U1000 — Electric parking brake ECU not communicating fault: Not characterised

Causes

• Loss of power or ground to the EPB ECU (blown fuse, disconnected/poor ground).
• Open or shorted CAN/bus wiring (damage, chafing, corrosion, pinched harness).
• Poor or corroded connector pins at the EPB ECU or gateway/module connectors.
• Network termination fault or missing termination resistor.
• Gateway/module or other ECU on the same bus is in a bus-off or error state.
• Software mismatch or corrupted ECU firmware preventing normal communication.

Symptoms

• Electric parking brake inoperative or cannot be released/applied via controls.
• Parking brake warning lamp or message on dash.
• Other body/control modules show communication faults or related warnings.
• Unable to access EPB ECU with diagnostic tool (no response).
• Intermittent operation of EPB (works sometimes, then disappears).
• Related features that rely on EPB status (hill assist, auto-hold) not available.

What to check

• Read all stored and pending DTCs across modules; note network and power-related codes.
• Check battery voltage at rest and with ignition on (should be ~12.2–13.8 V).
• Inspect fuses and relays supplying the EPB ECU (replace or test as required).
• Visually inspect EPB ECU connector for corrosion, bent pins, water ingress or damage.
• Verify good ground(s) for the EPB ECU and clean/tighten if required.
• Use a scan tool to attempt communication with the EPB ECU and other modules on same bus.

Signal parameters

• Battery supply to EPB ECU: nominal 11–14 V with ignition on; no large voltage drops during attempts.
• CAN bus idle voltages (typical): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V.
• CAN dominant bit voltages (typical): CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V when driven.
• Termination resistance across CAN H-L: approx. 60 Ω (two 120 Ω terminators in parallel).
• Expected ECU response: ECU should appear on the network and respond to diagnostic requests; if absent, no replies are returned.

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