I have owned a 2009 Cobalt SS for a week now and am trying to track down the issue(s), that are causing the following codes:

P2178 Fuel system rich at cruise or accel (this code has sometimes come twice at a time)
P0299 Engine under boost (this code has sometimes come twice at a time)
P ---- Minimum throttle position unknown or something like that. Sorry I did not get the exact code number.

During the first few times of driving, I wound it all the way out in 3 or 4th gear, it would get to higher RPMs (4-5K+) and cut boost and enter low power mode until the car was cycled off/on again. The throttle position code does not always appear, however, the rich fuel and under boost always accompany this happening. After learning this was a consistent reaction I have refrained from pushing it hard to redline. If I upshift early the car makes about 12psi with no issues. If I maintain part throttle, it will rev all the way to 6k without issues. It does seem underpowered, though, I can't really say having only ever driven one other turbocharged cobalt, which made much more boost.

I have performed a boost leak test. Yet, I am not convinced it was super effective since I did it alone and did not have a locking chuck so I could not pressurize and look/listen for leaks at the same time. Though I had the regulator set up around 30 psi and didn't hear anything obvious except some hissing from the valve cover oil fill (if I blocked that off I would get a farting noise from the PCV line going to the airbox, which was disconnected for the test). All that to say, I'd think If I had a leak I would've heard it at 30+ psi, but idk.

Another observation: I currently have access to a OBDii scanner that can get live data from the PCM. The TPS (throttle position sensor) value will max out at only 83.9%, and rests around 20%. With the engine off, but the ignition on I can work the pedal and get data appearing on the graph. Rests steady at 20%, then sharp jump to 83.9% with the pedal floored, then back to 20% when letting off the pedal. sHoULdn'T iT Go tO oNe HunDRed?? Or is this limited range normal? It will max at 83.9% while driving too.

Third Observation: Blue smoke escapes from the exhaust after mod-heavy throttle, usually more than 5psi. I am currently looking for either rebuild kits or entire replacement cartridges (CHRA) for the K04 as I would like it to stop smoking and am fairly certain it is due to bad seals. But need to not spend several hundred dollars on the car again, so quickly. I do not think this is the cause of the low boost or rich condition, though maybe some of you will have different ideas.

Basic engine info: 127K LNF with factory Turbo and IC. Stock except: K&N drop-in filter, ZZP upgraded intake tube, Injen hot side piping, Modern Performance full 3" exhaust. I have no idea about the state of PCM or possible tunes. The car behaves the same whether or not the cruise control or ESC is on/off.

Please help as best you can/are willing.

 

The Plot thickens after some more testing on the road today.

- I was able to make one or two pulls to redline at WOT without issues.
- I did get the car into Low power mode a few times. Each time it was WOT, 3rd or 4th gear, pulling hard until 4500rpm, then it would kill power and not allow any positive manifold pressure. It did not throw the rich or under boost code each time, it was mix-matched, sometimes one, sometimes both. For one occurrence it did not make any codes, just went into low-power mode. The low-power mode will remain until the car is cycled on/off. Codes will remain until they are cleared, and they do not affect the boost level or any other drivability of the car.
- I believe that it could be a boost leak still, it is just strange how the symptoms are not consistent like I think they would be with a mechanical problem like that.

Thoughts?

 

Took the front bumper off this morning and discovered a tear in the IC coupling on the hot side. So it seems at least for now that my IC is not cracked.

 

Replaced the torn silicon coupling and the car really came alive. Makes about 21-22 psi at WOT. Didn't last long though, it went into low power mode again during one pull and had another engine under boost code. Now it only makes about 17 psi.

I have some more couplers on the way since I am not sure about the age of the others on the car. I will also buy a locking valve stem chuck so I can perform a boost leak test more effectively.

All of the vacuum lines look and feel very nice, so I don't suspect it is those.

 

I have not redone the boost leak test yet, however, I discovered an easter egg which is contrary to what I said before.

With that other huge leak fixed, the car does make different boost numbers with the Cruise control On vs Off.
- On it will make 12-15 psi
- Off makes over 17-20+ psi (it seems pretty inconsistent in it precise MAP target)

I have left it on mostly since discovering this, even after several WOT pulls through 2nd, 3rd, and 4th, the car does not enter low power mode or produce any codes. So...... I'm thinking:
- could it still be a physical boost leak that is only vulnerable to higher psi levels?
- or could it be due to other things like a sensor malfunction (stock MAP sensors installed)
- or the fact that this tune was flashed for a different intercooler and intake that are no longer installed?

Also, I have contacted Trifecta asking about the car's VIN in their records for a tune and they said they have none. Though they are the only place I have read that offers that on/off switch with the cruise control button. Anyone have any wisdom on how to confirm what my PCM is? Mostly I am thinking about future fiddling and if it is locked from Trifecta, I would like to know in advance so I can make plans to get around that.

 

Sorry for my short story. I am moving the thread here as I believe I posted in the wrong forum first. Below are all the replies so far (only me ) and strike-throughs on what is answered/not needed.

I have owned a 2009 Cobalt SS for a week (month) now and am trying to track down the issue(s), that are causing the following codes:

P2178 Fuel system rich at cruise or accel (this code has sometimes come twice at a time)
P0299 Engine under boost (this code has sometimes come twice at a time)
P ---- Minimum throttle position unknown or something like that. Sorry I did not get the exact code number.

