Hey all,

Hopped into the truck this morning, turned they key to start and lost all electrical power (truck did not start, turn over, anything. No electricity getting anywhere)

Thoughts as to what this could be? My auto parts guy suggested either the ignition switch or PDC. I will be testing the switch tomorrow when I get my hands on the proper tool to remove it. No fuses are blown,so it must be something more central.

It's a 2000 quad cab, 4.7 auto. Prior to turning key, electronics were working (interior lights on, remote door unlock).

 

Take the column shroud off, unplug the ignition switch and have a stare at it. See if anything looks melted or "disfigured"

 

No power at all, even the headlights? They don't run through the ignition switch on a 2000.

Check the battery cables are clean and tight. PULL on the ends, they can corrode under the insulation. How's the battery voltage?

 

No the headlights did not turn on either.
Battery cables checked out OK, I will have to check the grounds when the weather clears up.

 

Turns out it was a REAL dead battery. Never seen one go out completely like that before.

 

Crazy I had a very similar issue not too long ago. I would turn the key and all power would go out. No cranking no nothing. Then after some time the power would come back. Battery voltage was good the entire time...so no bad battery for me. Turns out the PCM senses the amps being pulled and can shut everything down. Verified this by looking into wiring diagrams. My starter was going out and drawing too many amps. Hope your battery thing fixes it for good. If not try changing out your starter. Just my .02 if anyone experiences this same problem.

 

What it's actually doing is checking the voltage drop/battery ESR under load. For a computer to measure amps on the order of what a starter pulls, not really possible.

The camaro drops from 18.5 volts to 13.4 volts cranking. Figure the starter pulls 150 amps, 5.1/150 = 0.034 ESR.

Suppose a truck battery went from 13.2 volts to 10.8 volts cranking, on a 75 amp draw. 2.4/75 = 0.032 ESR

Suppose a dead truck battery went from 12.8 volts to 7.3 volts cranking, on a 75 amp draw. 5.5/75 = 0.073 ESR

The PCM doesn't really know the amp draw or the battery's ESR. But it can be dealt with in the programming, if the PCM sees more than an X volt drop at crank, shut everything down to prevent low-voltage damage and throw a battery/SES light.