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Home / DTC / U0644 — Lost Communication With Wastegate Position Sensor A

U0644 — Lost Communication With Wastegate Position Sensor A

Detailed page for trouble code U0644.

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U0644

Generic U — Network/User

Lost Communication With Wastegate Position Sensor A

Brand: Generic
Type: U — Network/User
Views: UK: 15 EN: 25 RU: 17
AI status
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ready
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Page language: EN

Causes

  • Open or shorted wiring between wastegate position sensor and control module
  • Faulty wastegate position sensor (analog potentiometer or sensor module)
  • Poor or corroded connector pins or connector not fully seated
  • Loss of reference voltage or ground to the sensor
  • Fault on vehicle communication bus (CAN or LIN) or bad termination
  • Intermittent wiring (chafing, corrosion, heat damage)

Symptoms

  • Malfunction indicator lamp (MIL) or check engine light illuminated
  • Reduced engine power, turbo overboost or limp-home mode
  • Erratic turbo behavior or turbo stuck at certain position
  • No wastegate position data available in scan-tool live data
  • Intermittent fault codes or related network U-codes present

What to check

  • Read and record stored/active DTCs and freeze frame data; note any related U- or P-codes
  • Visually inspect wiring and connector at the wastegate position sensor for damage, corrosion, or loose pins
  • Check that the sensor connector is fully seated
  • Use a scan tool to look for live wastegate sensor data and check if the module for that sensor is present on the network
  • Backprobe sensor connector and verify reference voltage and ground with ignition ON
  • Measure sensor signal voltage while moving wastegate (if accessible) to verify changing signal

Signal parameters

  • Sensor reference voltage (typical): ~5.0 V (verify OEM spec)
  • Sensor signal range (typical analog potentiometer): ~0.5–4.5 V across travel (varies by design)
  • Sensor resistance (if potentiometer): typically 1–10 kΩ (check OEM spec)
  • CAN bus idle voltages (typical): CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V; differential ≈ 0 V idle, ≈ 2 V dominant
  • LIN bus (if used): single-wire idle near battery voltage; active pulls low (verify vehicle-specific)

Diagnostic algorithm

  1. Retrieve and save all codes and freeze frame data. Note other network U-codes or related P-codes.
  2. Inspect the wastegate position sensor connector and wiring harness for physical damage, corrosion, rodent damage, or unsecured routing. Repair as needed.
  3. With ignition ON (engine off), backprobe the sensor connector: verify reference voltage and ground presence. If reference or ground missing, trace to power/ground source and repair.
  4. Check the sensor signal pin voltage while slowly moving the wastegate actuator (or have an assistant cycle throttle if needed). Confirm signal changes smoothly and within expected range; if no change or out of range, suspect sensor or wiring.
  5. If sensor is analog but reference and ground are good and signal is invalid, measure sensor resistance across relevant pins (per OEM spec) to identify open/short.
  6. If communication-based sensor (module on network), use a scan tool to confirm the sensor module is present on the bus. Check CAN/LIN physical layer: measure CAN_H/CAN_L voltages and continuity to ECU, and verify proper termination resistance (~60 ohms across CAN_H to CAN_L with power off).
  7. Perform wiggle tests on harness and connectors while monitoring live data for intermittent faults. Repair any damaged wiring or connectors found.
  8. If wiring checks good and sensor fails bench or live tests, replace the wastegate position sensor and clear codes.
  9. If replacement does not restore communication, check for ECU or gateway module faults, update module software if service info indicates, and consider module replacement only after ruling out wiring and sensor faults.
  10. After repairs, clear codes and perform a road test or functional test to confirm the code does not return and turbo/wastegate behave normally.

Likely causes

  • Disconnected or corroded connector at the wastegate position sensor
  • Damaged sensor harness (open/short) between sensor and ECU
  • Failed wastegate position sensor
  • Loss of sensor reference voltage or ground
  • Communication bus fault (short to battery/ground or missing termination) preventing module messages

Fault status

⚠️ Status
Lost Communication With Wastegate Position Sensor A — the control module is not receiving a valid position signal or network message from the Wastegate Position Sensor A circuit.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours

Similar codes

U0100 U0121 U0155 U0021 U0415
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