1. Customer Fault Description:
The customer reported that the adaptive module is malfunctioning, the windshield wipers are not working, the transmission system is failing, the display is black, and the engine cannot be started.
2. Technician Fault Description:
Inspection revealed that the vehicle cannot start, the display is black, the instrument panel shows that the wipers are malfunctioning, the transmission system is failing, and the adaptive headlights are not working.
3. Repair Process Description:
Using ISID (2.30.9) to diagnose the vehicle, communication faults were found on K-CAN2 with CSA, FRM, FZD, JBE, and PDC. Analyzing the fault codes, we suspected a fault in the K-CAN2 wiring. The measured High and Low voltage of K-CAN2 was around 4.8V, confirming the K-CAN2 voltage was incorrect. The resistance between High and Low of K-CAN2 was measured at 60Ω (normal). After disconnecting the connector on the FRM, the K-CAN2 voltage returned to normal. We measured each wire from the FRM to check for short circuits and found a short circuit between pin 29 of the FRM A58*3B connector and K-CAN2 (the wire on pin 29 is the power supply line from FRM to the rear ceiling light switch). After disassembling the dashboard, carpet, ceiling, and interior panels, it was found that the K-CAN2 wire was compressed together with the power supply wire for the rear ceiling light at the A-pillar, causing the K-CAN2 short circuit. After repairing the wiring, the fault was eliminated during the test drive.
Summary: When measuring terminal resistance, it is crucial not to measure while powered. In this case, if measured under power, the result will show infinite resistance; after disconnecting the FRM module, the terminal resistance will return to normal. This can easily lead to a misjudgment.
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