I would like to known if there is a publication of known good PIDs. As I read my data, I would like to know what a good average is to make a diagnosis. Example MAF frequency, what is an ok average frequency or MAF gm/sec, what is a good known PID. Is there some kind of chart available?
Hello Peter I'm not aware of such a chart as it's different for every vehicle but as a rule of thumb your maf grams per second should be approximately your engine liters at warm idle so for example a 1.8 liter engine should idle at about 1.7 to 2.0 grams per second and a 5.4 should idle around a 5.2 to 5.6 grams per second, now manufactures give specs at 2500 rpms for checking higher flow rate but I like to use max reading on wide open throttle as it can show a dirty maf better than at 2500 rpms so for example if you have a voltage pid you want it to be able to go over 4.0 volts at wide open throttle full load(1st and 2nd gear) if voltage is not available I guesstimate on prior experience what the engine should be able to draw in the case of a 5.4 engine it should pull over 200 grams a second where a 1.8 will be closer to 70 grams I use a formula of liters x 40 for peak flow so 3.0 liter engine idles close to 3 grams and peaks at 120 grams. Sorry it's long winded but I wanted to make sure everyone could understand it , there are a few exceptions on this formula such as diesel vehicles aren't even close to this!
Sometimes manufacturers will make "normal" pid values available in service info, but it's not always available or easy to find.
iATN.net is a good resource where you can find known good waveforms posted by techs and ask questions about PID values. And of course you can always open a thread in the repair questions sections of this forum if you're seeing something you're not sure of.
