Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/636156
58 | February 2016 coil's primary side the 5.5 amps of current required to properly fre the coil after the rpms got above about 2,500. The result was the PCM activated FMEM and shut off the injector. I checked all the powers and grounds one more time before installing a new PCM. The next road test provided a great feeling as the truck smoothly accelerated with lots of power, no misfres and no CEL. It was fxed. Not all repairs are easy or straight for- ward. We are at a point in our industry of great change, in the way that things are repaired and diagnosed. There are occa- sional silver bullets on the Internet, and there are repair information databases devoted to collecting common repairs and fxes. But these things are just tools; you have to understand how to use them and when. You need to have a vast understanding of how systems work, or how they were designed to work, but even then you need to have never-ending persistence to over- come all the road blocks that can prevent you from unravelling the most diffcult repairs. ● The Tech Bench The culprit in this case turned out to be a bad coil driver in the PCM. Don't forget that you will need both ignition keys to reprogram the new or good used PCM. Here is an example of an ignition coil ramp on a properly operating coil with a good PCM, able to deliver the required 5.5 amps.