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Home / DTC / U04A4 — Invalid Data Received From Particulate Matter Sensor A

U04A4 — Invalid Data Received From Particulate Matter Sensor A

Detailed page for trouble code U04A4.

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U04A4

Generic U — Network/User

Invalid Data Received From Particulate Matter Sensor A

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 30 RU: 14
AI status
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Page language: EN

Causes

  • Open, short, or intermittent wiring to PM sensor A (power, ground, signal)
  • Poor connector contact or corrosion at the sensor or harness
  • Failed or degraded particulate matter sensor (contamination, internal fault)
  • Heater element failure or incorrect heater resistance (if equipped)
  • CAN/LIN or dedicated serial communication errors or bus faults
  • ECU/module software fault or calibration mismatch

Symptoms

  • U04A4 stored in memory; related PM/DPF monitoring warnings
  • Malfunction indicator lamp (MIL) or DPF/PM warning message on dash
  • Reduced engine performance or forced regen behavior (depending on strategy)
  • DPF regeneration may not complete or may be inhibited
  • Inconsistent or implausible PM readings on a scan tool (e.g., out-of-range values, spikes, NaN)

What to check

  • Read all stored and pending codes; record freeze frame and related DTCs
  • Check live PID/parameter for PM sensor A; note value, update rate, and plausibility
  • Inspect sensor connector for corrosion, bent pins, water intrusion, or damage
  • Visually inspect wiring harness for chafing, breaks, or repairs near sensor and ECU
  • Verify sensor supply voltage and ground at connector with key on (voltage and continuity)
  • Scan for CAN/LIN bus errors, bus load, and check other modules for communication issues

Signal parameters

  • Sensor output type: analog voltage (typical 0–5.0 V) or digital/CAN message (varies by vehicle)
  • Expected steady-state analog range: ~0.1–4.9 V (specific range depends on sensor design)
  • Heater resistance (if equipped): measure ohms against manufacturer spec; open or short indicates fault
  • Signal update rate: typically 0.5–10 Hz for CAN PM messages; analog sample rates vary
  • CAN/LIN: valid message ID and data length; check for frequent retransmissions or error frames

Diagnostic algorithm

  1. Retrieve and record all DTCs, freeze frame and live PM sensor data with a capable scan tool.
  2. Inspect connector and wiring at PM sensor A for corrosion, water ingress, damaged pins, or loose latch; clean and reseat connector.
  3. With key ON engine OFF, verify sensor supply voltage and ground at the connector against specification. Repair wiring if supply/ground missing or out of range.
  4. Probe the sensor signal with a multimeter or oscilloscope while observing live data on scan tool. Look for stuck, noisy, intermittent, or out-of-range readings.
  5. If sensor has a heater, disconnect power and measure heater resistance; compare to spec. Check heater supply and switching by ECU during test regen/command.
  6. Check CAN/LIN network: verify other modules respond, check for bus faults, and confirm the PM sensor’s CAN ID/messages appear and update. Repair bus faults (terminators, shorts) if present.
  7. Perform a wiggle test on wiring and connector while monitoring live data to find intermittent faults.
  8. If wiring and communication are good but sensor output is implausible or fails bench tests, replace PM sensor A and retest.
  9. After repair, clear codes and perform a road test or required DPF/PM functional tests and ensure code does not return. Verify any required relearn/calibration procedures.
  10. If problem persists after sensor replacement, consider ECU/software update or module testing/reprogramming per manufacturer guidance.

Likely causes

  • Corroded or loose connector at PM sensor A
  • Damaged wiring harness (rodent chew, abrasion, pinch)
  • Contaminated or saturated sensor from prolonged DPF/PM exposure
  • Failed internal electronics inside the PM sensor (common over time)
  • Intermittent CAN bus frame(s) or termination problem

Fault status

⚠️ Status
Control module detected invalid or out-of-range data from Particulate Matter Sensor A.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

U0401 U0415 U0416 U0420 P0496
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