Limp Home 3 Minutes After Hot Restart

**EndressAuto** · August 17, 2015, 07:12 AM

Just like the title says, the car gets limp home mode with no throttle actuation after 3 minutes of driving after a hot restart (getting gas, stopping for a drink...). This is when it tests the throttle, intake 1, and intake 2 models to what the engine is actually doing. It sees that something is skewed and puts the car into limp home mode. Kind of dumb and dangerous. Let the car sit for 5 minutes for the "timer" to run out and its good to go for the rest of the ride.

First time it had codes:
- P0101 Mass Air Flow Signal Out Of Range
- P0102 Maas Air Flow Signal Low
- P0103 Mass Air Flow Signal High
- P0503 Vehicle Speed Sensor Intermittently High Signal
- P1182 Supercharger Inlet Pressure Sensor Range

Cleared and took car for a few test drives. P0101 came back. Swapped out the MAF with a known good unit i had, no change. Checked freeze frame and it all looked normal when compared to specs and when the car is running fine. Found the boost pressure sensor coated in oil which i cleaned and took the car for multiple test drives. All was fine and went onto dealing with a shifting issue. Gave the car back and 2 days later, same issue. Have the car back now and codes P0101 and P1182 are stored. Boost pressure sensor is fine so i think it was just a coincidence that it "fixed" the problem.

Ive checked for vacuum leaks, none, checked for boost leaks which i found and fixed two very very minor leaks. Checked throttle actuation, fully closes and fully opens. Im just about out of ideas here. Throttle body malfunction could happen when heat soaked, but at least one of the two position sensors should see that.

**McFred** · August 17, 2015, 07:29 AM

So... Ecotec? At least it doesn't sound like a Honda which to the best of my knowledge are all MAP, not MAF.

Maybe look up the code-canceling procedure and try from scratch? Sorry, I'm GM-ignorant.

**EndressAuto** · August 17, 2015, 07:40 AM

Yes Ecotec. The diagnostic procedure leads nowhere as i've done it twice over now. Leads to "intermittent problem"....yea, we get that. Haha. But what is the problem.

On a side note, are these motors from Cobalts or Saab's? The mount for the cam position sensor says Saab on it? Or maybe they just use the same engines and swap parts around.

**MadMaxAtom** · August 17, 2015, 08:12 AM

Engines/injectors/sensors and management electrics are all GM. Can you access the data stream and see the the values for the specific trouble code tagged input devices? If so,what are the values?

**EndressAuto** · August 17, 2015, 08:29 AM

Do you want actual or freezeframe?

**MadMaxAtom** · August 17, 2015, 08:38 AM

Freeze frame should show you why the codes are being set: The values should be out of range. The MAF codes can be caused by oil on the wire/sensor. However,the VSS is not related at all to the MAF. The VSS is mounted in the top of diff section of the transaxle. Never seen one go bad. Are your battery voltages within range,and battery fully charged with no weak cells?

**EndressAuto** · August 17, 2015, 10:14 AM

Freeze frame is all showing what it should be when compared to spec and normal running engine. I already swapped out the MAF with a known good unit right off the bat and no change.

Im not too concerned about the VSS fault as it only popped up once and hasnt come back.

Battery and charging system is all fine. Checked all grounds that i could find but if someone could give me a list of where they are located on this car ill check them all.

**bolus** · August 17, 2015, 10:13 PM

one ground is by the battery and another on the front of the engine near the oil filter I believe.

Im no mechanic, but from seeing weird issues over the years on these forums I'd say check the fuses. Blow fuses have caused some of the weirdest problems in these cars that made no sense.

Is the MAF sensor in the smooth intake or does it look like corrugated hose (the very old original intake that caused issues)? My corrugated intake had a hole in it and I replaced it with the smooth plastic intake.

**silver** · August 21, 2015, 05:52 AM

I agree with Bolus that electrical issues cause the weirdest problems....so my question is, is there anything non-factory on the electrical system, like different radiator fan or anything?

also, make sure the throttle body plug is fully seated, a bunch of atoms were built and they forgot to install the retainer clip, mine fell out while driving which resulted in the car staying at idle but having absolutely no throttle input, sounds different then what your describing so I wouldn't think yours has fallen out but it could be loose.

**Terry Kennedy** · August 21, 2015, 01:10 PM

Originally Posted by silver

also, make sure the throttle body plug is fully seated, a bunch of atoms were built and they forgot to install the retainer clip, mine fell out while driving which resulted in the car staying at idle but having absolutely no throttle input, sounds different then what your describing so I wouldn't think yours has fallen out but it could be loose.

You can normally detect this by listening for the "burp" when the PCM cycles it at ignition on time. It is a different sound and a different location from the fizzing of the fuel pump.