rcchevrolet

2008 Equinox 3.4L LTZ
Have a P1779 from my BlueDriver OBD2 reader, see the image attached, reporting that the most common fix is to replace the EGR pipe.
Wondering if there is a good way to clean the pipe of its carbon deposits instead of replacing it.
Any and all ideas are welcome.

ruley73

A bad EGR valve with the 3.4L engine in the Equinox/Torrent usually causes Stabilitrak to be disabled and triggers DTCs P0404 (or sometimes P0405), P0561, and P1779. I'm certain the pipe is squeaky clean. They never clog up if the engine is well maintained. Replace the EGR valve. I've needed to replace mine twice in the 15 years we've owned it. I was getting the same group of codes, and replacing the EGR valve fixed it both times.

I replaced the EGR pipe once, but not because it was clogged. One of the ribs at the top bend cracked while replacing the EGR valve the second time. You'll know if yours does this because it sounds like a nasty exhaust leak.

rcchevrolet

There is no check engine light displayed, the DTC P1779 showed up when the newly acquired OBD2 reader was asked to do a total scan of all sensors. I have recently noticed the Stabilitrack light, next to the shifter, turning on and off but with no noticeable bad symptoms which I have ignored. About two years ago I replaced the EGR valve due to those DTC codes you mentioned coming up.
I do my own repair and maintenance meticulously since I purchased it on 6/15/2015. Very reliable SUV, except for its engine oil consumption of about 1qt every 900-1000 miles, without any symptoms of the PCV valve being stuck or oil burning, etc. I have tried using brake cleaner on both PCV pipes, driving a few times, and changing the oil and filter. Will do it once again at the next oil change.
Thank you so much for your reply.

ruley73

If you're only getting P1779 alone, I would not replace the EGR valve. I really wouldn't worry about it and I'll explain why. Your Equinox may be doing the same thing mine does.

The code definition for P1779 for this vehicle as stated in GM's service information is "The TCM detects that the engine air flow torque steady state signal to the ECM is invalid." The action taken when the DTC sets is "The TCM will default driver requested torque data to 300 Nm (221 lb ft)." In layman's terms, the TCM doesn't trust the signal it's getting from the ECM, so it defaults to a predetermined data point (which is slightly higher than the range it would typically see from the ECM - the 3.4L engine is rated for 210 lb ft of torque) as a failsafe to maintain functionality. The P1779 DTC just documents what happened and nothing more. Stabilitrak being disabled is simply the result of the that code being stored. P1779 is a type C DTC so it doesn't trigger the check engine light. Unlike most other DTCs, there isn't diagnostic process specified so no action can really be taken.

I believe there's simply a bug in the software that is causing this. Our Equinox has done this the whole time we've owned it: If you floor the gas pedal and don't let up, SERVICE STABILITRAK and SERVICE TRACTION CONTROL messages are displayed when you accelerate past about 87-90 MPH. The system resets itself within a couple key cycles and remains trouble free until the next time the same scenario plays out. Only Stabilitrak is disabled while the messages are displayed - the traction control still functions fine despite the message implying it won't. I've just lived with it because it's not often I go that fast anyways. A new computer calibration may be available that might fix this, but I'm not willing to pay a dealership to find out for such a trivial problem. I haven't found any TSBs that mention this issue either.

rcchevrolet

Wow! Thank you so much for taking the time to educate me so thoroughly, This engine works so quietly and evenly that I don't fail to appreciate it often. In truth, this car is a rebuilt title which I knew to be a gamble but it fit the need. It has a clean appearance in and out with three different shades of white, and that's fine with my wife also. It has lasted longer than I expected and will not replace it if it keeps up. The worse problem has been extensive undercarriage rust almost everywhere; have sprayed and sprayed all of it, time and again with great results. No dangerous rust to critical components just the thin sheet metal parts.
Have a great day!

ruley73

How many miles are on yours? I completely agree these are very reliable vehicles if properly maintained. The places you want to inspect most closely for rust are the front subframe bolts on either side of the radiator support. Mine are already very rusty. I'll be happy if it lasts 2 more years assuming I keep it that long in the first place. We only paid $13,500 for it back in 2008, so it doesn't owe us a dime.

