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Home / DTC / U0442 — Invalid Data Received From ECM/PCM “B”

U0442 — Invalid Data Received From ECM/PCM “B”

Detailed page for trouble code U0442.

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U0442

HYUNDAI U — Network/User

Invalid Data Received From ECM/PCM “B”

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

Causes

  • Open, short, or high resistance in CAN/communication wiring or connectors
  • Corroded, loose, or damaged ECM/PCM connector pins
  • Intermittent power (battery) or poor ground to ECM/PCM or other modules
  • Faulty ECM/PCM hardware or internal software corruption
  • Incompatible or outdated module software/calibration
  • Interference or conflict from aftermarket electronics (alarms, tuners, modules)

Symptoms

  • Malfunction Indicator Lamp (MIL) or other warning lights illuminated
  • Loss or intermittent loss of functions controlled by the ECM (engine management, limp mode)
  • Inability of scan tool to communicate with ECM or inconsistent module data
  • Erratic instrument cluster readings (RPM, speed, gauges) or drivability issues
  • Random or repeatable communication-related DTCs present

What to check

  • Read all stored, pending and freeze-frame data with an OEM-capable scan tool; record module presence and related U-codes
  • Verify battery voltage at rest and during cranking (should be >12.2 V at rest; >10 V while cranking)
  • Visually inspect ECM/PCM connector and nearby harness for damage, corrosion, moisture, or bent pins
  • Check main power and ground connections to ECM/PCM for proper resistance and tightness
  • Check CAN_H and CAN_L voltage at ECM connector with key ON, engine OFF (both near ~2.5 V idle)
  • Measure CAN differential waveform with a scope while communicating (look for noise, missing frames, dominant stuck states)

Signal parameters

  • Battery voltage (key ON and cranking)
  • ECM presence/ID and module response time to scan tool requests
  • Engine RPM and throttle position values reported by ECM
  • Vehicle speed and transmission inputs (if present)
  • CAN_H and CAN_L voltages at ECM connector (idle ~2.5 V each)
  • CAN differential voltage and waveform quality (observe frames, bit errors)

Diagnostic algorithm

  1. Connect an OEM diagnostic scanner and read all DTCs and freeze-frame data; note any other U-codes or related module faults.
  2. Verify battery voltage and main grounds at the ECM; repair loose or corroded connections. Clear codes and retest.
  3. Visually inspect ECM connector and harness for corrosion, bent pins, or water damage; repair/replace damaged connectors or harness sections as required.
  4. Check CAN bus idle voltages at ECM connector (CAN_H and CAN_L ~2.5 V). If voltages are abnormal, isolate wiring to find short/high resistance.
  5. Measure termination resistance across CAN_H and CAN_L at two ends of the network (approx. 60 ohms). Repair missing or incorrect terminators.
  6. Use an oscilloscope to observe CAN differential waveform while exercising modules; look for noise, missing messages, or a stuck dominant state.
  7. Perform wiggle/strain tests on harnesses and connectors while monitoring for communication dropouts; repair intermittent wiring faults.
  8. Inspect and disconnect aftermarket devices that share the CAN bus and re-check communication.
  9. If wiring and connectors check good, verify ECM software/calibration level and apply any applicable updates or reflash the ECM per manufacturer procedure.
  10. If reprogramming does not clear the issue and wiring/terminations are good, replace the ECM/PCM only after verifying with manufacturer diagnostics and following module programming and relearn procedures. Clear codes and perform a full road test.

Likely causes

  • Corroded/loose ECM connector or pin damage
  • Damaged or chafed CAN wiring between ECM and network junctions
  • Low battery voltage or poor engine bay ground causing data corruption
  • Outdated or mismatched ECM software after replacement/repair
  • Aftermarket device interfering on the CAN bus

Fault status

⚠️ Status
Invalid data received from ECM/PCM 'B' — communication/data integrity fault on vehicle network; inspect CAN wiring, connectors, power/grounds, and ECM software.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

U0401 U0100 U0101 U0121 U0141
371

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