Code
U041C
Generic
U — Network/User
Invalid Data Received From Rocker Arm Control Module A
AI status
Completed
Completed
100%
Causes
- Intermittent or failed communication on CAN/LIN network between PCM/scan tool and Rocker Arm Control Module A
- Damaged wiring harness, broken or corroded connector pins at the rocker arm control module
- Poor power or ground to the rocker arm control module
- Faulty rocker arm control module (internal electronics/software)
- Wrong or incompatible module programming or calibration
- Missing or improper network termination (open/incorrect resistor)
Symptoms
- MIL/CEL illuminated and U041C stored
- Reduced engine performance or limp-home operation (if rocker arm control is essential)
- Irregular valve timing, rough idle, or misfire-like behavior
- Intermittent faults that may come and go with vibration or temperature changes
- Multiple network U-codes present (loss of comms to other modules)
What to check
- Connect a capable scan tool, read DTCs and freeze frame; note whether code is current or historic
- Check for other U-codes and modules reporting communication errors
- Visual inspection of wiring and connectors at the rocker arm control module and along the harness
- Verify battery voltage and key-on power to the module (check fuses and relays)
- Check module grounds for tightness and corrosion
- Measure CAN/LIN bus voltages with a DMM and compare to expected idle levels
Signal parameters
- CAN bus idle voltages: CANH ≈ 2.5V, CANL ≈ 2.5V (recessive); dominant state: CANH ≈ 3.5V, CANL ≈ 1.5V
- Expected CAN bus termination: ~60 ohms between CANH and CANL
- Message frequency: module-specific (often periodic updates between 1–20 Hz); verify expected ID(s) present with a CAN sniffer
- LIN bus idle ≈ single-wire ~12V (or module specific); check LIN wake/pulse patterns if applicable
- Error frames or corrupted frames visible on an oscilloscope/CAN log indicate network integrity problems
Diagnostic algorithm
- Retrieve and record all DTCs and freeze-frame data; note if U041C is current or intermittent.
- Look for associated U-codes or B/C codes that show network-wide problems.
- Perform a thorough visual inspection of connector(s) at the rocker arm control module for corrosion, bent pins, pushed-out terminals, or water intrusion; repair as needed.
- Verify module supply and grounds with a DMM (battery voltage at power pin with key ON,
- Check CAN/LIN bus voltages at the module connector with key ON; compare to expected signal parameters.
- Use a CAN sniffer or oscilloscope to confirm the rocker arm control module’s CAN ID/messages are present and not corrupted; look for missing messages, error frames, or abnormal voltages.
- Wiggle wiring/harness while monitoring live data to reproduce intermittent communication faults.
- Inspect and measure CAN termination resistance (approx. 60 ohms). Remove modules one at a time only if instructed by manufacturer procedures.
- If wiring and bus integrity are confirmed, verify module software/calibration level and reflash or update according to OEM procedure; follow safety and anti-theft/programming instructions.
- Replace the rocker arm control module only after eliminating harness/network causes. After replacement, program/configure the new module per manufacturer instructions and clear codes, then retest for recurrence.
- If problem persists, consult manufacturer technical service information and wiring diagrams or escalate to a specialist with advanced network diagnostic tools.
Likely causes
- Connector corrosion or bent pins at the rocker arm control module
- Open/short in CAN high/low or LIN bus between modules
- Defective rocker arm control module
- PCM/software mismatch — module needs reprogramming or calibration
- Missing 60 ohm termination or multiple terminations on the bus
Fault status
Status
Invalid data or corrupted messages received from Rocker Arm Control Module A. May be stored as current or intermittent; likely a communication, wiring, power/ground, or module software/hardware fault.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U041C
HYUNDAI
U — Network/User
Invalid Data Received From Rocker Arm Control Module “A”
AI status
Completed
Completed
100%
Causes
- Intermittent or failed communication on CAN/LIN network between PCM/scan tool and Rocker Arm Control Module A
- Damaged wiring harness, broken or corroded connector pins at the rocker arm control module
- Poor power or ground to the rocker arm control module
- Faulty rocker arm control module (internal electronics/software)
- Wrong or incompatible module programming or calibration
- Missing or improper network termination (open/incorrect resistor)
Symptoms
- MIL/CEL illuminated and U041C stored
- Reduced engine performance or limp-home operation (if rocker arm control is essential)
- Irregular valve timing, rough idle, or misfire-like behavior
- Intermittent faults that may come and go with vibration or temperature changes
- Multiple network U-codes present (loss of comms to other modules)
What to check
- Connect a capable scan tool, read DTCs and freeze frame; note whether code is current or historic
- Check for other U-codes and modules reporting communication errors
- Visual inspection of wiring and connectors at the rocker arm control module and along the harness
- Verify battery voltage and key-on power to the module (check fuses and relays)
- Check module grounds for tightness and corrosion
- Measure CAN/LIN bus voltages with a DMM and compare to expected idle levels
Signal parameters
- CAN bus idle voltages: CANH ≈ 2.5V, CANL ≈ 2.5V (recessive); dominant state: CANH ≈ 3.5V, CANL ≈ 1.5V
- Expected CAN bus termination: ~60 ohms between CANH and CANL
- Message frequency: module-specific (often periodic updates between 1–20 Hz); verify expected ID(s) present with a CAN sniffer
- LIN bus idle ≈ single-wire ~12V (or module specific); check LIN wake/pulse patterns if applicable
- Error frames or corrupted frames visible on an oscilloscope/CAN log indicate network integrity problems
Diagnostic algorithm
- Retrieve and record all DTCs and freeze-frame data; note if U041C is current or intermittent.
- Look for associated U-codes or B/C codes that show network-wide problems.
- Perform a thorough visual inspection of connector(s) at the rocker arm control module for corrosion, bent pins, pushed-out terminals, or water intrusion; repair as needed.
- Verify module supply and grounds with a DMM (battery voltage at power pin with key ON,
- Check CAN/LIN bus voltages at the module connector with key ON; compare to expected signal parameters.
- Use a CAN sniffer or oscilloscope to confirm the rocker arm control module’s CAN ID/messages are present and not corrupted; look for missing messages, error frames, or abnormal voltages.
- Wiggle wiring/harness while monitoring live data to reproduce intermittent communication faults.
- Inspect and measure CAN termination resistance (approx. 60 ohms). Remove modules one at a time only if instructed by manufacturer procedures.
- If wiring and bus integrity are confirmed, verify module software/calibration level and reflash or update according to OEM procedure; follow safety and anti-theft/programming instructions.
- Replace the rocker arm control module only after eliminating harness/network causes. After replacement, program/configure the new module per manufacturer instructions and clear codes, then retest for recurrence.
- If problem persists, consult manufacturer technical service information and wiring diagrams or escalate to a specialist with advanced network diagnostic tools.
Likely causes
- Connector corrosion or bent pins at the rocker arm control module
- Open/short in CAN high/low or LIN bus between modules
- Defective rocker arm control module
- PCM/software mismatch — module needs reprogramming or calibration
- Missing 60 ohm termination or multiple terminations on the bus
Fault status
Status
Invalid data or corrupted messages received from Rocker Arm Control Module A. May be stored as current or intermittent; likely a communication, wiring, power/ground, or module software/hardware fault.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Repair manuals
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