Hi there Glenn Thanks for more input on this

I would think since misfires is part of I/M SMOG testing, and as diag tools say they are complaint they should assure those misfire DTCs are support IF the vehicle's PCM has them

[1998 Chevrolet C1500 Cheyenne, Emissions Photo]

As I do custom PCM/TCM tuning and most cases remotely via emails the owners of vehicles must supply me DTC and scanner recording via testrun they email me to analyze

It is very rare with the tools they are using when there is P0300 multi misfires that also shows the cylinder's misfire DTCs This says to me most of these made in China code readers, scanners claiming they support all vehicles worldwide are only generic and not as in this case, GM enhanced

But to me those P0301-08 DTC are SAE generic so no reason for these tools not supporting those DTCs as without them and just the P0300 makes it tough to debug the problem

Misfire, being triggered by what the crank position sensor reports, can mean anything that causes a stutter on the crank via drivetrain to even a warped brake rotor and only supporting P0300 DTC is useless to debug the cause

Also, GM does not make misfire margins easy Here looking at just one misfire table of a 2015 Corvette you see this is judged by uSecs so no margin of error in tripping false misfires

[2015 Chevrolet Corvette Stingray, Emissions Photo]

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John Rovner
Owner
Team ZR-1 Corvette Racers llc
Greenville, Texas, USA

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