P0600 — - Communication failure

Causes

• Open, shorted or high-resistance wiring on the vehicle data bus (CAN/LIN/K-Line).
• Poor or corroded connectors or grounds at modules or junctions.
• Failed or intermittent control module (ECU/TCU/BCM/ABS etc.).
• Missing or incorrect termination resistors on the CAN bus.
• Low or unstable battery/charging system voltage affecting module operation.
• Aftermarket accessories or improper repairs interfering with the bus.

Symptoms

• Malfunction Indicator Lamp (MIL) illuminated or communication-related warning.
• Scan tool cannot communicate with one or more modules or reports 'no response'.
• Multiple unrelated systems showing faults or loss of function (ABS, traction, instrument cluster, body control, etc.).
• Intermittent or permanent drivability or network-related warnings.
• Stored communication U-codes alongside P0600.

What to check

• Verify battery voltage and charging system stable (12.4–14.7 V with engine running).
• Connect a diagnostic scanner; note which modules respond and which do not.
• Visually inspect CAN/LIN wiring harnesses, connectors, junction blocks and grounds for damage, corrosion, or looseness.
• Measure resistance across CAN_H to CAN_L at two ends of the network; expect about 60 ohms (two 120 Ω terminators in parallel).
• Scan for additional module-specific or U-codes that identify the non-communicating module.
• Check for aftermarket devices or recent repairs on the bus wiring.

Signal parameters

• CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive state).
• CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2 V).
• Resistance between CAN_H and CAN_L (ends of network) ≈ 60 Ω (two 120 Ω terminators in parallel).
• LIN bus idle: pulled to battery voltage via pull-up; active pulses to ground (varies by manufacturer).
• Oscilloscope waveform: clean differential square wave without excessive noise, reflections or flatlines.

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