U0073 — A faulty control module, A problem with the CAN bus

Causes

• Failed or intermittent control module (ECU/BCM/gateway)
• Open/short in CAN_H or CAN_L wiring
• Poor power supply or ground to one or more modules
• Missing or incorrect termination resistor(s) on the CAN bus
• Connector corrosion, water ingress or damaged pins
• Software mismatch or corrupted module software/configuration

Symptoms

• Malfunction indicator lamps or communication-related warning messages
• One or more modules report ‘no communication’ or unavailable data
• Features controlled over CAN do not operate (e.g., instrument cluster, ABS, infotainment)
• Intermittent system operation or random fault appearance/disappearance
• Possible loss of drivetrain control or no-start if powertrain module is affected

What to check

• Read and record all U‑codes and freeze frame data from every module with a professional scan tool
• Check battery voltage and charging system; ensure stable 12 V supply during tests
• Visually inspect CAN wiring harnesses, connectors, and module grounds for damage, corrosion, or water intrusion
• Check for other modules reporting loss of communication or related codes to locate bus segment
• Measure termination resistance between CAN_H and CAN_L with ignition off (expect ≈60 Ω total)
• Use a scan tool or CAN log to confirm presence/absence of bus traffic and message IDs

Signal parameters

• CAN recessive voltage (idle): ~2.5 V on CAN_H and CAN_L (both equal)
• CAN dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V (differential ≈2.0 V)
• Expected termination: two 120 Ω resistors in parallel ≈60 Ω across CAN_H and CAN_L
• Common bus bit rates: 125 kbps, 250 kbps, 500 kbps (verify vehicle-specific rate with OEM tool)
• Voltage tolerance: signals referenced to battery/ignition voltage; tests should be done with stable 12 V supply

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