I am new here and I hope i am in an appropriate Forum for my inquery. From what ive read it seems reasonable.


B.L.U.F


P1345


I want to reset the CaMshaft Position Retard Angle PID in the EVAP EGR Data. Really I want to make the SMOG god happy and save some gas money and not have to limp up grades. I'd also like to stop buying distributors for this '99 K1500 5.7L Suburban but that won't happen.

I am an Electrical Engineer and I have a PLC in my garage i use for random things . I figure i could program the PLC to send a string of data through my Dash OBDII port that opens the bus and sends data using the SAE J1850 VPW protocol to reset CMP Retard to Zero or whatever value is needed.


So my question is if anyone could tell me the correct sequence of hex to send to simply write one value to that register? Also any other thoughts on the situation. It seems there is no consensus among among internet people about 5.7L Vortec distributors, I assume because the older ones had turn the thing timing and the newer ones didn't even though some new ones came with a round hold down bracket that allowed a few degrees and aftermarket dist. Had a rectangular that allows nothing. I am thoroughly fed up trying to find the truth of the matter but a little pain to spike the pleasure is good so if you guys have any really good explanation/advice/rants I would appreciate the input.


i have the protocall timing as follows:




SAE J1850 VPW
Feature Description
BUS + Pin 2
12V Pin 16
GND Pins 4, 5
Bus State: Bus idles low
Maximum Signal Voltage: +7V
Decision Signal Voltage: +3.5V
Minimum Signal Voltage: 0V
Number of bytes: 12
Bit Timing: '1' bit -HIGH 64uS, '0' bit -HIGH 128uS, Start of Frame - HIGH 200uS


Thank you