Code
U1000
DS
U — Network/User
Electric parking brake ECU not communicating fault: Not characterised
Views:
UK: 1
EN: 1
RU: 1
AI status
Completed
Completed
100%
Causes
- Open or short in CAN bus wiring (CAN High / CAN Low)
- Corroded or loose connector at EPB ECU or junctions
- Blown fuse or lost power/ground to EPB ECU
- Failed EPB ECU (internal fault)
- Network termination missing or incorrect
- Low battery or unstable supply voltage
Symptoms
- EPB warning lamp or generic communication warning on dash
- Parking brake unable to engage or release via switch
- Central electrics/service message: 'Electric parking brake fault' or 'Service required'
- Related features (hill hold, auto-release) not functioning
- Scan tool cannot communicate with EPB module or shows 'no response'
- Intermittent or permanent loss of related diagnostic data
What to check
- Read and record all stored U and B codes from all control modules
- Verify battery voltage is within specification (typically >12.4 V) and good battery health
- Inspect fuses and relays powering the EPB ECU
- Visually inspect EPB ECU connector and CAN harness for corrosion, bent pins, damage or water ingress
- Check for other modules reporting CAN bus errors (helps locate network segment)
- Use a scan tool to monitor network traffic and confirm whether the EPB sends/receives messages
Signal parameters
- CAN High (idle/recessive): ≈ 2.5 V
- CAN Low (idle/recessive): ≈ 2.5 V
- Dominant state differential: up to ≈ 2.0 V between CAN_H and CAN_L
- Typical bus termination: ~60 ohms across CAN_H and CAN_L (two 120 Ω in parallel)
- Common data rates: 500 kbps or 250 kbps (verify vehicle-specific rate with tool/oscilloscope)
- Active bus waveform visible with oscilloscope; absence of activity indicates module not transmitting
Diagnostic algorithm
- Record freeze frame and all related codes. Note when the fault is present (key on/off, driving, after wash).
- Check battery voltage and charge if required. Re-test after ensuring stable supply.
- Inspect and secure ground and power connections to EPB ECU; verify supply voltage at ECU connector with key on.
- Check fuses/relays for EPB circuit; replace if blown and re-check communication.
- Scan other modules to determine whether the fault is isolated to EPB or a wider network issue.
- Use scan tool to attempt communication with EPB; if no response, clear codes and attempt to reproduce the fault.
- Visually inspect EPB connector and harness for damage, corrosion or water ingress; repair as needed.
- Perform continuity and short tests on CAN_H and CAN_L between EPB connector and gateway/ABS/BCM nodes. Repair any opens/shorts.
- Measure CAN bus resistance between H and L (expect ~60 Ω). If not present, check termination resistors and wiring.
- Use an oscilloscope to observe CAN_H and CAN_L for valid waveforms and activity while other modules are communicating.
- If bus is being held dominant or noise is present, isolate segments by disconnecting connectors/modules one at a time to locate faulty node.
- If wiring, connectors and power/ground are good and the module still does not communicate, consider reprogramming or replacement of EPB ECU per manufacturer procedures.
Likely causes
- Damaged CAN pair between EPB ECU and main vehicle CAN backbone
- Poor ground or power feed to the EPB ECU preventing wake-up or transmission
- Connector pin corrosion or bent pins at EPB connector
- Failed EPB ECU hardware or internal communications interface
- Short to battery or ground on CAN_H or CAN_L due to a harness chafe
Fault status
Status
No response from Electric Parking Brake ECU on vehicle network — communication lost.
Repair difficulty: Medium
Diagnostic time: 1.5 - 4.0 hours
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