Initial measurements
The suspected good and faulty inputs showed different resistance behaviour to ground and sensor ground. Because several readings changed continuously as capacitors charged, a single resistance measurement could not support a reliable diagnosis.
Confirming the connector mapping
The connector labels in the factory diagnostic table had to be reconciled with the controller’s physical C1/C2 connectors. Only after identifying the machine-side CAN wires could each terminal function be interpreted correctly.
- separating sensor ground from main ground;
- measuring input resistance in both polarities;
- identifying machine-side CAN wiring;
- comparing a known-good channel with the suspected channel;
Key lessonA measurement difference on the PCB is meaningful only when the connector identification and external harness wiring are both confirmed. Incorrect pin mapping can easily lead to a false component-level diagnosis.
Next diagnostic step
After resistance testing, the inputs can be stimulated with known signals under current-limited power, followed by load testing of the output stage. This separates an internal controller fault from sensor or wiring faults.