07 Outlook, P0171, P0174, and "Service Stabilitrak" after replacing plugs!

[mike1161]

Our 07 Outlook just turned over 100K miles, and new plugs were recommended. So I put in Autolite platinum plugs (gapped per service manual). Started it back up, and the idle was kind of rough, with the RPM "hunting" up and down a bit. Then I get the warning bells with "Traction Control Off" and "Service Stabilitrak". What the heck? I've cleared the codes a few times, but they come back. And the "Traction Control Off" and "Service Stabilitrak" comes and goes. I also tried disconnecting the battery for a few minutes to see if that would clear up the Stabilitrak issue, but no luck. I saw one other post on here where it said that there is a wire bundle that goes to the camshaft position sensor and if you bend it or mess with it, that could cause the Stabilitrak issues. Any ideas?
And for the P0171, P0174 codes below is something I found: seems reasonable, but where to start? Especially since it was running perfect before I changed the plugs! Note: Air filter is brand new also.

Code P0171 may mean that one or more of the following has happened: The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak downstream of the MAF sensor Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor Possible Solutions A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include: Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling Inspect all vacuum and PCV hoses, replace/repair as required Inspect all hoses and connections in the air intake system Inspect and/or test the intake manifold gaskets for leakage

[Penrod]

I tried cleaning the sensor after I had similar faults but it didn't work. I replaced the MAF and everything worked fine. I wound up messing up my throttle position sensor and had to replace it also, but that's a completely different issue. I think I actually messed up the MAF while working on an idling issue.

[mike1161]

Thanks, I may try that. I'm just wondering if the stored codes are somehow related to the Stabilitrak issue, since they started at exactly the same time. By the way, I've been clearing the codes and then driving it a bit, and sometimes it takes a few minutes to get the codes back. But the Stabilitrak issue seems to pop up first, and then just keeps coming and going (i.e., error turns on and off by itself). I read in another thread that the Stabilitrak issue could be caused by one of the timing chains going bad. This would be a big deal, because according to my Haynes manual, to replace those you have to pull the motor out.

[Penrod]

If it is a timing chain you may be covered by the extended warranty for your vehicle. Look at a thread on here about timing chains and I think someone explains the extended warranty for it.

[mike1161]

Well, I'm still having both of these problems continue. For the P0171 / P0174 issues, I looked everything over in the engine bay for vacuum leaks, but so far couldn't find any. So yesterday I swapped the old spark plugs back in to see if that could have been the problem. Nope. So my next step is to probably replace tube PN 12611354. It's a tube that goes from the manifold to the evap canister, and seems kind of loose fitting.
And for the "Service Stabilitrak" issue, I read on another posting that there are 4 metallic rings (one at each wheel), with sensors on them. If there is too much dirt buildup on them, and some kind of metallic particles get attached, they could mis-read. So yesterday I took all 4 wheels off, and thoroughly cleaned all the sensor rings. But that didn't solve it either. Well at least I ruled a few things out.
The saga continues....

[fdryer]

It appears you have two separate issues, lean fuel mixtures - P0171/P0174 and Stabilitrak.
This may help; http://repairpal.com/OBD-II-Code-P0171-and-P0174. Stabilitrak is part of ABS; wheel speed sensors, wiring to each sensor and four reluctors. While examining each reluctor didn't expose a damaged one leaves wiring and sensors to check.

[mike1161]

Yes, I agree, very likely 2 separate issues, but very odd how they both started at exactly the same time, when I changed the plugs. I keep thinking maybe I accidentally pushed on a wire bundle or something while I was working in there.

Thanks for that link on the P0171, P0174 issue. It seems to confirm what I'm thinking, that somewhere there is a vacuum leak. I did just order the hose that goes from the manifold down to the little valve that controls the evap canister. I do remember disconnecting that hose because I thought I may have to take one of the other shrouds off, but didn't have to after all. Maybe it cracked? I'll replace that when the part gets here & then we'll see.

