A weird new one: SPN 1231 FMI 9

It says "Emission System No Comms Detected. 25% derate"

And the truck goes into auto shutdown.

It's been sitting for a couple of days and got jumpstarted and then this began.

Is it a loose wire or perhaps a blown fuse somewhere or something?

 

I checked the fuse in the power distribution box, I unplugged and replugged the ACM... now on my way to Walmart in an Uber so I can buy a proper voltage tester (it's 10pm here and it's the only thing that's open)

 

Possible causes: • Over/under voltage supply to the ACM module • Fault set during a reprogram event • Loss of power to the ACM • Loss of ground to the ACM • Loss of ignition switch power to the ACM • Open in the CAN-H/Can-L communication circuit to the ACM

 

Yes, I have that PDF too lol

 

Had something very similar in a DD13. Shortly after delivery this truck dropped the driveline because the front u-joint wasn't tightened up. It did a good job of wrapping and pulling some of the wire harness. 2 years later the communication line to the ACM finally grounded out where it had been pulled tight against the OneBox. IIRC, he was in the shop for a week before they finally found it after running out of parts to throw at it.

 

That's exactly why i'm going under there with the multimeter. It is ~probably~ the harness and a grounded wire, but I want to be sure. Even if I don't end up changing the harness myself, I don't want them throwing a new ACM at me for no reason.

 

Update: I found the bad wire!

Spliced it with some random wire i scavenged from a 12v charger, and i'm good to go. Saved myself at least a couple grand and a two day delay...