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Home / DTC / U041C — Invalid Data Received From Rocker Arm Control Module “A”

U041C — Invalid Data Received From Rocker Arm Control Module “A”

Detailed page for trouble code U041C.

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59brands
11,925generic
22,548specific
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Code

U041C

HYUNDAI U — Network/User

Invalid Data Received From Rocker Arm Control Module “A”

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

Causes

  • Loss or corruption of CAN/LIN network messages between the Rocker Arm Control Module and the PCM
  • Open/short/poor connection in wiring harness or connector to the rocker arm module
  • Insufficient or intermittent power supply or ground to the rocker arm control module
  • Failed Rocker Arm Control Module (internal electronics or firmware)
  • PCM or other module software mismatch or need for reflash
  • Damage from moisture, corrosion or physical impact at connector/module

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Reduced engine performance or limp mode (engine derate)
  • Erratic idle, hesitation, or rough running
  • VVT/rocker arm actuation disabled or not functioning correctly
  • Possible diagnostic communication errors with other modules
  • Decreased fuel economy or increased emissions

What to check

  • Connect a capable scan tool, read all stored and pending codes, and capture freeze-frame and live data
  • Check for related communication codes (U0100, U0073, U0121 etc.) and module presence on the network
  • Visually inspect rocker arm control module connector and wiring for corrosion, bent pins, or damage
  • Verify fuses and relays powering the rocker arm module and PCM
  • Verify battery voltage and chassis/engine grounds are clean and tight
  • Use an oscilloscope or quality scan tool to monitor CAN bus signals and message rates

Signal parameters

  • CAN bus recessive voltage typically ~2.5 V on CANH and CANL; dominant state shows expected differential (approx. CANH ~3.5V, CANL ~1.5V) — verify with scope
  • Expected message/update rate: module messages typically update multiple times per second (>= ~5–10 Hz) — confirmed with scan tool
  • Module supply: stable battery voltage (~12 V) present at module harness pin with ignition ON
  • Ground: low-impedance ground at module body/ground pin (milliohms to a few ohms)
  • Rocker arm position/feedback sensor signals typically 0–5 V (model dependent); commanded vs actual position should be within small tolerance (few degrees or a small voltage difference)

Diagnostic algorithm

  1. Retrieve and record all DTCs and freeze-frame data; note whether U041C is current, pending, or historical.
  2. Check for other communication-related codes (U0100, U0073, U0121, U0415 etc.) that indicate network problems.
  3. With ignition ON (engine off), verify module presence with a scan tool (can the rocker arm control module be accessed?).
  4. Visually inspect the rocker arm control module connector, wiring harness, and nearby harness for damage, corrosion, chafing or rodent damage.
  5. Verify fuses/relays and check for proper battery voltage at the module power pin; verify a good ground at module ground pin.
  6. Using a scan tool or scope, monitor CANH/CANL voltages and message traffic while cycling ignition and during cranking; look for missing messages, bus errors, or abnormal voltage levels.
  7. Wiggle test wiring and connectors while monitoring bus and module presence to try to reproduce the fault.
  8. If wiring and power/grounds are good, update PCM and rocker arm module software per manufacturer and re-check communication.
  9. If communication remains invalid and wiring/power/grounds verified, consider replacing the rocker arm control module; confirm with a known-good module swap if available.
  10. After repair, clear codes, perform relearns or calibrations required by the manufacturer, and confirm repair with road test and re-scan.

Likely causes

  • Corroded or loose connector pins at the rocker arm control module
  • Broken or shorted CAN-H / CAN-L wiring near the engine harness
  • Module lost battery power during a software update or jump-start, leaving corrupted data
  • Failed rocker arm control module (intermittent internal communication fault)
  • Faulty PCM interpreting valid messages due to software issue or memory error

Fault status

⚠️ Status
Stored when the vehicle’s control module receives invalid, implausible, or corrupted data from the Rocker Arm Control Module “A” or when communication integrity (checksum/message format) fails. May be intermittent if caused by wiring or connector issues, or permanent if module hardware/firmware is faulty.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

U0100 U0073 U0121 U0415
371

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