Soofisahab

iTrader: (2)

Hi,

I'm in Houston visiting my mom and my '08 Cobalt SS is acting strange. Getting codes p2227, p0299, BPV is erratic, in limp mode, etc. Engine was rebuilt 1000 miles ago and has been acting funny ever since the rebuild. I'm convinced the ecu/pcm is bad at this point as I've tried everything else. If you have a spare ecu/pcm in Houston area or know of someone who does, please reply/pm. Thanks!

Mods: I posted in Regional forum as well, please leave up as I need as many eyes on this as I can get, thanks!

SSlobalt

EDIT: Sorry, I just searched for the code and found the thread you're talking about where Tom at CED found that the ECM was bad.


What is your vac reading at idle? It should be around 19-20. This sounds like a vac leak, but could also be that your wastegate is stuck open. Did you replace the turbo along with the motor? Check the wastegate controls, like the vac solenoid/connector and all related hoses. Check the wastegate rod and make sure it didn't come out of the arm, and make sure the lock nut is still tight. Vac test the wastegate actuator if you have a Mighty Vac Hand pump.

Also, if you have the stock coldside pipe, can you check the vac line where it connects to the barb on the coldside pipe? That thing likes to break. It's right by the TMAP sensor.

The Barmoetric Pressure code is a bit of a mystery on here. Some think it's set by the ECU and that there is no actual sensor. In the Chevy diesel world, the sensor is located within the EGR system. I haven't been able to find out if ours is the same.


Pic of wastegate actuator, solenoid, hoses:

Soofisahab

iTrader: (2)

Yes, the turbo was replaced along with head and piston #4.

The vaccum is 19-20 at idle.

The car ran funny from the moment I got it back, but I attributed that to the gms1 maps on the stock tune (was reset to stock tune by dealership). I uploaded my trifecta tune that has the adjustment for gms1 sensors and it ran great for a three gear pull then things went south.

I assumed it was the sensors so I cleaned the MAF and MAP sensors with MAF cleaner to no effect. I switched the maps and observed performance through torque on my phone and both were consistent with the mechanical boost gauge.

The next day I hit the road to drive to my mom in Texas and the car would boost no higher than 5-10 psi if I gave 75-80% throttle for brief intervals; if I went full throttle for long intervals, it would completely cut boost to 2 psi limp mode (would have to shut car off and restart to get 5-10 psi limp mode again).

The BPV functions seldomly for multiple consecutive pressure releases, then it stops and I hear compressor flutter from the air going back into the blades. I haven't heard the BPV work properly for a while now.

The car backfires 1-2 times when pulling through a gear. If I pull through a gear and let off quickly before redline, it will pop 1-2 seconds after I let off.

Another strange thing I noticed is that my torque app doesn't clear codes as easily as it did before the rebuild(via elm327 obd 2 bluetooth adapter).


I was initially getting code p2227 Barometric sensor range/performance, then I sent a datalog to Trifecta and he sent me an updated tune. Uploaded the tune and now I have a pending fault for code p0299 turbo underboost.

I gave a visual inspection to the vaccum lines, but did not go through them thoroughly. Definitely worth a try as this may very well be a vaccum leak. Do you have a vaccum diagram of all the vaccum lines?

The reason I'm thnking it's the ecu/pcm is the car ran fine for a very brief moment. What confuses me is that it ran like crap when I got it back, then ran great briefly for three gears, then it has gone to crap ever since. Do you think it's ecu/pcm?

SSlobalt

Reading some of the other threads, it definitely could be the ECM. If you're at 19-20 at idle, you probably don't have a vac leak. Maybe someone in the Houston area will have an ECM, but you might wanna just go ahead and buy one from the Classifieds or ZZP.

ei3dag3

iTrader: (5)

p0299 underboost is going to be a vacuum/boost leak somewhere.
i wouldn't worry too much about the vacuum hose diagrams as they are set up correctly from stock.
better yet if you could just send us a picture of your setup we/I can tell you if its mapped correctly.
check the piping like sslobalt. when you get home you will NEED to do a boost leak check.
99% of the time you get that code when you have a leak. i've had this code before.

ei3dag3

iTrader: (5)

you can still have a vacuum of 19-20 at idle and still have a boost leak that causes the underboost code.

OP do not buy an ECM. If your car starts and runs there is nothing wrong with it.
If you'd really like to confirm this tell Vince to send you an "ECP" Tune.
My bets is that your car will run just fine. That is only a band aid and you MUST fix all leaks.

Soofisahab

iTrader: (2)

I ask for a diagram as the engine was recently rebuilt and the tech may have routed incorrectly. Also, some of those vac lines disappear into the abyss under the intake mani and will be hard to get pictures. I'm thinking of going to auto parts store an running all new lines.

Please supply diagram if possible.

Thanks again.

ei3dag3

iTrader: (5)

theres only one line that goes down below the engine and thats the one that goes to the cold side.
i'd gladly take a picture for you however i'm at work and my car is at home.
text me man
9034134644
send me pictures and ill tell you if its right.

FasterIsBetter

He's talking about the vac canister lines. They lead below the intake mani as well.

SSlobalt

The vac tank is a good thing to check. It's under the intake manifold and is hard to get to, but you can see if better from underneath the car. You have the vac tank source tube coming from the center of the intake manifold and going to the vac tank source port on the left of the tank, when facing the front of the car. You also have a vac tank outlet tube going to the vac solenoid on the manifold. Basically, vac is supplied to the tank from that tube in the center of the manifold and is stored there until the vac solenoid opens and delivers vac to the BPV. When the solenoid is open the other way, it supplies boost pressure to the BPV, via the coldside piping tube. This holds the BPV closed when you're under boost.

The vac tanks have been known to crack. You can bypass it to test if your tank is leaking. When bypassed, if your car runs correctly, you know the tank is leaking.





You can see the boost pressure supply tube next to the GMS1 MAP sensor.