Fuel and air

P02E9 — Diesel Intake Air Flow Position Sensor Circuit High

Severity: medium Drive with care, to a shop

What P02E9 means

The engine control unit monitors the position of the diesel intake air flow valve through a position sensor signal. That signal should stay within a normal range. P02E9 sets when the signal voltage is higher than expected. The usual causes are a wiring fault such as an open or short to power, or a failed sensor.

Symptoms

  • Check engine light on
  • Low or rough idle
  • Reduced power and sluggish response
  • EGR system operation disrupted
  • DPF regeneration problems

Possible causes

  1. Failed intake air flow position sensor (often built into the throttle body assembly)
  2. Signal wire shorted to power
  3. Open circuit in the signal or ground wire
  4. Corroded or loose connector terminals
  5. ECU internal fault or software issue (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and note any intake, EGR or DPF codes
  2. Inspect the harness and sensor connector for chafing, moisture, corrosion and a loose fit
  3. Clear the code and see whether it returns immediately or under certain conditions
  4. Watch the valve position reading on a scan tool while commanding it open and closed
  5. Measure the 5 V reference and ground at the sensor connector
  6. Test the signal wire for a short to power or an open back to the ECU
  7. If the wiring is good, test or replace the sensor (throttle body assembly)
  8. Suspect the ECU only after everything else checks out: test or reprogram it

Common fixes

  • Repair the wiring harness and connectors
  • Replace the position sensor or the complete throttle body assembly
  • Clean the connector terminals and restore a secure fit
  • Repair or reprogram the ECU if the wiring and sensor are good

Questions and answers

Can I drive with code P02E9?

Usually for short distances, though power may be reduced. Get it diagnosed soon to avoid EGR and DPF regeneration problems.

What most often causes P02E9?

Most often a wiring or connector fault, such as a short to power or an open circuit. The next most likely cause is the sensor itself, which is often part of the throttle body.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.