03 CDL wiring
You need continuous ground. Those switches are known to be flaky, (at least at my house....) possibly due to lack of use, but to add insult to injury they're like $50 a pop. I put in a manual switch in mine using some spare dash switches because I don't trust them and they're too much of a PITA to swap out. Same principle, feeding ground to the SLABS ECU, but using a manual switch instead of the pin switches in the TC. Not for everyone but it works for me.


Last edited by ahab; Apr 11, 2021 at 06:24 PM.
A continuous ground would cause the light to be on all the time. All the CDL switch does is connect the signal wire to ground. You can do that manually, or you can do it with the switch on the t-case.
Sorry, poor grammar on my part. You need a continuous ground whenever the TC is locked, as opposed to a brief indication of a connection. In order for HDC to function the ground signal needs to be present on Pin 7 of C0668. When the TC is unlocked then the ground signal to SLABS should go away.
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