Uluz2a6

I restore Ecotec engines for side income here in Las Vegas and am truly a fan of these power plants. To date I have rebuilt just under 100 total between the 2.2 and 2.4 models. I consider myself average intelligence and have no problem admitting fault when I screw up (which I do). I am pleading ignorance and am open to any advice for the following issue listed below. Thank you in advance for looking.

2008 2.2 Cobalt

Fresh engine rebuild.

I was given the core and the engine was installed by owners friends. Car is now in my possession due to a no start complaint.

First resolved issue was no positive wire from battery to starter. It had been tucked out of the way. After correcting, the car fired right up.

P0335 code and "service traction control" scrolling on info center under gauges

The issue remaining is no RPM signal to tachometer. Not only is that annoying, but I cannot perform the CASE relearn (reprogram crankshaft position sensor). I removed the harness and have 5 volts on outer wires and solid ground on center wire. There is an intermediary harness between main harness and sensor. I have the same signals before and after it, so theoretically its not at fault. Upon removing the sensor and inspecting it, I see that the center "prong" was crushed and lying across at least one of the other prongs. Evidently it was forced down when plugged in. I purchased a new sensor (GM OEM from dealership) and reinstalled. Same issue present. No fuses blown. No visible damage to wiring harness and I have spent a lot of time inspecting it.

Using my Tech 2 (authentic not a clone) I cannot complete the relearn process because the step "place foot on brake pedal and hold, start car" is performed but the screen flashes start and idle car. Clearly the ECM doesn't know its running.

Or does it? Going into engine data on Tech 2 I have no RPM. However if I going to ignition data I have RPM signal from the CPK. uuummmm? What is going on?

I have inspected the installed engine and put grounds back into correct locations as well as determining everything else is plugged in as should be.

So my question to you learned people in the Ecotec world is: How can the CPK register RPM at ignition data control and not at engine? I know it could have damaged electronics by not having positive cable connected, but is it likely? If I still have voltage and ground at sensor, is it likely that the bent prong did not damage ECM?

When I say it runs, I mean it runs well . Idle is smooth. Test drive was also good. power seems to be as desired. Cranks longer than it should, but I assume that is a result of this issue. I see that issue often until I perform the relearn, then starts much faster (as intended).

I almost wish it wasn't running so well, then maybe I could be provided a hint from the symptoms.

Sharkey

iTrader: (1)

the code, long cranking, it points to no crank signal. the engine will run off the cam position sensor, but only after the computer recognises the crank sensor isnt working and sets the code during that ignition cycle, this is why it cranks for a while before it starts. i would say the ckp signal on the scanner is false data, ive seen that happen from time to time. depending on the way the pcm firmware is written it can use the cam sensor signal and make up rpm data for the crank signal, and thats what the pcm uses for a crank signal so it will run.

have you actually put a scope on the crank sensor and viewed exactly what its doing? you didnt by chance change the crankshaft during rebuild did you? or sent the crank for machining? im sure your aware, but the 02-06 2.2l use a cast in 7x reluctor wheel, and the 07+ uses a 58x bolt on wheel. if you have the wrong setup it will cause the issue.

Uluz2a6

I am certain the crankshaft /reluctor wheel is correct. I do not have a scope to watch crank sensor. Despite all my rebuilds, I am a small setup. I work out of a 3 stall garage at home. Real issues like this are rare for me. My issues are straightforward like rod knock, hole in the block, jumped timing, blown out rear main seals, etc. Mechanical repairs.

The long crank does scream no crank sensor signal, I agree.

The Tech 2 is getting a signal from the CPK when it accesses it from another direction though. I am certain of this because it shows the CPK as the source in addition to the camshaft sensor reference. The system has 2 5 volt systems to operate together. That way if on of the systems has a fatal flaw (like this) the car can still be operated and not strand the owner.

I have decided to make an appointment with an auto electric shop for Monday if I cannot resolve by then.

One other update I can offer is the MIL is taking longer to set than before. On an idle situation, it can take up to 15 minutes to set. Driving can take almost as long.

bhshoot

Any feed back on this question? I am having the same issue.