I just had the cylinder heads and gaskets replaced last month at 214K miles which cost me about $1700. A lot of people thought I was crazy, but with vehicle prices the way they are right now I was willing to splurge to buy me some time to search for something to replace it and hope used car prices come down a bit. There really isn't anything affordable and reliable that's comparable to this Equinox so I'm having a hard time finding something I want. Everything is either too big or too small, doesn't have enough power, or has a powertrain that's known to be problematic.

The engine was still running fine and never overheated, but the lower intake gaskets and head gaskets both had external coolant leaks. The cooling system was also building up too much pressure. The heads may have been fine, but I wasn't willing to risk it. Local machine shops wanted $300-$400 just to inspect & clean them up, and I would have needed to buy new heads in addition to that if they were bad anyways. So, I instead bought a pair of remanufactured heads from AutoZone for only $470 with a coupon. Yours will likely succumb to the same failures with time. The head gasket design is still the old school graphite type because the basic design of this engine is over 40 years old. Newer engines have much better multi-layer steel head gaskets that don't rot away with age/wear like these do.

rcchevrolet

"How many miles are on yours? I completely agree these are very reliable vehicles if properly maintained. The places you want to inspect most closely for rust are the front subframe bolts on either side of the radiator support. Mine are already very rusty. I'll be happy if it lasts 2 more years assuming I keep it that long in the first place. We only paid $13,500 for it back in 2008, so it doesn't owe us a dime."How many miles are on yours? I completely agree these are very reliable vehicles if properly maintained. The places you want to inspect most closely for rust are the front subframe bolts on either side of the radiator support. Mine are already very rusty. I'll be happy if it lasts 2 more years assuming I keep it that long in the first place. We only paid $13,500 for it back in 2008, so it doesn't owe us a dime.
Mine now has 116k miles purchased in 6/15/15, 58,800 miles, for around $7,000 as a rebuilt title. Lots of rust also and some places near crucial areas, I believe, and in the same front, sub-frame bolts area. About 2 yrs ago I commented my concern about this particular area and said not to worry about it the bolts are very strong and will hold. Go figure. I have really sprayed with Rust-Oleum black enamel spray and keep spraying from time to time. In addition I bought a couple of can of this anti-rust for all the hollow areas and hope it has helped. From Amazon:

Amazon

Amazon

No engine problems except for the high oil consumption that I mentioned before. Have changed fluids on the auto transmission as well as transfer case and differential, twice already. I tow a small pop up camper suv (2800lbs) about 5 times a yea,r and also have installed an extra auto transmission fluid cooler to protect the A/T. In addition, upon purchase, I also flushed the radiator 4-5 times (until fluid was tally clear), plus change it every 2 yrs. This had the effect of lowering the engine temperature gauge reading from exactly middle range to a little a noticeable little less. Just changed the 5 yr coolant and the temperature needle is even a little lower.
I have the same problem of not knowing when or for what suv I wil be buying as a replacement. The automobile industry went crazy with their ridiculously inflated prices. I am considering only a 6 cylinder,non turbo, with traditional shifting transmission. So far I have been looking at Toyota Highlander with about 100,000 miles with manufacturer’s warranty, but really not sure at all.

I am watching this channel in youtube, they seem serious and real and gives me hope:

You Tube

Here are a couple pictures of what the subframe bolts, driver side, look like and very rusted but totally covered in paint:

rcchevrolet

ruley73:
The correct cavity rust treatment spray with the long sprayer tube is: My Equinox is not all that perfect, the paint has various problems including rust "freckles" showing through the paint; the worst was the hood which cost me $300 to paint and not a very good job at that. Also has three shades of white in different panels. Overall the car is decent so we are happy with it.