Hello. This is my first post here and I could not find ANY information on this fault code at all. The truck is a 2014 Freightliner Cascadia day cab, with a Detroit DD13. It is throwing multiple codes for the aftertreatment system such as NOx sensor codes and a regeneration cannot complete code. The main one I am trying to fix at the moment is coming from the ACM21T module (aftertreatment module), SPN 1669 FMI 9. The only thing I know about the code is that it means "CAN4 No Signal". Detroit is being switched over to new computers at the shop so I cannot access PSL until tomorrow night. I measured continuity on the aftertreatment wiring harness and everything is okay there. No fuses are blown. I couldn't seem to find any terminating resistors on the aftertreatment side, but I reading the resistance through the diagnostic connector is reading okay. Any ideas? any help is appreciated. Thanks.
I am not seeing spn1669 in the GHG14 troubleshooting manual. I found it in the GHG17 manual though. I am attaching the fault diagnostic steps.
