01 Hybrid Automotive Cars and Insurance: What You Need to Know • 02 This Is Why The Air Recirculation Button Is So Important • 03 This Is Why Your Car’s CV Axle Is Failing • 04 Transmission Problems: Causes, Symptoms, and Solutions • 05 Honda Prologue: The Electric SUV That Will Lead Honda's EV … • 06 The Ultimate Guide to the Major Automotive Groups and Their… • 07 Understanding Your Mass Airflow Sensor: Function & Benefits… • 08 P0037 H02S heater control circuit low (Bank 1 sensor 2) • 09 Don’t Panic: Understanding Power Steering Fluid Leaks (Caus… • 10 B0037 and B0038: How to Fix AUX Switch Problems DTC Codes •

DTC codes / U06xx · Network communication / U0644

U0644Lost Communication With Wastegate Position Sensor A

U0644 is a network communication code indicating that a control module on the vehicle's controller area network (CAN) bus has lost contact with the wastegate position sensor A, which is typically a smart actuator with its own electronics. The module that monitors this sensor, often the engine control module (ECM) or a dedicated turbo control module, has stopped receiving valid position data over the communication network, so it cannot confirm the wastegate's actual position.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaNetwork communication

Symptoms you may notice

  • Illumination of the check engine light or a dedicated service warning for the turbo system.
  • Reduced engine power or a limp-home mode because the ECM cannot verify wastegate position and limits boost.
  • Poor acceleration and sluggish throttle response, especially at low engine speeds.
  • Rough running or hesitation under load if the wastegate remains stuck in one position.
  • Often no symptoms besides the warning light, particularly if the fault is intermittent and the actuator still moves correctly.
  • Possible increased fuel consumption or altered shift quality as the powertrain compensates for uncertain boost control.

Common causes, most likely first

  1. Damaged, corroded, or disconnected wiring and connectors in the wastegate position sensor circuit, including the CAN bus lines to the smart actuator.
  2. A failed wastegate position sensor or integrated actuator electronics that no longer communicates on the network.
  3. Low battery voltage or a weak charging system causing the actuator module to drop offline intermittently.
  4. Water intrusion or heat damage at the wastegate actuator connector, common on turbocharged engines exposed to road spray and high temperatures.
  5. A software or calibration fault in the ECM or turbo control module that disrupts communication with the actuator.
  6. A faulty CAN bus segment or a failed terminating resistor that affects only the module hosting the wastegate sensor.
  7. Physical damage to the wastegate linkage or actuator housing that prevents the sensor from reporting a plausible position.

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, then record freeze-frame data to see when and under what conditions U0644 set.
  2. Inspect the wastegate actuator connector and the full wiring harness for chafing, corrosion, water intrusion, and loose pins, repairing any damage found.
  3. Measure battery voltage and charging system output, and load-test the battery to rule out low-voltage communication dropouts.
  4. Check the CAN bus integrity at the actuator connector with a multimeter or oscilloscope, looking for correct differential voltage and no shorts to ground or power.
  5. Perform a bidirectional actuator test with a capable scan tool to command the wastegate through its range and confirm whether the sensor reports movement.
  6. If communication is restored but position readings are erratic, replace the wastegate position sensor or the complete smart actuator assembly as a unit.
  7. After repair, clear codes, perform any required adaptation or relearn procedure for the wastegate, and road-test to confirm the code does not return.

What Most Techs Miss on U0644

  • A smart wastegate actuator is a network node in its own right, so U0644 often appears when the actuator's internal electronics fail rather than when the sensor element itself is bad, and replacing only the sensor will not fix it.
  • Low battery voltage from a weak battery or a failing alternator can cause the actuator module to drop off the CAN bus intermittently, setting U0644 with no hard fault in the wiring.
  • Water intrusion at the actuator connector is a frequent hidden cause on turbocharged engines, and the corrosion often sits behind the connector seal where a quick visual check will not reveal it.
  • U0644 can be stored alongside boost control or turbo underboost codes, and technicians who chase the boost fault first may replace the turbo when the real problem is a communication fault at the actuator.
  • A failed or unplugged wastegate actuator can leave the wastegate in a default position that still allows limited boost, so the vehicle may feel almost normal and the code may be the only clue.

Can I keep driving with U0644?

You can usually drive the vehicle to a repair shop, but expect reduced power and avoid heavy acceleration or towing until the fault is repaired. If the engine enters limp mode or runs roughly, keep speeds low and schedule diagnosis promptly to prevent secondary turbo or engine damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage