B14C3

Code

Generic B — Body

Body Control Module CAN Bus C Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 12 RU: 9

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Page language: EN

Causes

Damaged or shorted CAN wiring (CAN_H/CAN_L) on Bus C
Loose, corroded, or water-intruded connector at the BCM or other node
Missing or failed termination resistor(s) on the CAN bus
BCM lost power or poor ground connection
Faulty BCM or another module on Bus C pulling the bus low/high
Incorrect software/calibration or failed reflash after module replacement

Symptoms

Loss of BCM-related functions (lighting, door locks, wipers, etc.)
Intermittent or permanent communication errors with other modules
Associated U-codes (module not responding) on full system scan
Multiple body systems behaving erratically or not responding
Dashboard warning lamp(s) for network/communication faults

What to check

Scan vehicle with a capable scan tool; record B14C3 plus any related U- or B-codes and freeze frame data
Check vehicle battery voltage and BCM supply/ignition power circuits (key on and engine off conditions)
Visually inspect BCM connectors and CAN harness for corrosion, bent pins, water intrusion, chafing or obvious damage
Measure CAN termination resistance (CAN_H to CAN_L) with ignition off — expect ~60 ohms (two 120 ohm terminators in parallel)
Probe CAN_H and CAN_L single-ended voltages and differential with key on using a DMM or oscilloscope
Check for aftermarket modules/devices tapped into Bus C and disconnect them for test

Signal parameters

CAN bus idle (recessive) single-ended: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (typical tolerance ±0.5 V)
CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
Termination resistance (CAN_H to CAN_L) with ignition off: ≈ 60 ohms (±5-10%)
Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate)
Voltage reference: measurements with high-impedance meter or oscilloscope; low-impedance loading can alter readings

Diagnostic algorithm

Retrieve all stored DTCs and freeze frame with a scanner. Note any related U-codes or multiple BCM/Bus C faults.
Confirm battery state (fully charged) and verify BCM supply power and ground presence at the connector (reference wiring diagram). Repair any low-voltage or ground issues.
Visually inspect BCM connector(s) and CAN wiring for damage, corrosion, or water ingress. Repair or replace damaged connectors/harness sections.
With ignition off, measure resistance between CAN_H and CAN_L at an accessible point. Expect ~60 ohms. If open or shorted, trace and repair wiring or missing terminator.
With key on, measure single-ended voltages at CAN_H and CAN_L. Compare to expected values. If voltages are pulled high/low, isolate the offending node by disconnecting modules on Bus C one at a time (follow OEM safe isolation procedure).
Use an oscilloscope (preferred) to view CAN frames and noise on the bus. Look for missing frames, bus errors, excessive jitter, or a node constantly dominant.
If a specific module is identified as causing the fault, repair or replace that module. If BCM is suspected after isolating the rest of the bus and verifying power/ground/terminations, consider reprogramming or replacing the BCM per manufacturer procedure.
Clear codes and perform a road test or functional test to confirm the fault does not return. Re-scan for any reoccurring codes.
If aftermarket devices are present, remove them and retest. Ensure any replaced module is programmed/configured correctly for the vehicle.