Silly title I know, but these are the codes I've extracted from my "new" HO 2500 with 173000 miles.

I'm pretty sure I get what the PDONE code is, but what is PECM and -------?

Thanks!

 

no codes...just saying that it is checking the Engine Computer for codes (ECM)

 

Reading the codes with the on, off, on, off, on key trick, it should go thru 2 cycles. 1st is the PCM and the 2nd is the ECM. After the 1st Pdone, it takes a few seconds for the next code reader to start. No numbers coming up is a good thing.
Another key trick. Hold the odometer reset in and turn the key to on. It will say check in the odometer window, then the odometer will do a snake dance, and check all the leds. The warning light in in the instriment panel will come on and the gauges will go up, 1/4 1/2 and peg them. Cool to watch.