After hitting a large bump in the road while raining outside: ABS light, Check Eng Light, Tire Pressure Light, Eng Temp gauge fluctuating to max, A/C compressor disengage, Cruise disengage, Tach not working, Speedometer not working.

Swapped out the Tac, speedo cluster, and BCM with 2006 R53 JCW GP: all 2003 work in the 2006, none of the 2006 work in the 2003. Checked: body ground wires, connectors in R & L kick pads, no water intrusion on BCM. Only fuel gauge works.

 

I haven't ever done any testing on the CAN network in a MINI, but we use CAN and J1939 in the systems the company I work for manufactures, so I have some experience with the architecture.

Basically, a CAN bus is a pair of wires that connect to each device on the network. The network is laid out so that there is a main "trunk" that covers the distance between modules, and "stubs" that T off the trunk to each module. At each end of the main trunk there is a 120Ω terminating resistor. Yellow (or white) and green (or blue) are standard colours for CAN; not sure if MINIs adhere to that standard..

In a properly functioning CAN (or J1939) network, you should be able to measure 60Ω between the yellow (CAN H) and green (CAN L) at each stub module connector, and there should be an open circuit to ground on both lines. Best to do that testing with the car battery disconnected; If you measure voltage between CAN H and CAN L with the car turned on (battery connected), you may see some low voltages, 2.5 to 5ish volts, depending on how much traffic there is on the network, but it's pretty meaningless.

By measuring the resistance at each device, we can sometimes narrow down where the harness might be damaged. If the harness is dead shorted (0 Ω between CAN H and CAN L) it's pretty tough to trace. If we can locate the terminating resistors and unplug one at a time and then test resistance at each module, that can sometimes be really helpful.

So, does anyone have a drawing of how the CAN bus is laid out in this car?