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Home / DTC / U066B — Lost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor

U066B — Lost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor

Detailed page for trouble code U066B.

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U066B

Generic U — Network/User

Lost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor

Brand: Generic
Type: U — Network/User
Views: UK: 19 EN: 24 RU: 18
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Page language: EN

Causes

  • Open/short in sensor wiring (power, ground, signal, or communication line)
  • Corroded, loose, or damaged connector at the sensor or harness
  • Failed bypass valve position sensor (internal electronics or potentiometer/Hall element)
  • Faulty bypass valve actuator or mechanical binding preventing correct sensor feedback
  • Loss of reference voltage or ground from the control module
  • CAN/LIN bus or module communication fault

Symptoms

  • Malfunction Indicator Lamp (MIL) or check engine light illuminated
  • Reduced engine power or limp-home mode
  • Erratic or low turbo boost, poor acceleration
  • Unusual turbo noise or wobbling boost response
  • Stored related boost control or actuator codes

What to check

  • Read all stored DTCs and freeze-frame data with a scan tool; note any other network or boost-related codes
  • Visually inspect the bypass valve, sensor connector, and wiring for damage, corrosion, or contamination
  • Wiggle harness and connectors while monitoring live data to reproduce the fault
  • Check for proper reference voltage (usually ~5V) and ground at the sensor connector
  • Command the bypass valve with a bidirectional scan tool and observe sensor feedback
  • Check CAN/LIN bus integrity if sensor communicates over a network: bus voltage, continuity, and other modules present

Signal parameters

  • Typical analog position signal: approx. 0.5–4.5 V across valve travel (varies by design)
  • Reference voltage: ~5 V (sensor powered from ECU reference) — verify specific vehicle data
  • Ground: chassis/ECU ground continuity required
  • On networked sensors (LIN/CAN): expect correct bus idle voltages and valid packet traffic when commanded
  • Sensor resistance (if applicable): compare to OEM spec with connector disconnected

Diagnostic algorithm

  1. Connect a factory-level or capable OBD-II scanner. Record U066B and any related codes and freeze frame data.
  2. Inspect the bypass valve B area, connector, and harness for physical damage, corrosion, or contamination. Repair any obvious issues.
  3. With ignition ON (engine off), backprobe the sensor connector. Verify presence of reference voltage, ground, and signal line resting voltage per vehicle specifications.
  4. Command the bypass valve (if supported) using the scan tool and observe that the sensor signal changes smoothly. If no change, try manually actuating the valve (if safe) and watch feedback.
  5. If reference or ground is missing, trace continuity back to the ECU and repair open/shorts. Repair corroded/loose connector pins as required.
  6. If reference and ground are present but no valid signal, measure sensor resistance (if applicable) or substitute a known-good sensor to confirm a sensor fault.
  7. If sensor is networked and no communication is present, check CAN/LIN bus voltage, continuity, termination resistors, and other modules on the bus. Repair bus faults.
  8. Repair or replace wiring, connector, sensor, or actuator as indicated. After repairs, clear codes and conduct a road test or boost-actuation test to confirm the issue is resolved.
  9. If fault persists after component/harness replacement, consider ECU/module diagnostics or reflashing per manufacturer procedures.

Likely causes

  • Damaged connector or wiring at the bypass valve sensor (most common)
  • Failed position sensor on the bypass valve
  • Intermittent or missing 5V reference or ground to the sensor
  • Network communication fault (bus wiring, termination, or another module driving the bus)

Fault status

⚠️ Status
Lost communication with turbocharger/supercharger bypass valve B position sensor. Control module not receiving expected position feedback — may affect boost control and engine performance.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0164 U0415 U0073
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