Hi all.

Have an 08 Cobalt that started acting up about 3 months ago that we've slowly been trying to troubleshoot and replace parts on, main problem is 0-4 lbs of boost under WOT.

Mods:
-3 inch catless DP
-Injen intake w/ cone filter
-Custom street tune anywhere from 21-27 psi depending on conditions

Original problems:
-p0243
-p0036
-p0300
-p0304

Originally tried:
-pulling vacuum line off of wastegate to see if we could build any boost on spring pressure without interference from the BCS
-changed spark plugs
-pulled intake/intercooler/all piping checked for tears and scrubbed everything clean
-checked CBV diaphragm, no visible tears or pinholes
-soaked valves in GM top end cleaner and removed all buildup
-used sensor safe cleaner to remove grime and oil residue from all sensors including MAP and MAF
-replaced Boost Control Solenoid on turbo, replaced EVAP sensor on manifold, and I believe it's the temp sensor? in the lower IC piping on the passenger side
-replaced rear 02 sensor since the simulator elbow came loose and dragged harness on the ground and 02 fell out
-adjusted wastegate arm
-reset computer multiple times, removed ECU from clips and waited about 10-15 min

Now we're down to:
-p2178
-p0243
-no boost

CEL scanner shows Bank 1 too rich and I think Turbocharger Wastegate Solenoid malfunction, still lost and very frustrated with the car at this point. Really just trying to get the car making boost again so we can sell and move on to something else, any help is greatly appreciated!

 

Check the electrical connector for the wastegate, make sure one of the wires hasn't pull out.

There is only one thread with that wastegate code and he had a bad connector.

 

It seemed fine when I unclipped it from the old sensor, I can pull the rubber boot back and check after work.

 

I have the same year car and I'm having the exact same problem. Did you ever fix yours? And if so what was the problem?

 

Check the connector to the wastegate solenoid for the backed out wire like mentioned above. I had this problem after installing my ZFR the one wire backed out. Also check to make sure one of the wires didnt break cause that can happen as well.