About a week ago I got a code P0030 and a P00135 on my 2006 HHR LS 2.2 with 270,000 miles. My understanding was that both of these related to the upstream O2 sensor, so I checked the flex pipe (it was good), then replaced the sensor with a Denso direct-fit unit. Cleared the codes and started it up, no CEL. Drove for a bit, turned it off and back on again, and then the CEL was back on. Thought "huh, maybe it's best to swap out the downstream as well" so I did. Then the same thing happened. Drove it 45 miles or so, turned it off, turn it back on and the CEL comes on with the same codes P00135 and P0030.

Double checked the flex pipe this morning out of paranoia, it's totally fine and probably in better shape than most of the car. Does all this mean I'm looking at a wiring issue? The wires looked fine to me. I've also checked fuse 33 and it looks just fine to me as well.

Help?

 

Welcome to the site, P0030 shows possible causes of loose or broken wires, double check your connections and the ground wires. Check the fuse box under the hood they are known to get loose and cause problems

https://www.obd-codes.com/p0030


P0135 pertains to the same thing loose or broken wires

https://www.obd-codes.com/p0135


I was just speaking with my GM service advisor, she said nine times outta ten O2 sensor problems are wiring harnesss related. So check for burnt wires, loose grounds and such.

 

Thanks, any suggestions on going about checking those wiring connections? I'm not an electrician and the fuse box wiring seems like a bit of a nightmare. Any specific wires I should be watching out for? Where are the ground wires located?

Thanks again!

 

Ah, we have threads for that!

https://www.chevyhhr.net/forums/how-...cations-56504/

 

Don't just look at fuse #33. Check it with a VOM.

If fuse #33 was bad you should also have a code for the EVAP system, it also supplies the EVAP vent valve (next to the gas tank).

Look for any wire leading to either O2 sensor getting close to a hot or sharp surface.

Sounds like it may be the low ctrl wire that is shorted, could be either to ground (a wire burned on the exhaust) or to + (both wires broken and touching).

The heater is not essential to normal operation of the car, you may get poor mileage until the sensors heat up by themselves and the engine goes into closed loop operation. IF these are the only codes.

The O2 sensors have a "low ctrl" not exactly a ground which is supplied by the ECM. The ECM ground is on the left side of the radiator support.