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Home / DTC / U0151 — Lost Communication With Restraints Control Module

U0151 — Lost Communication With Restraints Control Module

Detailed page for trouble code U0151.

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Code

U0151

HYUNDAI U — Network/User

Lost Communication With Restraints Control Module

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • RCM (SRS module) powered down, damaged, or internally failed
  • Blown fuse or loss of module supply/ignition feed
  • Open, short or high-resistance in CAN wiring (CAN High/CAN Low) or connectors
  • Poor or missing ground connection for the RCM
  • Damaged or corroded module connector pins
  • Aftermarket device or poor repair affecting the CAN bus

Symptoms

  • SRS / airbag warning lamp illuminated or flashing
  • Inability to communicate with RCM using a scan tool
  • Other modules report lost communication with RCM
  • Possible disablement of seatbelt pretensioners or other restraint functions
  • Stored U0151 (may be accompanied by other U0xxx network codes)
  • Some vehicle safety diagnostics or functions unavailable

What to check

  • Use scan tool: read all U0xxx and B/P codes, note freeze frame and related communication faults
  • Attempt to communicate with RCM; confirm 'no response' or timeouts
  • Check battery voltage (should be 12.6V+ at rest; >11V while cranking) and charging system
  • Inspect SRS/RCM fuses and ignition feed fuses; verify voltage at fuse terminals with ignition ON
  • Visually inspect RCM connector and wiring for corrosion, bent pins, water, or physical damage
  • Check RCM ground(s) for continuity to chassis and engine ground; measure

Signal parameters

  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive). Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (values approximate)
  • Expected CAN bus termination: ~60 ohms between CAN_H and CAN_L (two 120 ohm resistors in parallel)
  • Battery supply to RCM: nominal 12 V (measure at module power pin with ignition ON/ACC as required)
  • Ground continuity: module ground to chassis ideally
  • Module response: RCM should respond to standard SRS/CAN request frames from scan tool; absence indicates lost comms

Diagnostic algorithm

  1. Step 1 — Safety: Follow Hyundai SRS safety procedure before working on restraints. Disable battery (negative terminal) and wait the manufacturer-specified time before disconnecting SRS connectors.
  2. Step 2 — Scan and record: With scan tool, record U0151 and any related U0xxx or B/P codes and freeze-frame data. Note whether RCM is listed on module list.
  3. Step 3 — Basic electrical: Check battery voltage and condition. Verify SRS and relevant ignition fuses have continuity and proper voltage at fuse holder with ignition ON.
  4. Step 4 — Visual inspection: Inspect RCM connector, harness, and nearby wiring for damage, corrosion, water intrusion or signs of a prior deployment repair.
  5. Step 5 — Grounds and power: Verify proper power and ignition feeds at RCM power pins and verify a good chassis ground at RCM mounting point.
  6. Step 6 — Network verification: Check CAN bus physical layer — measure CAN_H/CAN_L idle voltages and termination resistance (~60 ohms). If voltages or termination are wrong, trace wiring for shorts or opens.
  7. Step 7 — Module communication: Use a CAN sniffer or oscilloscope to look for RCM message IDs on the bus. If no frames, verify surrounding modules and junction connectors for continuity.
  8. Step 8 — Isolate: If suspected wiring fault, disconnect other modules or splice connectors to isolate the section of bus. Repair any damaged wiring or replace connectors as required.
  9. Step 9 — Replace or reflash: If wiring and power/ground are good but RCM does not respond, consider module replacement or reprogramming per Hyundai service procedures (do not install a used RCM unless properly cleared/reprogrammed).
  10. Step 10 — Verify: After repairs, reconnect battery, clear codes, then perform vehicle self-tests and road/functional test. Confirm SRS lamp behavior and that U0151 does not return.
  11. Step 11 — Post-repair: If module replacement was necessary, ensure proper configuration and any required CODING/INITIALIZATION is performed according to Hyundai service information.

Likely causes

  • Loose or corroded connector at the RCM
  • Faulty RCM hardware or water ingress
  • Blown SRS or CAN-related fuse
  • Broken or shorted CAN wire between RCM and vehicle network
  • Bad ground strap at RCM mounting point
  • Intermittent network connector causing loss of frames

Fault status

⚠️ Status
Lost communication with Restraints Control Module (RCM/SRS) — no response on CAN bus
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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