U0125 — Lost Communication With Multi-axis Acceleration Sensor Module

Causes

• Faulty Multi‑axis Acceleration Sensor Module (internal failure)
• Loss of module power or ground
• Damaged or corroded connector at the sensor module
• Broken, shorted or high-resistance CAN bus wiring between module and gateway/ECU
• Open or blown fuse/relay powering the sensor or gateway
• Faulty gateway/BCM/ECU that routes CAN traffic

Symptoms

• ABS, ESC, VSM or traction control warning lamp
• Stability control functions disabled or unavailable
• Possible airbag/warning indicator (if sensor used by restraint system)
• Fault stored in multiple control modules referencing the acceleration sensor
• Vehicle may enter a degraded handling mode or limit performance

What to check

• Retrieve all stored and pending codes from all modules; note freeze frame data
• Use scan tool to verify whether the sensor module is present/responding on the network
• Check battery voltage and charging system (low voltage can cause comms errors)
• Inspect and wiggle sensor module connector and harness for corrosion, bent pins, or damage
• Check fuses/relays for the sensor power circuit and related gateway/BCM fuses
• Visually inspect CAN bus wiring and grounding points for chafing or repairs

Signal parameters

• CAN bus idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 2.5–1.5 V (difference ≈ 0 V idle, ≈ 2 V when dominant)
• When communicating, CAN_H should rise toward ~3.5 V and CAN_L fall toward ~1.5 V on dominant bits
• Module supply voltage: vehicle battery ~12 V at module power pin (verify exact pin via wiring diagram)
• Module ground: continuity to chassis ground; low resistance expected
• Check for correct reference voltages (if sensor uses internal 5 V/3.3 V reference per OEM spec)

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