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DTC codes / U06xx · Network communication / U0674

U0674Lost Communication With Wastegate Position Sensor B

U0674 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 B circuit, typically the sensor or its local module. The computer detected that expected messages from that sensor or its associated module stopped arriving within the required time window, or that the module reported an internal fault with the sensor signal.

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

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message, often with no other symptoms besides the warning light
  • Reduced engine power or limp mode due to the turbocharger wastegate being held at a default position
  • Poor acceleration or sluggish throttle response because boost pressure cannot be regulated normally
  • Rough running or hesitation under load if the wastegate remains partially open or closed
  • In rare cases, a no-start condition if the lost communication affects a module shared with the engine immobilizer or powertrain control

Common causes, most likely first

  1. Failed wastegate position sensor B or its internal circuitry
  2. Damaged, corroded, or disconnected wiring and connectors between the sensor and its control module
  3. Faulty control module that the sensor communicates through, such as the engine control module or a dedicated turbo control module
  4. Open or shorted CAN bus data lines (CAN High or CAN Low) affecting the module that hosts the sensor signal
  5. Low battery voltage or poor grounds causing intermittent communication dropouts
  6. Aftermarket electronic accessories improperly tapped into the CAN bus, causing signal interference
  7. Software or calibration issue in a module that requires a reflash or update

How to diagnose and fix it

  1. Perform a full scan of all modules to confirm U0674 is active and check for related communication codes that narrow the fault to a specific bus segment
  2. Inspect the wastegate position sensor B connector and wiring for corrosion, chafing, or loose pins, and repair as needed
  3. Measure reference voltage and ground at the sensor connector with the key on to verify the sensor is receiving power and ground
  4. Check the CAN bus data lines for proper resistance (about 60 ohms across the bus) and for shorts to ground or battery voltage
  5. Substitute a known-good wastegate position sensor B or perform a bidirectional test if the scan tool supports it, then clear codes and retest
  6. If the sensor and wiring test good, check for technical service bulletins or software updates for the control module that handles the sensor signal
  7. As a last step, diagnose or replace the control module only after confirming all power, ground, and bus communication paths are intact

When the sensor is not the culprit

  • A loose or corroded ground connection at the turbocharger or engine block can cause the wastegate position sensor signal to drop out intermittently, setting U0674 without any sensor fault.
  • The code can be set by a low battery or charging system issue that causes modules to reboot during cranking, so always check battery health and voltage drop before replacing parts.
  • Aftermarket piggyback tuners or improper wiring for accessories on the CAN bus often introduce communication errors that mimic a failed wastegate sensor.
  • U0674 does not always mean the sensor itself has failed; the communication loss can originate in the module that interprets the sensor signal, so module power and ground must be verified.
  • On some vehicles, the wastegate position sensor B is part of an assembly that includes the turbocharger actuator, and a mechanical binding in the wastegate linkage can cause the sensor to report implausible values that lead to a communication fault.

Can I keep driving with U0674?

You can usually drive the vehicle with U0674, but expect reduced engine power and poor acceleration because the turbocharger wastegate may default to a safe position. Avoid heavy throttle or towing until the fault is repaired, and have the vehicle diagnosed promptly to prevent secondary damage to the turbocharger or catalytic converter.

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.

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