donbrew

Because hydraulic thing can operate fine, until they don't and it has to be 10 degrees off, under the correct condition (see above), to throw the code. That's why I suggested the VVT valves or the actuators. The valves theoretically have their own set of codes, but the actuators don't. However, valves have been known to not throw a code just cause the Traction Control light.

So my theory is: since you are sure the chain is right and the tensioner is right and the valves are reacting to signals right it must be an actuator.

uluz2a6

So I removed the timing chain and counted/verified the links were correctly marked. They were. I replaced both the intake and exhaust camshaft position sensors. Performed the CASE learn procedure successfully and it still runs well. MIL still present after couple days. No reduced power though.

Convinced myself it must be an incorrect reluctor wheel on crankshaft. Removed the engine and disassembled it. All was perfect on internals including the correct reluctor wheel. FYI the other wheel for those crankshafts is physically larger and the #4 piston cannot clear it. (point being cannot install incorrect part).

Reassembled and fired it up without issue. Instantly set MIL It was requesting another case learn procedure. When I attempted to perform it this time I ran into a problem At the step to apply and hold brake pedal and start engine then press enter, it merely flashes start and idle engine. This means that the ECM doesn't know the engine is running. I noticed the tachometer doesn't work nor does the Tech 2 show RPM. The owner claims the tachometer never worked. When the key is turned to initially to start the engine the tachometer DOES work until engine fires then stops again.

Now I am wondering if this is an ECM issue. Any thoughts?

donbrew

Make sure you didn't blow the cig lighter fuse, it also supplies the OBD port.

I guess you just are not going to suspect a VVT valve. Which leaves the actuators.

uluz2a6

Well the Tech 2 powers up correctly so I assume the power source is not the issue The ECM clearly is unaware the engine is running.

donbrew

If the ECM is unaware of the engine running how do you suppose the signals to fire are getting to the coils and injectors?

uluz2a6

That was my point when posting this for help. I am open to any suggestions. I'm at a complete loss.

uluz2a6

So the intake and exhaust camshafts have identical markings yet local dealership parts department confirms that they are not the

uluz2a6

So my question is how am I to tell if the machine shop that reconditioned the head put cams on correctly? If they are reversed I guess that cod be the issue between crankshaft position sensor and camshaft position sensor

donbrew

GMpartsdirect.com says they are the same part across all 2008 2.0,2.2 & 2.4. Earlier models of Cobalt,G6 etc had a drive gear for power steering on the intake.

It is possible these are installed incorrectly.

uluz2a6

Not the gears, the actual cam shafts.
Intake 12578511
Exhaust 12578512