2018 Ford F-150 2.7L Twin Turbo: Diagnosing P0035 and P0471 Codes

Diagnosing P0035: Turbocharger Bypass Valve Circuit

• 💡 The initial code P0035 indicates a turbocharger bypass valve control circuit high, often pointing to an open circuit.
• 🔍 After consulting service data, the bypass valve (TCBY) was identified as a two-wire solenoid located at the left front edge of the engine compartment.
• ⚡ A fuse check confirmed power, but further testing revealed no power at the component, suggesting an open circuit or broken wire.
• 🛠️ A visual inspection uncovered a broken gray wire near the connector, likely caused by previous repair work, which was then repaired with a crimp seal.

Diagnosing P0471: Exhaust Pressure Sensor Range Performance

• 🎯 The second code, P0471, signifies an exhaust pressure sensor range performance error.
• 🔍 Initial data stream analysis showed a skewed exhaust pressure reading of 16.8 PSI, significantly higher than the expected barometric pressure of around 14 PSI.
• ⚠️ It was determined that the vehicle has two distinct exhaust pressure sensors: a DPFE (differential pressure feedback EGR) sensor and a separate exhaust pressure sensor.
• 🧩 The problematic sensor was identified as a two-wire unit, likely a temperature sensor, while the three-wire unit was for pressure. Upon unplugging the three-wire sensor, readings became erratic, confirming it as the faulty component.

Sensor Testing and Replacement

• 🔬 Testing revealed the exhaust pressure sensor had a 5V reference and a ground, but the signal wire showed a voltage drop when probed, indicating a potential issue.
• ✅ A quick circuit integrity test by grounding the signal wire confirmed the computer's ability to pull the signal to ground, suggesting the sensor itself was skewed.
• 🚗 The faulty exhaust pressure sensor was replaced with a new one, and post-replacement data showed the exhaust pressure reading normalized to 14.3 PSI, aligning with barometric pressure.

Conclusion and Next Steps

• 🏁 With both the broken wire and the skewed sensor addressed, DTCs were cleared, and the vehicle was ready for further testing.
• 💡 The technician noted that many issues encountered are related to failed physical layers like connectors and harnesses, rather than just component failures.
• 🔧 The video concludes with the successful repair of the F-150, highlighting a standard diagnostic process for these types of codes.