A buddy of mine bought a stock 99 z28 with a p0336 code.

He had the CPK and cam position sensor replaced with no luck, so he dropped the car at my place to try and figure out the issue. I've noticed that when you clear the code and start it cold it runs fine and as it warms up it starts to missfire on about 4 cylinder and idles and backfires badly whem you rev it a little, at the same time the tach on the cluster drops to 0 but the OBD port shows RPM signal on the scanner.

Looked around the harness for any issues with no visible indication

Tested voltage at ckp ignition pin and it reads about 11.4-11.7 volts while the battery is at 12.8 ish

Tested the cam sensor voltage and it reads about the same as the ckp

The ground seems fine for both sensors

Could not do a crankshaft variation relearn due to the code being triggered

Pulled the new ckp sensor out and noticed a few vertical scratch lines (reluctor wheel touching?)

Been chasing the harness for the past couple of weeks for any issues and all seemed fine

I've pulled the tune file on the car and noticed it had a 2001 Pontiac firebird PCM with the VIN unchanged (the car is a 99 camaro), and the VAT disabled

The tune seemed like it has been played with

Driver side o2 is missing and the STFT/LTFT were disabled within the tune file of that PCM

Now i do understand the a scope is needed to read the ckp square wave signal etc sadly don't have access for one. Also i understand the crankshaft end play and it's relation to the ckp signal (still waiting on a dail indicator gauge).

What's the min/max voltage for the ignition ckp/cam sensor?

And how do i tell if the pcm is bad?

Is a 2001 PCM compatible for a 99?

Can the vin effect anything if unchanged when they swapped it?

Is there a certain amount of clearance required between the ckp and the reluctor wheel?

Any feedback would be appreciated in this endless p0336 situation thanks

 

Update on the issue.

It was two bad brand new AC Delco CKP. The third used one fixed the issue....