DIY: Replace dreaded steering-lock on 2009s and early 2010s.

Originally Posted by wstar

It's listed as both an input and an output for the BCM. It seems definitely sure that the BCM is who sends that little pulse train against a 12V background to send LOCK and UNLOCK commands, as an output. I misunderstood earlier that the pulse train came from the lock module.

What really makes no sense is how any of this could be an input back to the BCM. Maybe it's mislabeled (from my point of view), and the BCM drives it at +12V while LOCKED, and 0V when unlocked for 15+ seconds, and whenever it wants to send a command, it applies the +12V (if unlocked before) and then sends the pulse signal.

I guess someone would have to figure out what the manual means by clipping onto this with a scope (or really, even a multi-meter would do, since the only complex bit is already documented in the diagram above).