21y

iTrader: (6)

Another dealer that has no clue. Maybe if it was bad gas but if not its not the gas. I run 93 all the time no issues. Tell them to pull a new V off the lot and put 93 in it and show you the same code. Won't happen.

DMM

Hmm...you say the injector cleaning didn't work huh? Is there anything that gasoline pressurized to 55 PSI won't clean? -Those BTW are words directly from GM drivability and electrical Engineer Nick H.-

The fuel octane rating will not cause a lean mixture, I would insist on a shred of documentation to substantiate that. These guys are idiot's, speak with the Service Manager and insist that a T.A.N.S. case be initiated (and get the case number and the Engineers name for reference). I stopped by my old dealership two days ago and found that as the warranty times get lower and lower the knowledgeable techs are leaving the dealerships in droves and are leaving the parts changers behind to service everything.

Do not let them shoo you out the door with a line of bullshit since they cannot fix your car.

RADEoN

iTrader: (12)

I didn't know I didn't have to run premium. No ****.

whisler151

I'm pretty sure the manual says a minimum of 91 is recommended.

I cant believe a dealership told you that...ridicules.

KVS84

Well today the story changed. After I ripped the service advisor about the octane requirements of 10.6:1 compression engine (i'm a BMW/Audi tech) he's now saying even though its lean at +17% it has to be above 20% to turn the light on so it's considered normal right now. I'm bummed I payed extra $ for a car under CPO when Im going to have to fix it anyways..... ugghhh.

Thanks for the comments guys.

-Keegan

Scott96LT1

iTrader: (2)

That's ridiculous that you have to go through that. Plus I just can't believe the one dealer blamed it on premium gas. I'd be surprised if anyone with a V put regular in the tank unless they were in some kind of bind. I'll never put anything below 91 in my V or my Z.

-T-

iTrader: (2)

I'm slightly confused Your check engine light is on with a 17% lean condition. Where did this number come from? What scale? Anyways, but it is only supposed to turn on at >20% lean condition. So then there is a problem, since its on at 17 instead of greater than 20!?

If you are under warranty, and they refuse to fix your car... I'm pretty sure you could own a few of their V2's outright when the lawsuit finalizes. I'm not really sure how this isn't a known problem with a TSB issued and they are saying that there is not problem. The light just feels like coming on. Slap that dipshit!

Stepside

If you recently purchased gasoline and experienced the 'service engine light', then the probability is that the gasoline is the cause.
Add some 'Sta-Bil' to your gas. Takes almost 100 miles to get results.

When was the last time the fuel filter was changed?
87 Octane??? Whoa!! - - 91 octane or higher is the recommended as previously mentioned.
This is for the dealership.

KVS84

The car has always run lean since I bought it. First dealer swapped a bunch of parts but could not get the fuel trim to come back to 0. Since then I check it periodically and it's always lean but only a couple times has it gone lean enough to trip the light. Car runs great, no other driveability issues or codes. I'm gonna do a volume check of the fuel pump tomorrow when I get the car back and plan on changing the fuel filter this weekend.

aurora40

iTrader: (1)

Just FYI, your fuel trims don't have to be 0. That's why the trims exist. If it's adding fuel, it doesn't mean the engine is running lean. It means it had to add fuel to run at stoichiometric, which is where it's running.

However, obviously the light coming on means something is wrong.

Since it seems like you're gonna have to do some troubleshooting on your own, are both banks showing the same behavior in terms of fuel trims?

KVS84

I'm a German car tech so I understand how fuel trim works. Both banks are always lean but just under the limit for tripping the light. When a code is set only p0171 for bank 1 comes up even though bank 2 trim is only slightly behind bank 1. I don't own a Tech 2 scan tool so I'm just using the generic OBD II function on a PC based BMW scanner.

greddy91

iTrader: (2)

I'm an American computer nerd so no matter how this story is spun it sounds like total bs to me. If we were all running around with glowing amber dashboards I'd be more inclined to forgive the dealer, but we're not, and there is an issue they are refusing to resolve.

This is total BS and makes me glad I didn't fork out $1300 for the GMPP when it was available to me.

siggyfreud

iTrader: (1)

Have you or the dealer considered that it may not be the fuel system, but the MAF system that is providing incorrect readings?

-T-

iTrader: (2)

^... or a leak after the maf reads and calculates? Intake pipe, throttle body to intake mate, intake crack. MAP not seated properly or broke.

KVS84

Swapped in a new MAF no change. Sprayed down Intake base gaskets, throttle body, intake tube, etc. no leaks.

I got my Snap On dealer to loan me a Modis scan tool for a few days that has GM software instead of using a generic OBD II scanner. Monitored fuel trim and O2 sensors on the drive home (about 30 miles highway and back roads). Noticed the short term fuel trim to be perfect. Cross counting + and - a few percent. The long term however was changing with throttle on and off. Shouldn't long term be an average and not change instantaneously? Cruising speed + 9 bank 1, +7 bank 2. Let off the throttle instantly changes to + 17 and + 13. Back on the throttle down to + 7 and +6. Meanwhile short term never goes beyond 5% in either direction on both banks.

aurora40

iTrader: (1)

It is an average, but there are "cells" based on RPM, MAP, etc, that have their own trims. You should be able to see what cell it is in, and the long term trim will change as the cell changes. It's not changing due to short term trends, at least not based on what you are describing. When you go back to that first cruising cell, it should be +9/+7 again, and so on.

I may be using the wrong term for it now, though. I'm used to it being multipliers and integrators, and they were called block learn cells then. Maybe they have a different name.

KVS84

Thanks Aurora you are correct. I need to figure out this Modis thing to view the cells and go for another spin. The crazy germans use idle and part throttle trims. None of this short term long term stuff. Making my brain hit the way back button

JJSimon904

iTrader: (8)

I had this problem when I first got my car too. We narrowed it down to happening only when it was hot outside after running the car hard. They replaced everything under the sun, looked for vacuume leaks, etc. They never figured it out and it went away as fall/winter came.

I later figured out the car had a crap tune in it. Everything appeared stock when I bought it so the tune was probably for whatever mods were done and it was a poor tune at that. I think that is what was causing my issues because once I put the cam in and started tuning from a real stock tune, I never got the code again.

greddy91

iTrader: (2)

And that's why we won WWII...

Germans were all idle on the frontline thinking about their trim, and our guys were calculating the size of the cells for their long term imprisonment...

Loosely translated.