Victim: 2007 Corvette 6.0L-LS2 32,xxx miles.
*Symptoms: Random Service Charging system message, Random Service ABS/TCS message, Radio shut down at high RPM, Random HVAC shutdown, Random harsh shift.
*DTC's: P0622 "Generator Field Duty Cycle circuit fault" P0300 "Random/Multiple misfires detected", ALL Class 2 modules have High & Low voltage codes.
*Work performed before it got brought to me: Battery replaced, Several Alternators, Generator control circuit wires replaced, ECM replaced, Ignition Switch replaced, Several ground straps added.
First thing I did was clear the codes & test drive the vehicle, P0622 sets within a 1/2 mile, Voltage PID fluctuates wildly between 10.1 VDC to 15.3 VDC, Generator Field Duty Cycle seems steady per the PID.
Go through the P0622 trouble tree, Inspect all the connector pins, Load test the generator control wires with a halogen headlight bulb, Removed the Alternator & had it tested.
At this point I'm kinda stumped! Break out the old Vantage Pro Oscilloscope to scope the Field circuit.......That's when I knew something was wrong! The waveform looked like a wacky secondary ignition-square wave hybrid that got worse with RPM.
Then I thought on it for a little while.....All I could come up with is Secondary Ignition interference on the Field circuit.....Checked out the spark plug wires, They are factory & look to be in good shape. Took a spray bottle & misted the plug wires with water.
Number 3 plug/wire was arcing against the exhaust manifold, Pulled the plug wire & swapped it with #5, Still arcing!
Pulled #3 plug & this is what I found..........POS E3 with a nice crack in the porcelain.
8 new AC-Delco Iridium plugs is all the car needed. The P0300 was the clue that I ignored because the P0622 was a "fix-first" in my mind.
With the customer at his wits end with this car & the fact he spent a few grand already on part changing/misdiagnostics ......I only charged for the tune-up with hopes to gain future service work.