D904

D904 reads "CAS: K-CAN line fault". In one thread a technician was working on an E90 whose engine, engine computer and CAS had been swapped from an N47 to an N57, with the VINs in the computer and the CAS differing from the rest of the car. The CAS, JBE, FRM and IHKA all reported K-CAN line faults. He measured no short of either line to ground or to 12 volts, and replacing the JBE with another changed nothing. The only reply said diesels get little support on that forum.

On a 2011 328i coupe, the owner dates a persistent D904 on the CAS, an intermittent then lasting D104 K-CAN line fault on the RDC, and a head-unit "no communication" entry in ISTA+ to a dealer visit where the FRM was replaced and recoded; everything works. A helper suspected a short in the K-CAN wiring and proposed testing the CAS-to-FRM K-CAN wires after disconnecting their connectors, for a short to chassis ground and between the two lines, and looking for pinched wiring. Another reply was to unplug the RDC and see. The thread ends with a question whether it was ever sorted.