07 6.6L Turbo diesel keeps popping EGR 402 codes. GM cleaning procedure
done ($90). EGR Valve replaced (free). No codes for a couple weeks then
bam… three times in the last week. Reset with code reader each time to
see if it was a stray code or a real problem. So what to do next? The
dealership should be responsible at this point for tracking down the
problem, but apparently they don’t know how.
Is there some kind of solenoid that controls the EGR valve? That’s where I would suspect next. Could be just a flaky connector.
how about the flow sensor itself?