So, we bought our 2006 HHR earlier this year, and it was fine for several months before we got the P0010 code. We had a local mechanic replace the two solenoids (intake and exhaust camshaft position), but he was dubious since he said his experience in the past was that the codes would come back.

We got a couple of months of no codes, but earlier this week my husband came home reporting that the CEL was back on and the engine was running rough. Last time. there was no performance issue. He said running rough, "missing," not hard shifting.

So, he put the code reader on and got both codes (last time it was just the P0010 that we pulled, though I guess more came up at the mechanic's).

I erased the codes, started it up, backed it down our long driveway, drove back up, no CEL. Checked for codes, no codes. Drove normally.

So, the question is: why can erasing the codes cause the car to run normally again, and what would that indicate?

We want to dump this car. We bought it used from a private party and it is such a loud car to drive, we should have never gotten it. Worried this is just the beginning of big expenses. It only had around 70,000 miles on it when we bought it.

I think the mechanic said that if the codes came back, he wasn't able to do more, to take it to the dealership mechanic. Hoping to get some insight here.

 

"So, the question is: why can erasing the codes cause the car to run normally again, and what would that indicate?" - erasing the codes, is kinda like a reboot of your home computer. You reboot your computer and everything runs fine, until you encounter that same issue that caused it to act up previously.

A p0010 indicates a fault with the solenoid on the Intake side only (which was previously replaced). P0020 isn't listed in the codes we have available on this site, however a google search turned up this link - P0020 "B" Camshaft Position Actuator Circuit (Bank 2) - DTC Code

To quote: "Basically the check engine light and associated P0020 trouble code means that the voltage in the circuit has fallen below a set limit for a specific amount of time (varies by make/model/engine). ".

A single problem can often generate two or more codes - and that is where a GM dealer with their super-code readers, and diagnostic procedures, can often pinpoint a problem that a non-GM shop cannot.

With that said, I'd inspect the wiring harness to the solenoids that were replaced, and verify that the connectors to the top of the solenoids are not damaged (cause they are tricky to disconnect and a member or two here have damaged them), and that the wiring harness for them is ok as well, and not pinched somewhere under the air filter housing.

Not sure what you mean by loud car - engine noise? Road noise?

It only has 70,000+ miles on it, but don't forget that it is now 9 years old - if the previous owner neglected some of the routine maintenance, it should be not that difficult to bring back up to snuff without spending major $'s.

 

"So, the question is: why can erasing the codes cause the car to run normally again, and what would that indicate?"

Because the presence of some codes causes the computer to change it's actions.

Dump the car! You hate it, no use owning it.

 

Welcome to the site! Sorry the HHR isn't up to par.

 

D'oh, I meant to put P0010/0011

 

ahhh - well as you are already aware, the p0010/11 codes point to the INTAKE actuator solenoid being at fault. If double checking the connector at the top of it looks ok, then the solenoid itself is suspected faulty, either through it's internal electrical circuit (should measure out at 12 ohms if I remember correctly), or is contaminated by dirty oil (typically caused by neglected oil changes) .

If you end up replacing it, I'd suggest doing an oil and filter change at the same time, and make sure to use a genuine GM replacement part. The aftermarket ones may or may not meet the latest GM part revision.