And for the Stabilitrak problem, when I cleaned the sensors and rings, I also looked at the wiring the best I could, but didn't notice anything wrong. That may be a tougher one to figure out....some other postings have said it can be caused by any number of crazy things. Not sure if all of these are true or not. There's a lot of postings on other message boards, since this motor is widely used on other GM vehicles.

[fdryer]

In the S-series forums, the ABS light and erratic xmission shifts always pointed to battery failure. No battery light. A Nissan Sentra's battery and brake light pointed to alternator failure. It would appear for some electronics being sensitive to voltages may give false error codes yet point to something unrelated.

[mike1161]

Thanks, I will keep that in mind too. I guess the next thing I'm going to do is swap the new plugs back in, and then install the new tube that goes from the manifold to the evap canister (when it gets here, supplier still hasn't shipped it yet).
If that doesn't work, I'm thinking of changing out either the throttle body or accelerator pedal sensor (have seen quite a few posts saying this solved the Stabilitrak error). And I'm thinking that could make sense, because over the weekend, I had to make a 100 mile trip, and noticed that the Stabilitrak warning seemed to always pop up when I made a change in the accelerator pedal position. I.e., when cruising steady-state, the error always went away, but almost as soon as I took my foot off the gas, error pops up.
Note: battery is fairly new, so "should" be OK, but I haven't measured it's voltage with a DMM yet; may also check that to rule it out.

[mike1161]

PROBLEM SOLVED!!!
Last week I swapped the new plugs back in, and also installed the new tube that goes from the manifold to the evap canister (although the old one didn't look bad, but I suspected a bad O-ring in the connection). I cleared the codes, and then before I started it back up again, just took one last look around in the engine compartment, because I was still thinking it really seemed like a vacuum leak. And then I saw it! There was an open vacuum port / fitting on the rear of the manifold (hard to see because it faces towards the firewall). And then I remembered that I had found a piece of rubber, kind of like a sealing cap, from when I first worked on it, but didn't know where it went! That's when I had the "ah-ha" moment!
So I put the rubber piece back on, and guess what? No more P0171 or P0174 codes, no rough idle, and also no more "Service Stabilitrak" errors! I've driven it quite a bit to confirm that it's OK. Boy, did I feel dumb!
So somehow, the vacuum issue was also causing the Service Stabilitrak issues also. Crazy, but true.
I am one happy camper now.

[fdryer]

Great find!? By chance is this vacuum leak from the green fitting, used for evap testing?

[mike1161]

Yeah, what a relief!! And no more parts to buy! Not sure what the "green fitting" is, but it was just a metal tube about 1" long & maybe 1/4" or less diameter, the rubber cap on it was black. It would make sense that it was just for testing, since in normal operation it's capped off.

[Reefgal]

THANK YOU for this info! Changed the plugs in my Outlook over 2 weekends- had to get the courage up to tackle those rears- and this exact scenario happened.
I was the rock star when I said after about 40 minutes of poking around in the engine.....," hey, do you see a little uncapped tube back there?"

[Lowarcher]

I am experiencing the same issue with the service traction control and codes 171,174. I have located the small port on the back of the manifold but cannot locate the rubber cap that goes on it. I have called auto zone and the Chevy place but no luck on replacing it. Any ideas on what I can do to find a replacement cap?

[Bst1112]

When I bought mine couple months ago, I had the same issue after changing spark plugs, took it back to the dealer and they fixt it saying there was something loose and couple months later I'm having the same issue. Do you guys have the part number by chance? Or where to buy the hose. THANKS!!!

[justplainatom]

07 Outlook XR. Car began to idle hard and no acceleration past 15mph. Dashboard says "Engine Power Is Reduced" "Traction Contol Off" "Service Traction Control" "Service Stabilitrack" had to leave it at the dealership. Please Advise.

[Data]

Hello there, any way to get a picture of where the cap is? As i too have p0174 and stabilitrak error.

Thanks