420 SEL - Maddening Check Eng Light problem
 

I've posted a bit on this before, trouble with a repair shop that did engine work on my car and ever since a rough idle and check engine light. But, now I have more info...

The trouble code keeps coming up as 09 E.H.A. out of range due to engine temp or voltage input.

The shop working on the car replaced the coolant temp sensor, thermostat, CIS Air Temp Sensor, Overload Relay, Alternator......all to no avail, the light keeps coming back.

They tell me it can't be related to their valve repair work, but I'm skeptical since that is when it started. Had the car in to this place 8 TIMES!!

So...I'm hoping someone out there might have some ideas on where else to look. This problem has been nightmare and I'm going to take the car to another shop, but don't want to continue to throw parts at it in hopes it cures the problem.

Could a sticking valve indirectly trigger a check engine light? What other things to check?

Your mixture might be off. If the mechanical mixture setting (same as the CO adjustment) is off, the Lambda controller cannot bring it back to normal and the light comes on. Check the on-off ratio at the diagnostic socket to see if you are out of adjustment.