C1340 - Open Circuit in CDL signal

[JLee]

Anyone have this?

I have the three VSC lights on and this is the only code I have. My 4x4 light sometimes goes into rapid-blink -- the button doesn't do anything if it's blinking rapidly. If it's not blinking, I can push the CDL button and it'll slow blink like it's trying to engage, but it never does.

I found a couple service manual pages and I'm really tempted to just go to a dealer, as much as I hate to think about that...

 

[JLee]

Turns out the 4WD ECU was not fully plugged in.

I had the dashboard replaced under warranty a few months before this happened - I'm thinking the tech may not have fully seated the connector. I plugged it back in and everything works fine.

 

[phishtaco]

That is great news!

 

[Jstawgn]

That awesome. Good to hear the solution is that simple. I suspect wrong connection all along.

Don't feel bad. I spend more than $1k chasing drive train rattle on my other car a few years ago. Bought a used diff and new driveshaft when the rattle finally turns out to be a weak/became overly soft transmission mount that only cost $50 to replace.

 

[JLee]

Come to think of it, when I bought the truck 2 years ago the blower motor was bad. The seller replaced it prior to me taking possession...I bet it wasn't fully seated and worked loose after a year.

 

[JLee]

The more I think about this, the more I think it was a multi-faceted problem. When I replaced the master cylinder / skid control ECU, C1203 went away but C1340 did not. C1203 is potentially a skid ECU fault. I was talking with a friend this morning and remembered a time I had to use my CDL to get out of some mud because traction control wasn't working, so there was a time where my CDL wasn't working and also I had an angry TSC/TRAC system.

Seems plausible to me that the skid ECU was bad (causing C1203) in addition to the 4wd computer's plug being loose (causing C1340 and non-functional CDL). Replacing the skid ECU eliminate C1203, then as soon as I plugged the 4wd computer in all lights cleared and we were functional again.