Turn Engine off, CEL turns on?

[badge49]

Has anyone had this problem? I'm stumped.

I turn off the engine, the Check Engine Light turns on. No big deal, except it 100% kills my new Yellow Top in less than 12 hours. The light stays on with the key out of the ignition and in the "accessory" position. When I turn the ignition to "on" or start the engine, the light goes away. My OBDII scanner doesn't see the CEL code because it goes away when the ignition is on. I have to physically disconnect the batt. every time I park the rig for more than a few hours. The CEL has to be telling me something bigger is staying on (not just the little CEL light).

Maybe a bad ignition switch? Some days it's not a problem and there is no CEL/drain.

 

[budwich]

good guess would be an ignition switch problem.

 

[badge49]

Any way to swap parts from a junker without having to change out the keys? It may be cheaper to just use one of these:

http://www.galls.com/style.html?assort=general_catalog&style=VP007

 

[SuRrEaLNJ]

the cel should stay on in key on - engine off.
are any other lights staying on?
make sure the trucks actually turning off with the key out

 

[badge49]

Ya, that's the problem... the CEL goes away when the key is turned to on. There's no way for me to scan it. No other CELs or lights.

 

[budwich]

on my way back from tennis, a "light" came on. your problem perhaps is not your ignition but your PCM relay is stuck on.... maybe.... check it with a meter.... that's my dollar bet.

 

[79broncojosh]

X2 the PCM relay

 

[badge49]

What's the PCM? Which relay is it? I have extra relays laying around.

 

[2000StreetRod]

PCM relay

The powertrain control module (PCM) is the onboard computer for the fuel injection system and the automatic transmission. The PCM relay is located in the Battery Junction Box. You can try swapping it with the Blower Motor Relay also located in the Battery Junction Box.

 

[badge49]

Just to follow-up...
My problem wasn't the PCM relay, I think it must have been a worn ignition switch. I ended up installing one of those Priority Start units (pictured above) and it works great! I definitely recommend the product to anyone with any voltage draining problems. Thanks for the help!

 

[budwich]

glad to hear you got "somewhere"... how ever... did you actual check the pcm relay both in terms of its "integrity" (ie. resistance of windings, contact operation, etc) along with the "inputs" to that relay with a meter... or did you just try dropping in another relay????

 

[badge49]

I swapped the relay out with several that I new to be working. There was no power running to the PCM slot when I pulled the relay. It did have power when I turned it on. I did not bother to measure resistance. It could be something else hidden elsewhere in the wiring, but I have no other problems. The truck runs fine and although I didn't fix the problem, it works all the same for me. As a bonus, I will never again have a dead battery for any drainage reason.