U0143 — Lost Communication With Body Control Module C

Causes

• Faulty Body Control Module (BCM C)
• Open/short in the vehicle data bus (CAN, LIN or manufacturer-specific bus)
• Missing or low module power or ground
• Blown fuse or fusible link feeding the BCM
• Corroded/loose connector pins at the BCM or gateway module
• Water intrusion or physical damage to wiring or connector

Symptoms

• Multiple convenience features inoperative (door locks, lighting, wipers, etc.)
• Warning messages or lamp illumination on the dash related to body systems
• Remote keyless entry, alarm or immobilizer faults
• Other control modules report inability to communicate with BCM
• Intermittent or permanent loss of features controlled by BCM
• Possible no crank/no start if BCM provides inhibit functions

What to check

• Read all stored U-codes and freeze frame with a capable scan tool; note module presence list
• Check battery voltage (should be >12.2 V) and charging system condition
• Inspect fuses/fusible links that feed the BCM and related modules
• Visually inspect BCM connector and wiring for corrosion, bent pins, or water damage
• Check for recent repairs or aftermarket accessory installations that tap into the data bus or power
• Verify other modules on the same bus are present and communicating

Signal parameters

• CAN High and CAN Low differential voltage at the BCM (idle ~2.5 V each, differential ~0 V; active frames ±1 V differential)
• Presence and frequency of expected BCM message IDs on the bus (scan tool datastream)
• Module supply voltage (VBATT) and ground continuity at the BCM
• Wake/sleep line status if vehicle uses a separate wake signal
• Bus error counters / bus-off status reported by other modules
• LIN or other secondary bus traffic if BCM uses sub-buses

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