Hacker News new | past | comments | ask | show | jobs | submit login

Yes, that is one of the strong points of CANBUS. Like I said in the original post, this was a very rare failure. However, the APIM managed to spam the bus in just the right way where it de-synced modules; when I initially connected to the vehicle w/ a snap-on scan tool it was throwing codes for BCM and TCM non-comm, as well as codes that implied the ECM was seeing different speeds on the CKP & CMP (crankshaft & camshaft sensors). The CKP/CMP disagreement was what caused the vehicle to be 'bricked', since the engine management had no idea where the crankshaft & valves were in relation to each other.

Near as I could tell from my scope, the APIM was spamming the bus with exactly the right frequency to interrupt the ECM during it's scan of critical sensors. It was an extremely rare failure, and to Ford's credit they covered both the repair as well as my shop's diagnostic time.

edit: To make it clear, I have seen 2 vehicles that still operated with a direct CANBUS short to ground, as well as a vehicle that had CANBUS shorted to 12V+. In these cases, aside from expected failures (such as the BCM systems not responding, or transmission limp-home), modules were able to fall back into either safe states (limp-home, in the case of the TCM) or just a dashboard warning light (in the case of BCM no-comms).




Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact

Search: