ok my truck stoped running a few weeks ago, i was told it was the ECM. just finaly got one today for $1200. pluged it in still no go. in park and neutral no guages work and truck turns over but no start. when i unplug the switch the guages come back but when i ground the middle wire it all goes away again. any ideas? im trying everything i can think of.

 

What a bummer on falling for ECM to fix. diagnois is a must. Apparentlly something is shorted to this wire. It could be the ignition switch or any wiring in the dash area. A short is a unwanted wire to ground or a grounding wire.

 

Have you checked for codes? Possibly the CPS is bad?