U02AF: Lost Communication With Turbocharger Turbine Inlet Valve Position Sensor

What it means

The vehicle bus reports loss of communication with the turbocharger turbine inlet valve position sensor. Position feedback for variable inlet geometry on twin-scroll/sequential turbo systems is missing.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The turbocharger turbine inlet valve position sensor reports the position of a valve used to manage variable inlet geometry on certain twin-scroll or sequential turbo systems. The engine controller monitors the sensor's network messages; U02AF sets when those messages are lost, leaving inlet-valve position feedback unavailable.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules for communication and turbocharger faults, then review freeze-frame data for conditions when the inlet valve sensor stopped reporting.
2. Check live data for turbine inlet valve position sensor communication and any available position reading.
3. Inspect the sensor connector and accessible bus wiring around the turbocharger for loose connections, heat damage, chafing, or corrosion.
4. Check the sensor or its module's power and ground circuits using the manufacturer's procedure.
5. Test the network wiring to the turbine inlet valve position sensor for an open, short, or poor connection.
6. If its power, ground, and network wiring pass, follow the manufacturer's checks to confirm sensor or module failure.

Common fixes

• Reconnect or clean the turbine inlet valve sensor connector.
• Repair heat-damaged or chafed communication wiring.
• Restore the sensor or module's power or ground supply.
• Replace the turbine inlet valve position sensor or its module if testing confirms failure.

Can I keep driving?

The engine may limit turbo output and acceleration, so avoid hard acceleration and overtaking where you need full power. If the engine runs poorly or displays additional warnings, stop safely and arrange service.