2002 Gmc Sierra Flashing Check Engine Light

[cganey77]

Hi I have a 2002 gmc sierra 2500hd the truck has about 70k miles on it. When on the highway around 75mph my check engine light will flash repeativly and go away and flash and go away. I brought the truck to autozone and the scan came up random misfire. Does anyone know what this proublem could be. I have already changed the spark plugs.

Thank You,

Chris

[Coolmaker]

What plugs did you put back in? Bad plug wires, vacuum leak, low fuel pump pressure, bad injector, partially clogged fuel filter, and a maze of other things will cause that code. I recently had it happen to my work van and changed the fuel filter and all is well now.

[Shaners]

My guess would be crank position sensor.

[hockeypro1411]

Do a search on here for it. I replaced every wire, sensor, and gasket on the damn truck until I found out it was actually a bad ignition coil. One cylinder misfires and that causes the one behind it to hesitate and miss also, hence the random/multiple misfire code. Try pulling plug wires off either the plugs or the coils while the truck is running. If there's no spark arcing across one of them then that's your problem.

 

Edit: Wear a glove to avoid shocking the shit out of yourself.