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U0644 — Lost Communication Wastegate Position Sensor

Generic OBD-II · all makesNetwork / communication

Code U0644 indicates that the engine control module (ECM) has lost communication with the wastegate position sensor. This typically means the computer is not receiving the expected data signal from the sensor used to monitor turbocharger boost pressure regulation.

Symptoms

What causes it — most likely first

1. Wiring Damage

Wires leading to the sensor are often exposed to extreme heat from the turbocharger, leading to melted insulation or brittle conductors.

2. Failed Wastegate Position Sensor

Internal electrical failure of the sensor prevents it from transmitting data to the control module.

3. Corroded or Loose Connectors

Moisture or debris in the sensor connector can cause high resistance or a complete break in the communication circuit.

4. Blown Fuse

A blown fuse in the engine management circuit may deprive the sensor of necessary power.

5. Control Module Failure

The engine control module (ECM) may have an internal fault preventing it from processing the sensor signal.

How it's diagnosed

  1. Scan the vehicle for all active DTCs and review freeze frame data to identify when the loss of communication occurred.
  2. Visually inspect the wiring harness surrounding the turbocharger for signs of heat damage, fraying, or abrasions.
  3. Unplug the wastegate position sensor connector and check for corrosion, bent pins, or moisture.
  4. Perform a continuity test on the signal and power wires between the sensor and the ECM.
  5. Measure the voltage supply at the sensor connector to ensure it is receiving the correct operating voltage.
  6. Use an oscilloscope or advanced scan tool to verify if the sensor is sending a signal during wastegate movement.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0640 — Lost Communication Evap Fuel Vapor TemU0641 — Lost Communication Evap System PressurU0642 — Lost Communication Evap System PressurU0643 — Lost Communication TurbochargersuperchU0645 — Lost Communication Active Air Dam ModuU0646 — Lost Communication Motor Electronics C

Frequently asked

Can I ignore this code if the car feels normal?

No. Loss of wastegate monitoring can lead to overboost conditions, which may cause permanent internal engine damage.

Should I replace the ECM if I see a communication code?

No. Communication codes are most frequently caused by wiring or sensor failure; replacing the ECM without first verifying the wiring is usually unnecessary and incorrect.

Does this mean my turbocharger is physically broken?

Not necessarily. This is an electrical communication code; the turbocharger may be mechanically sound, but the computer cannot verify the wastegate's position.