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#4690974 - 03/10/18 10:19 PM Diagnostic Fun......
clinebarger Offline

Registered: 12/19/13
Posts: 1912
Loc: Fort Worth, Texas
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.

2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/Auto

#4690980 - 03/10/18 10:25 PM Re: Diagnostic Fun...... [Re: clinebarger]
Richie Offline

Registered: 06/10/04
Posts: 285
Loc: Valencia, CA
Good work.

#4690983 - 03/10/18 10:29 PM Re: Diagnostic Fun...... [Re: clinebarger]
Leo99 Offline

Registered: 03/30/14
Posts: 3048
Loc: NJ
What would cause damage to a spark plug like that?
Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles
2004 Rav4 359,000 miles
2015 Camry 59,000 miles

#4690988 - 03/10/18 10:35 PM Re: Diagnostic Fun...... [Re: clinebarger]
BrocLuno Offline

Registered: 09/06/15
Posts: 5519
Loc: Kalifornia Kollective
Who in their right mind runs E3 plugs? Talk about shielded arc and contained corona ...

Nice save, bet you'll get the work in the future.

O'Scope is a great diagnostic tool smile
Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.

#4690994 - 03/10/18 10:42 PM Re: Diagnostic Fun...... [Re: clinebarger]
Warstud Offline

Registered: 09/02/05
Posts: 5397
Loc: MIchigan
Before I read you solved the problem I was thinking you need to ask the owner what aftermarket non-oem parts were installed. It looks like the wrong plug can wreak all havok.

#4690997 - 03/10/18 10:46 PM Re: Diagnostic Fun...... [Re: Leo99]
clinebarger Offline

Registered: 12/19/13
Posts: 1912
Loc: Fort Worth, Texas
Originally Posted By: Leo99
What would cause damage to a spark plug like that?

Manufacturing defect, Dropping the plug, Using the wrong socket/rough tool handling....Take your pick! If I had to guess, I would say it was dropped & it hit something with an edge?
2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/Auto

#4691016 - 03/10/18 11:19 PM Re: Diagnostic Fun...... [Re: clinebarger]
dishdude Online   content

Registered: 11/14/08
Posts: 8754
Loc: Phoenix
Nice detective work! Amazing how the simplest things can cause the craziest issues in modern cars.
2018 Challenger SRT

#4691026 - 03/10/18 11:42 PM Re: Diagnostic Fun...... [Re: clinebarger]
dailydriver Offline

Registered: 03/14/06
Posts: 9176
Loc: Pennsylbammyvania
GREAT detective work! thumbsup cool

I will stick with NGK Laser Iridiums for my car, they can keep their Brisks, E3s, etc. wink

I CAN see someone cracking the ceramic part of a plug upon installation into an LSx's head, being that you are basically working 'blind', and by feel only when doing this job, on a f-body, or y-body application's extremely tight engine bay.
It is also almost impossible to properly torque the plugs in these apps because of the angles involved. frown
2016 Ford Fiesta ST
Ravenol REP 5W-30
Amsoil Ea15K51 filter
Motul Gear 300 non-LS 75W-90

#4691055 - 03/11/18 01:30 AM Re: Diagnostic Fun...... [Re: clinebarger]
Shannow Offline

Registered: 12/12/02
Posts: 39871
Loc: 'Stralia
Really good and professional diagnosis.

It's amazing at times what one single, simple issue can do in creating scenarios that have you looking everywhere.

#4691059 - 03/11/18 03:07 AM Re: Diagnostic Fun...... [Re: clinebarger]
Silk Offline

Registered: 07/26/03
Posts: 4562
Loc: New Zealand
These days the first thing you do is plug in the scanner...previously we hooked up the scope. A good scop would've picked this up first. As always, the fault is the last thing you look at...regardless of how many things you looked at before you found it.
1987 BMW R65 - Penrite V Twin 20/50
2005 Nissan Expert - Gulf Western 10W-40
1996 Volvo T5 - Penrite HPR15 - 15W-60. Ryco syntec filter.

#4691070 - 03/11/18 04:26 AM Re: Diagnostic Fun...... [Re: clinebarger]
Olas Offline

Registered: 12/11/13
Posts: 3933
Loc: Manchester, England
Scanner or scope you should always check the ignition system from top to bottom if you have to look any part of it - never just isolated components in the circuit.
Cable ties should hold it

#4691089 - 03/11/18 05:32 AM Re: Diagnostic Fun...... [Re: clinebarger]
Claud Offline

Registered: 02/11/14
Posts: 593
Loc: Margate England
Back in the day the mechanic would take a look at the plugs first. Before plug in diagnostics I mean. They would tell him (or her, though female mechanics were very rare back then) how the engine was running and if a particular cylinder was the problem.
But nowadays it might take an hour simply to gain access to them.

I jaguar came into a shop I worked in recently, the driver was complaining of poor response and the eml was on. The plug in diagnosis told of all kinds of faults, then I pointed out I could hear hissing like an air leak - so could everyone else - and found a breather hose had split. It took me maybe a minute to find. I make no claims about being a genius mechanic, but often it pays to look for the obvious, computers will only do as they are told, an air leak or bad plug might be beyond a computers imagination.


#4691126 - 03/11/18 07:43 AM Re: Diagnostic Fun...... [Re: clinebarger]
Audios Offline

Registered: 11/19/11
Posts: 888
Loc: Lyndhurst NJ
Good find, its always so [censored] when someone gets mislead by all the marketing hype and it costs them thousands, especially when the expenses is coming from the mouth of an untrained tech. We had a similar issue, customer with an e46 330xi had misfires across the board. He did plugs and coils already. We changed PCV from a cracked hose, and split housing and was still running poorly, better but no balls on acceleration, and no faults at idle only acceleration. Well Pep Boys told him E3 were the latest and greatest plugs, and guess what caused all of the faults and threw the owner for a loop since he thought the plugs had no affect. A set of OE BKR6EQUP from NGK and the car ran perfectly with 170k.
2002 VW Golf TDI-Mobil 1 5/40 TDT
2005 BMW M3 BMW Twin Power 10/60
1998 BMW M3/4/5 Fuchs 5/40
2007 Mercedes GL320 CDI Fuchs 5/40 GT Pro XTL

#4691172 - 03/11/18 08:20 AM Re: Diagnostic Fun...... [Re: clinebarger]
klt1986 Offline

Registered: 04/08/09
Posts: 384
Loc: Southern VA
Great job! Hopefully you gained that customers' trust and he will come to you when work needs to be done to his vehicles.
Wife: 08 Honda CR-V 4WD, M1 5W-20
Me: 11 Toyota Tundra DC 4WD 5.7L, PP 0W-20
Me Work: 06 Ford Explorer 4WD 4.0L, Pennzoil 5W-30
Son: 14 Toyota Corolla S, M1 AFE 0W-20

#4691205 - 03/11/18 08:56 AM Re: Diagnostic Fun...... [Re: clinebarger]
NHGUY Offline

Registered: 10/09/11
Posts: 5043
Loc: USA
But...E3s are the late great SplitFire plugs....they burn cleaner and deliver more hp and MPGs than any conventional plug...really...honestly.....says Green Acres Huckster Mr

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