P0449 06 silverado 1500 lt

Hello, I have an 06 silverado 1500 Lt. I'm getting code p0449 with a new vent valve. I'm getting a dim light on test light when connected from battery positive to control wire. When commanded the lights goes bright....but still ON and dim when not commanded.
Can someone please help?
Thanks

P0449: The commanded state of the driver and the actual state of the control circuit do not match

So basically, with the vent circuit electrically off (no current flow), the PCM expects the control wire to be at battery voltage too.

Your test light continuing to stay dim means there's a resistive short to ground on the control wire, somewhere. It's not a complete short to ground, but probably a green crustified path to ground.

It's a lot of wire to eyeball and unwrap from the loom so best to cut this problem in half and figure out if the problem upstream or downstream of the so called "cut." Hopefully you can find a connector that's easy to find and break this circuit down. Or leave your light in place and start moving any suspicious wires down there and if the light goes out, you've found the problem area.

also, does the test light stay dim even with the key off? I'm thinking the wire could be shorted to another ground switched circuit and if that other circuit shuts off with the PCM, the dim test light may go out with the key off.

also, the vent valve is supplied B+ at all times so if it's a persistent short to ground, this is a parasitic draw you need to fix before it potentially leaves you stranded.

Thank you so much for the help.
Everything checks out good for wiring ,
It looks like as soon as I disconnect the pcm the light goes out....so my driver is shorted right? I guess I'm in for a new pcm

And to follow up the text light does not stay on with key in off position.

Rshog5016 wrote:

It looks like as soon as I disconnect the pcm the light goes out....so my driver is shorted right? I guess I'm in for a new pcm

When you disconnect the PCM you're not just disconnecting the single vent circuit but a whole bunch of other wires from the PCM and I'm not certain yet the PCM is the culprit just yet.

I would second your call on a new PCM if you could cut the vent control wire, in a repairable spot, a few inches from the pcm, just to isolate that circuit, and redo the test light test again at the freshly cut wire. Test light to battery positive and shoved into that cut wire from the PCM. If it still lights up with the key on, then yes the driver's bad Try banging on the PCM at that point haha.