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Home / DTC / U040C — Invalid Data Received From Exhaust Gas Recirculation Control Module “B”

U040C — Invalid Data Received From Exhaust Gas Recirculation Control Module “B”

Detailed page for trouble code U040C.

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22,461specific
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Code

U040C

HYUNDAI U — Network/User

Invalid Data Received From Exhaust Gas Recirculation Control Module “B”

Brand: HYUNDAI
Type: U — Network/User
Views: UK: 23 EN: 32 RU: 30
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Page language: EN

Causes

  • Faulty EGR Control Module “B” (hardware or corrupted firmware)
  • Open/short/corroded wiring or connector at the EGR Control Module “B”
  • Poor module power or ground (low battery voltage, blown fuse, poor chassis/ground connection)
  • CAN bus wiring fault (short to Vbatt/GND, high resistance, broken shield, poor termination)
  • Multiple modules causing bus errors or CAN bus overload/noise
  • Software mismatch or incorrect/reflashed ECU calibration

Symptoms

  • Malfunction Indicator Lamp (MIL) or check engine light illuminated
  • EGR-related functions disabled or defaulted by powertrain control module
  • Reduced engine performance, rough idle, or increased NOx emissions (depending on how the ECU responds)
  • Related DTCs for EGR or CAN-bus devices present
  • Possible intermittent or permanent drivability issues (hesitation, reduced fuel economy)

What to check

  • Read all stored and pending codes and freeze frame with a capable scan tool; note related U- and P-codes
  • Verify the vehicle’s network topology and whether EGR Control Module “B” is present and responsive on the scan tool
  • Visually inspect EGR Control Module connector and wiring for corrosion, bent pins, or damage
  • Check fuses and relays feeding the EGR module power circuit
  • Measure module supply voltage and ground integrity at the connector with ignition ON
  • Scan for other modules that report CAN bus errors or that are not present

Signal parameters

  • Module presence: module ID/ECU address on CAN bus (should respond to diagnostic tool)
  • EGR messages typically include EGR valve commanded position, actual position/feedback, temperature, and status bytes
  • Message frequency: many module status frames are 5–20 Hz (varies by vehicle)
  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); during dominant bits CAN_H ≈ 3.5 V and CAN_L ≈ 1.5 V
  • Bus error counters and transmit/receive error frames (tool dependent)

Diagnostic algorithm

  1. Record full scan results (all U- and P-codes) and freeze frame; note whether the code is current or historic.
  2. Inspect EGR Control Module “B” connector and wiring harness for damage, corrosion, or water intrusion; repair any damage.
  3. Verify battery voltage is within specification; check and replace any blown fuses related to the EGR module power supply.
  4. With ignition ON, measure module supply voltage and ground at the connector. Repair poor power/ground connections before proceeding.
  5. Use a scan tool to verify the EGR module appears on the network and can be polled. If the module is not present, suspect power/ground/wiring or module failure.
  6. Check for other modules showing communication issues; if widespread, troubleshoot CAN bus (look for shorts to battery/ground, damaged wiring, missing termination).
  7. If bus presence is intermittent or noise is suspected, capture CAN waveforms with an oscilloscope. Confirm CAN_H and CAN_L waveforms are within expected amplitude and timing.
  8. Back-probe or wiggle-test the harness while monitoring network messages to locate intermittent breaks.
  9. If wiring and bus integrity are confirmed, attempt a controlled reflash or calibration update of the EGR module per manufacturer procedure (some modules require matching or reprogramming after replacement).
  10. If diagnostics point to the EGR Control Module “B” as failed, replace the module and follow any required initialization/relearn procedures. Re-scan and road test to confirm the code does not return.
  11. If the code persists after replacement and reprogramming, escalate to detailed network analysis or dealer-level diagnostics to check gateway/ECU communication and software versions.

Likely causes

  • Intermittent or corroded connector at EGR Control Module “B”
  • Failed or unresponsive EGR Control Module “B”
  • CAN bus wiring short or open between the EGR module and main ECU/gateway
  • Blown fuse or bad ground to EGR module causing faulty transmissions
  • Software/calibration mismatch after module replacement or update

Fault status

⚠️ Status
Invalid data received from Exhaust Gas Recirculation Control Module “B” — CAN network message invalid, missing, or corrupted; verify module, power/ground, wiring, and bus integrity.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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