During the first few times of driving, I wound it all the way out in 3 or 4th gear, it would get to higher RPMs (4-5K+) and cut boost and enter low power mode until the car was cycled off/on again. The throttle position code does not always appear, however, the rich fuel and under boost always accompany this happening. After learning this was a consistent reaction I have refrained from pushing it hard to redline. If I upshift early the car makes about 12psi with no issues. If I maintain part throttle, it will rev all the way to 6k without issues. It does seem underpowered, though, I can't really say having only ever driven one other turbocharged cobalt, which made much more boost.

I have performed a boost leak test. Yet, I am not convinced it was super effective since I did it alone and did not have a locking chuck so I could not pressurize and look/listen for leaks at the same time. Though I had the regulator set up around 30 psi and didn't hear anything obvious except some hissing from the valve cover oil fill (if I blocked that off I would get a farting noise from the PCV line going to the airbox, which was disconnected for the test). All that to say, I'd think If I had a leak I would've heard it at 30+ psi, but idk.

Another observation: I currently have access to a OBDii scanner that can get live data from the PCM. The TPS (throttle position sensor) value will max out at only 83.9%, and rests around 20%. With the engine off, but the ignition on I can work the pedal and get data appearing on the graph. Rests steady at 20%, then sharp jump to 83.9% with the pedal floored, then back to 20% when letting off the pedal. sHoULdn'T iT Go tO oNe HunDRed?? Or is this limited range normal? It will max at 83.9% while driving too. < I learned that 20-80% is normal

Third Observation: Blue smoke escapes from the exhaust after mod-heavy throttle, usually more than 5psi. I am currently looking for either rebuild kits or entire replacement cartridges (CHRA) for the K04 as I would like it to stop smoking and am fairly certain it is due to bad seals. But need to not spend several hundred dollars on the car again, so quickly. I do not think this is the cause of the low boost or rich condition, though maybe some of you will have different ideas.

Basic engine info: 127K LNF with factory Turbo and IC. Stock except: K&N drop-in filter, ZZP upgraded intake tube, Injen hot side piping, Modern Performance full 3" exhaust. I have no idea about the state of PCM or possible tunes. The car behaves the same whether or not the cruise control or ESC is on/off. < Not true, after I fixed boost leak I discovered a switchable tune with the Cruise Control

Please help as best you can/are willing.
__________________________________________________ __________________________________________________ __________________________________________________ _________

The Plot thickens after some more testing on the road today.

- I was able to make one or two pulls to redline at WOT without issues.
- I did get the car into Low power mode a few times. Each time it was WOT, 3rd or 4th gear, pulling hard until 4500rpm, then it would kill power and not allow any positive manifold pressure. It did not throw the rich or under boost code each time, it was mix-matched, sometimes one, sometimes both. For one occurrence it did not make any codes, just went into low-power mode. The low-power mode will remain until the car is cycled on/off. Codes will remain until they are cleared, and they do not affect the boost level or any other drivability of the car.
- I believe that it could be a boost leak still, it is just strange how the symptoms are not consistent like I think they would be with a mechanical problem like that. < Leak found below
__________________________________________________ __________________________________________________ __________________________________________________ _________

Took the front bumper off this morning and discovered a tear in the IC coupling on the hot side. So it seems at least for now that my IC is not cracked.
__________________________________________________ __________________________________________________ __________________________________________________ _________
Replaced the torn silicon coupling and the car really came alive. Makes about 21-22 psi at WOT. Didn't last long though, it went into low power mode again during one pull and had another engine under boost code. Now it only makes about 17 psi.

I have some more couplers on the way since I am not sure about the age of the others on the car. I will also buy a locking valve stem chuck so I can perform a boost leak test more effectively.

All of the vacuum lines look and feel very nice, so I don't suspect it is those.
__________________________________________________ __________________________________________________ __________________________________________________ _________
I have not redone the boost leak test yet, however, I discovered an easter egg which is contrary to what I said before.

With that other huge leak fixed, the car does have a switchable tune with Cruise control On vs Off.
- On it will make 12-15 psi
- Off makes over 17-20+ psi (it seems pretty inconsistent in it precise MAP target, I guess this is due to the way the PCM manages torque via Desired Air Loads?)

I have left it on mostly since discovering this, even after several WOT pulls through 2nd, 3rd, and 4th, the car does not enter low power mode or produce any codes. So...... I'm thinking:
- could it still be a physical boost leak that is only vulnerable to higher psi levels?
- or could it be due to other things like a sensor malfunction not working well at higher psi? (stock MAP sensors installed)
- or the fact that this tune was flashed for a different intercooler and intake that are no longer installed?

Also, I have contacted Trifecta asking about the car's VIN in their records for a tune and they said they have none. Though they are the only place I have read that offers that on/off switch with the cruise control button. Anyone have any wisdom on how to confirm what my PCM is? Mostly I am thinking about future fiddling and if it is locked from Trifecta, I would like to know in advance so I can make plans to get around that.

 

Problem solved.

I was misled by the timing of
1. me touching up a silicone coupler (adjusted the two pipes top give the coupler more bite and tightened the clamps)
2. discovering the switchable tune

The coupler was (must have been) causing the boost leak, but I discovered the tune pretty much the next time I drove the car.

I was able to confirm this recently after doing several pulls 2-4th gear both with and without the tune on. No problems and no codes. Have been driving it without issue for the last 2 weeks or so.

Now I just need to get the turbo seals fixed and the PCV system looked at.

 

Problem solved in this thread:

https://www.cobaltss.net/forums/prob...oblems-330740/