Code
U2000
CITROEN
U — Network/User
Fault in reception of the main wake-up / triggering request information on the CAN: Absence of signal or data invalid
Views:
UK: 5
EN: 8
RU: 9
AI status
Completed
Completed
100%
Causes
- Open, shorted or high‑resistance CAN wiring or connectors
- Missing or intermittent module power or ground
- Faulty or unresponsive sending module (BCM, BCM gateway, ignition module)
- Failed or out‑of‑date module software/calibration
- Weak battery or low system voltage preventing wake signals
- Missing or incorrect bus termination (open/misaligned 120 Ω)
Symptoms
- No communication with one or more modules on scan tool
- Modules failing to wake after door unlock or ignition on
- Central locking, remote functions or convenience features inoperative
- Instrument cluster or body systems not responding or delayed
- Intermittent faults or multiple communication DTCs present
- Vehicle enters reduced functionality or fails to start if keyless wake fails
What to check
- Confirm U2000 present and note freeze frame / related codes
- Check battery voltage at rest and during wake attempt (12.4–12.8 V nominal; >11.5 V while cranking)
- Inspect fuses and power/ground at modules involved in wake logic (BCM, gateway)
- Visually inspect CAN wiring, connectors and junctions for damage or corrosion
- Measure CAN_H and CAN_L voltages with key off and key on using a multimeter and oscilloscope
- Measure bus differential with oscilloscope to verify dominant/recessive transitions
Signal parameters
- Idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ~2.0 V)
- Termination: combined end-to-end ≈ 60 Ω (two 120 Ω in parallel)
- Wake request: periodic message on CAN or dedicated wake line — timing and ID model-specific (verify with OEM data)
- Low battery condition: voltage
Diagnostic algorithm
- Read and record all DTCs and freeze frame data. Note related U codes.
- Verify vehicle battery condition and charging system; recharge or replace battery if low.
- Inspect wiring and connectors for physical damage, corrosion or water ingress at gateway/BCM and CAN junctions.
- Check fuses and module power/ground circuits; measure supply voltage at module connectors during wake attempt.
- With a good oscilloscope or CAN analyzer, capture CAN_H/CAN_L while attempting a wake to confirm presence/quality of wake message and look for noise or missing frames.
- Measure termination resistance between CAN_H and CAN_L at harness; repair or replace missing/incorrect termination.
- Isolate sections: disconnect non‑essential modules or branch connectors to locate short or faulted node causing invalid frames.
- If physical layer and power/ground are good, check for software/calibration updates for gateway/BCM and reflash or replace module per OEM procedure.
- After repairs, clear codes and perform functional verification of wake events and full system communication; road test if required.
- If the fault persists, consult manufacturer technical bulletins and consider module replacement only after confirming diagnostics.
Likely causes
- Damaged CAN physical layer (broken conductor or short to battery/ground)
- Faulty body control/gateway module that generates the wake request
- Blown fuse or poor power/ground to the module that listens for wake message
- Disconnected or corroded connector at relevant control module
- Battery voltage too low at ignition-off or during wake attempt
Fault status
Status
Main CAN wake/trigger message not received or data invalid. The control unit did not detect a valid wake request on the network, preventing normal communication and module wake-up.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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