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Service Stabilitrak, Traction Control lights ON, alone with check engine light...

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Equinox This SUV offers a smaller, sportier stance than the Trailblazer, all without compromising the SUV abilities.

Chevrolet Equinox
Platform: Theta

Service Stabilitrak, Traction Control lights ON, alone with check engine light...

Old December 31st, 2016, 8:42 AM
  #91  
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Everything seems fine after a few days. The transmission leak (i believe it was just lines) was not related to the stabilitrak issue. It was apparently the EGR valve and the EGR pipe. I think the pipe was the key here. The EGR valve work was about $600. The tranny work was $500 then $200 for flush/fill. Got tagged with some required semi-annual maintenance for $60 (generally a brake inspection), add the tax, and there you go. Just amazed that I was charged 2 hours of labor for the EGR valve work since this is sitting right on top of the engine.
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Old March 7th, 2017, 5:26 PM
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Originally Posted by ruley73 View Post
In our case, the SS/STC messages and the check engine light were on before replacing the EGR valve in February 2011 at about 61k miles. After replacing the EGR valve (installed a new AC Delco part), the messages seemed to go away.

However, shortly afterwards I discovered I could replicate this same issue in the manner described below; EXCEPT that the check engine light would not come on.

If I floor the gas to downshift at about 55-60 MPH and don't let up, at about 90 MPH the Service Stabilitrak/Service Traction Control warnings (no check engine light) will appear just before the transmission shifts into fourth gear. The transmission upshifts harder while the message are on. It is not much harder, but definitely harder than normal. However, after parking and letting the vehicle sit for a few hours, the messages disappear and the transmission shifts fine until the messages are invoked again.

By this time the vehicle was out of the 50k mile extended warranty, I didn't think the 5yr/100k mile Powertrain warranty would cover this issue, and I had to exceed the speed limit by a wide margin to replicate it so I never brought it to the dealership so it could be addressed. Within the first couple months we bought it in October 2008 the SS/STCS warnings were appearing so they replaced either the BCM or the EBCM under warranty. I think it was the BCM, but I can't remember which one for sure though.

The only other time the warnings have appeared is during really long trips after driving for 100+ miles with the cruise set at 75 MPH (5 MPH above posted limit - the norm for around here). Three of the four wheel hubs & ABS sensors have been replaced (due to worn bearings). I recently cleaned the throttlebody, MAF sensor, and EGR valve. I can still invoke the warnings like I said before, but the wife just took it on a six hour trip and didn't have a problem.

I stopped by AutoZone and borrowed their scan tool on a couple different occasions with the messages still on (check engine light was not on). In both cases, the trouble codes I got were:

C0561 (confirmed DTC) - indicates that there are no problems in the ABS/TCS system; only that Stabiltrak is disabled

P0404 (pending DTC) - EGR valve is not opening or closing in accordance with engine computer (ECM) requests

P1779 (pending DTC) - I found a few slightly different interpretations/definitions of this code when researching it. This is going to get complex, but follow along....The definition that actually makes the most sense to me for the Equinox is "Engine Torque Delivered to TCM Signal" in conjunction with "the TCM will default driver requested torque data to 300 N m/221 lb ft." My interpretation is that the ECM is telling the TCM "the engine is currently producing X amount of torque", but the TCM is saying to the ECM "the data I am receiving from my own sources proves the engine can't be producing X amount torque. Since I can't trust what you're telling me, I will assume that the engine is always producing full output [300 N m/221 lb ft torque]. This will ensure that I can still meet your needs by shifting gears when I need to, but the shifts won't be as smooth as they normally are."

No, the ECM doesn't have a built-in dynamometer. It is using a programmed algorithm which takes into account information gathered from various sensors to calculate an estimated output value to communicate to the TCM so the TCM can make the transmission shift smoothly. The 3.4L engine produces about 210 lb ft of torque, so I believe the elevated figure of 221 lb ft of torque was probably chosen just to play it safe.

