Code
U1542
HYUNDAI
U — Network/User
Wakeup Line Test Failed at MTS(Mozen) Unit
Views:
UK: 17
EN: 30
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or short in wakeup wiring between MTS and Body Control Module (BCM) or wake driver
- Poor connector pin contact or corrosion at MTS connector or intermediate junctions
- Blown fuse or loss of power/ground to MTS or wake circuit
- Faulty BCM, gateway module, or other module that drives the wakeup line
- Defective MTS (internal fault) or failed wakeup circuitry inside the unit
- Incorrect or outdated software/calibration causing false test failure
Symptoms
- DTC U1542 stored in MTS and/or vehicle network gateway
- MTS functions (telematics/remote features) not responding or not waking
- No communication with MTS on diagnostic tester
- Possible battery drain or failure to enter sleep/wakeup states correctly
- Accessory functions tied to MTS may be unavailable
What to check
- Read freeze frame and full UDS/CAN diagnostic data with OEM scan tool
- Verify battery voltage (12.6 V nominal, >11.8 V during cranking tests) and charging system
- Inspect fuses and relays related to MTS and BCM power/wakeup circuits
- Visually inspect MTS connector, pins and harness for corrosion, damage or water intrusion
- Check for related communication U-codes (CAN/LIN faults) in BCM/Gateway
- Measure wakeup line voltage/logic state at MTS connector while performing wake attempts
Signal parameters
- Wakeup line logic: inactive and active states vary by design — typically low (≈0 V) vs pulled high (≈12 V) or vice versa; consult service manual for exact thresholds
- CAN bus idle voltage ~2.5 V per line (differential behavior) — communication should be present if bus awake
- LIN wake pulse: single pulse on LIN line or diode-driven wake pattern — verify with oscilloscope
- Battery voltage must be within nominal range for valid wakeup sequence
Diagnostic algorithm
- Connect OEM scan tool, confirm U1542 and any additional codes. Record conditions and freeze frame data.
- Clear codes, attempt to reproduce with known wake method (remote lock/unlock, key on, scan tool wake). Note behavior.
- Verify battery voltage and charging system. Recharge or replace battery if low and retest.
- Inspect MTS connector and harness for damage/corrosion. Repair any physical faults and ensure secure connector seating.
- With ignition off, measure continuity and resistance of wakeup wire between MTS and BCM/gateway. Check for shorts to ground or battery.
- Probe wakeup line while performing wake request (use oscilloscope if available) to confirm proper signal transitions per service manual.
- Verify power and ground at MTS pins under load; wiggle harness to detect intermittent faults.
- Check BCM/gateway outputs and message traffic on CAN/LIN during wake attempt. Replace or reflash BCM/gateway only if confirmed faulty.
- If wiring and related modules are good, follow OEM procedure to reflash or replace MTS unit. After repairs, clear codes and perform full system wake/sleep verification.
- Document findings; if intermittent, perform extended soak/sleep tests to confirm repair.
Likely causes
- Damaged harness or pin corrosion at MTS connector
- BCM/wakeup driver not asserting wake signal due to fault or config
- Intermittent ground or poor power supply to MTS
- Software mismatch or ECU programming error
Fault status
Status
Wakeup Line Test Failed at MTS unit — module did not detect expected wakeup signal.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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