My husband has a 2009 HHR LT, 140K mi., that had a check engine light on: AutoZone test said exhaust manifold issue, and lean mixture. After extensive testing at an indy shop, then Chevy service, they found a cracked exhaust manifold, and O2 sensors but computer kept saying lean mixture. It was determined that the wiring harness' connection to the oil pressure switch for the A/C was pushing oil into the O2 connectors and computer module. They are trying to source a replacement harness, but it's been discontinued by Chevy. All the resources so far are out of it, and indicate it's discontinued. Can anyone out there help find one? Thanks!

 

Hi Susie, to the forums!

Either you've misunderstood, or they haven't a clue how to fix cars. The O2 sensors are behind the engine, and the oil pressure switch and AC compressor are in front. There is no logical travel path for oil to get to the O2 sensors from the front.

That being said, if they could provide a GM part number, one could search for it via Google. Otherwise, they'll have to go to a wrecking yard for a used harness.

 

My husband said the Chevy dealer mechanic showed him that on the left end of the harness is where it connected to the A/C pump, onto the pressure valve, and when removed, it had fluid in the connector, as well as
the connectors for the ECU and one O2 sensor also had it. I assume they are checking sources beyond Chevy to locate one, perhaps a used one. Thanks for the help!

 

There is no oil anywhere near the AC compressor and the O2 sensors are 3 feet from there all of the computer modules are near the fuse box, another foot away.. By cracked exhaust manifold I bet the mean cracked flex p[ipe.
I have no idea how oil can travel several feet on a wire. The individual connecter are widely available and part numbers are easily found.

Has the engine been "steam cleaned"? That might be a source of liquid in the connectors.

I agree, either there is an understanding gap or some mechanic is trying for a big pay day. The only reason you might need a engine harness is an under hood fire.

 

Oil pressure sending unit is on the driver’s side front of the engine, above the starter.
AC compressor is on the passenger side front of the engine, down below the coolant hose and fill cap.
the 2 O2 sensors are behind the engine in the catalytic converter down pipe after the exhaust manifold.
I don’t see how the oil can leak out of the oil pressure sending unit onto the other components, it must be a nasty leak from the valve cover.

 

The pressure switch they are talking about is the AC pressure switch. I guess the shop is claiming that condensate and compressor oil is traveling up the wires.
I find it hard to believe that a competent mechanic would ever say something like that. GM mechanics have no better training than "Jose down the street does", don't put any more trust in them.
In any case. the individual connectors are readily available and the wires don't care if they are wet. Only a fire can damage the wiring harness enough to need replacing it.
Water evaporates, oil can be cleaned of with chemical sprays.

 

Hello htrdsusie, I concur with OB&DB veteran successful advice posters here.
You didn't mention what codes were set for the lean mixture troubles or if performance are evident as well.
Lean mixture could be set with outside air mixing in at the "cracked" manifold and be the culprit setting the CEL.
The harness replacement sounds a bit fishy and I would approach that diagnosis with a large dose of skepticism.
Any labor estimate on this procedure? I'd expect a large number. $$$$ Good luck