So, the order of events is most likely...
1) a malfunctioning EGR valve triggers P0404 which...
2) causes the ECM to send incorrect torque values to the TCM; thus triggering P1779; then...
3)the computer that controls Stabilitrak disables it because it determines that the previously detected faults (P0404 and P1779) may cause Stabilitrak to not function properly; thus triggering C0561

Even with the messages on, I've confirmed that only Stabilitrak is disabled like the DTC says. The Traction Control and ABS features remain fully functional. I'm hardly worried about Stabilitrak being disabled. I'm a lot more annoyed by the warning messages than I am worried about Stabilitrak not working. I've only been able to get Stabilitrak to engage on dry pavement once in the seven years (almost 100k miles) we've owned it anyways. Even then, it was in a large, vacant parking lot with a lot of effort. It has neverengaged when driving it down the road. I'm not trying to downplay Stabilitrak's effectiveness. I'm just saying it is really hard to get it to engage.

I hope my explanation makes sense to others and helps people understand what's probably happening. The only part that doesn't add up to me is why the P0404 and P1779 codes are pending and not confirmed.
I wonder if there may be an updated ECM or TCM calibration that we don't know about which might correct this issue.

Additional input/feedback from experts or techs would be welcomed and appreciated.
Maybe this trial and error 'tale' will assist others if they try the actions that I FINALLY got to that resolved the issue and then work backwards from there it that doesn't work for them. Just sometimes the simplest possible solutions are in fact the real solutions.

I had pretty much all the above symptoms with my 2007 Equinox (135,000miles on the clock).....Service Stabilitrak/Service Traction Control warnings and check engine light came on one bright sunny morning for no apparent reason. Vehicle drove and handled as per normal. No changes to anything: driving pattern/maintenance/climate etc.. immediately prior to this manifestation.

......searched a hundred plus blogs by means of research (at this point I should point out that I have not been mechanically minded AT ALL for the last 45 years but, as we are stuck in the USVI for a short term with a dearth of even half-decent mechanics or shops that don't ask $50 just to lift the hood!) we had to take matters into our own hands so to speak!

First off, after much reference to internet, I decide to get brave and change the EGR valve. Looked an easy job , even for me. So got one online from Rock Auto........it turned up in good time BUT was (despite website and invoice saying the Dorman product was of 'Origin in USA") made in China and didn't fit properly. Returned it with no problem; good site despite this hiccup. Got a replacement genuine GM part. Problem still existed though.

Then mech hunted down and dragged a 'friendly' mech with a major set of decoder devices to analyse the computer. Got C0561/P1779/P0404. Codes all diagnosed as results above. Odd given EGR replacement, but hey what do I know.

My 'friendly' mech then suggested that a fault in the main 80 amp fuse could produce these results; looked on web saw these going for $23 upwards, hunted round locally and (still my beating heart!) without a great deal of optimism after trying 4 other local autopart outlets decided to drop by the local GM dealer just for a laugh. Expected to be royally stiffed BUT got the last one (yep the last one until the next container ship of parts turns up in 2 months!) for just $13!!! Raced home, well sort of given the roads here, to fit the fuse..........fitted.......no change in lights/code.

Ditched the 'friendly mech' and read chevy blogs online some more, well for almost 24 hours.......... Boy are there a ton, hundreds/thousands of owners suffering from similar problems and getting massively stiffed by Chevy dealers who deny there is a recognised issue!!!

The most sensible course of action (and coincidentally the cheapest!) as recommended on here was to buy some Chevron Techtron Fuel System Concentrate and ALSO (significant!!!) some throttle body cleaner. Given our current location, probable dirty fuel/burn, my gut warmed to this as a solution.

Next day (today, 7th March 2017 in fact) $18 lighter and armed with these 2 cans of 'elixir' I attacked the problem. Obviously the Techtron 'might' take ages to resolve any problems, so I moved on to the TBC.

Heavens decide to open so had to do this in a tropical downpour.........nonetheless it was a very simple and easy job for even a novice like me! My dearly beloved had to interact by depressing the throttle pedal to allow me to clean the gunk off the butterfly valve in the throttle body.......... man there was some real 'crap' in there, looked like dark treacle.........but with the aid of an old toothbrush we got most of it cleaned.

The moment of truth..........turned on the ignition, fired it up....................NO lights!!! Let the idle settle and sort itself out with the onboard computer settings for 5 minutes to............then turned it off. The second moment of truth.......back on no lights................... hallelujah! Still not wanting to believe my layman's luck, I drove off for 20 minutes, parked, stopped, engine off, engine on, no lights!

Repeated process........all still good.......... will only report back if it all goes pear shaped (https://en.wikipedia.org/wiki/Pear-shaped).

So.........in summation, check your throttle body out first!!!! Well worth a shot.

With much thanks to all who have contributed either directly or indirectly to me solving this.............thanks guys/gals and shame on GM/Chevy!
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Old May 1st, 2017, 12:48 PM
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did u change the egr valve hose as well? I changed valve only and after 2 weeeks it came on sgain
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Old May 4th, 2017, 8:10 PM
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Originally Posted by Shelley Kostner View Post
did u change the egr valve hose as well? I changed valve only and after 2 weeks it came on sgain
No, didn't need that, just made sure that I also cleaned the gunk off the butterfly valve in the throttle body and it was fine with the EGR valve replacement alone.....

.......but I do know that this is such a random problem (mine was kicking on/off for almost 3 years without any other symptoms/failures despite intensive diagnosis (at a price!) by people who would survive in a tank full of sharks!)... so my advice is clean it up and leave alone..............and if all else seems/looks/feels ok with your Nox then there probably isn't any major problem other than (of course) faulty/crap Chevy OB computers, sorry but true. Best of luck!
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Old May 31st, 2017, 10:49 PM
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Did you ever get it fixed and how/what did you do?
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Old August 24th, 2017, 6:43 AM
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Originally Posted by ruley73 View Post
you'll need to drive it a lot more to see if the egr valve is fixed. I tried to clean the egr valve in ours, but i ended up replacing it because the ses light returned after driving it a while. A new egr valve and gasket (ac-delco p/n 214-2098 + felpro p/n 70804) is only about $75 shipped from rockauto. I replaced it almost 2 years ago and haven't had a problem since. Replacing the egr valve also stopped the service traction control and service stabilitrak warnings from coming on.
omg do any of u guys live in nova scotia canada i need help bad
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Old January 17th, 2019, 1:24 PM
  #97  
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Default p0404 & P0405 after towing small Uhaul trailer.

Hello,

I was recently towing a small Uhaul with my 2007 Equinox and had the Stabilitrak error message come on and codes p0404 and p0405 come on. I replaced the EGR valve and reset the computer and cleared the codes, but the codes appear again. Any idea what step I should take next?

Thanks and blessings,

Jake
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Old January 17th, 2019, 2:33 PM
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Originally Posted by Jake Burton View Post
Hello,

I was recently towing a small Uhaul with my 2007 Equinox and had the Stabilitrak error message come on and codes p0404 and p0405 come on. I replaced the EGR valve and reset the computer and cleared the codes, but the codes appear again. Any idea what step I should take next?

Thanks and blessings,

Jake
My experience suggests it a computer control problem and not the EGR valve itself. I have a sensor (Blue Driver) that allows me to see live data on my cell phone while the car is being driven. I have often had the codes P0404 and P0405 come up with the indication the EGR control values had exceeded their limits which results with the EGR sticking in a fully opened or fully closed position. This would frequently happen to me while driving with the cruise on at speeds of 75 or better for extended periods of time. I just simply cleared the codes and kept on driving. The codes would usually not return until the next time a took a long extended drive. I also took the car to a dealer to have the ECM reprogrammed (spent the diagnostic fee) only to find out that I had the most current updates. You can also try taking the throttle body and EGR valve off the intake manifold and clean out the passages inside the manifold.
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Old January 17th, 2019, 11:38 PM
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Originally Posted by Jake Burton View Post
Hello,

I was recently towing a small Uhaul with my 2007 Equinox and had the Stabilitrak error message come on and codes p0404 and p0405 come on. I replaced the EGR valve and reset the computer and cleared the codes, but the codes appear again. Any idea what step I should take next?

Thanks and blessings,

Jake
I suspect the EGR valve you installed is defective. What brand is the EGR valve you installed?

You can check the wiring and make sure there's no damage. The way the EGR valve's wiring harness is routed from the factory puts a lot of stress on the wires. It comes up from under the air intake hose which requires the wires to make sharp bend to plug into the EGR valve). I have re-routed the pigtail without any modifications so it now goes up and over the throttlebody, then plugs straight into the EGR valve. This alternate wiring path eliminates the sharp bend and doesn't put any stress on the wires. Each vehicle will vary a little bit, but there is just enough extra slack on ours to make this feasible.

I have also suspected for a long time that there is a glitch in the ECM's programming for EGR valve modulation in the 2005-2009 Equinox 3.4L that GM has never addressed. The exact same EGR valve is used in other GM applications with a far lower failure rate. Our Equinox is on it's third EGR valve.
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