Fuel and air

P00AF — Turbo/Supercharger Boost Control "A" Module Performance

Severity: medium Drive with care, to a shop

What P00AF means

The engine computer compares commanded boost pressure with actual pressure and monitors the module or actuator that controls the turbo or supercharger. P00AF sets when boost control module "A" doesn't perform as commanded, for example it responds too slowly, doesn't reach its target position, or boost doesn't match the request. What "module A" refers to varies by manufacturer and turbo design.

Symptoms

  • Check engine light on
  • Reduced power and sluggish acceleration
  • Erratic boost and surging under throttle
  • Limp mode
  • Poor throttle response
  • Unusual turbo noise or whistling

Possible causes

  1. Faulty boost control solenoid or actuator
  2. Open, shorted or corroded wiring and connectors
  3. Boost or vacuum leaks (cracked hoses, loose clamps)
  4. Faulty boost pressure sensor
  5. Sticking variable geometry mechanism or bad actuator position sensor
  6. PCM fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and note any other boost-related codes
  2. Inspect charge-air pipes, intercooler, clamps and vacuum lines for cracks, oil and leaks
  3. Compare commanded and actual boost in live data during acceleration
  4. Check actuator or vacuum capsule movement through its full range for binding
  5. Inspect wiring and connectors to the solenoid, actuator and sensors for power, ground and corrosion
  6. Check the boost pressure sensor reading with the engine off
  7. Test the solenoid resistance and control signal
  8. Consider a PCM software update only after ruling out mechanical causes

Common fixes

  • Replace the boost control solenoid or actuator
  • Repair wiring and connectors
  • Fix leaks: replace hoses, clamps and vacuum lines
  • Replace the boost pressure sensor
  • Clean or replace the turbo if the geometry is stuck
  • Reprogram or replace the PCM only after confirming it is at fault

Questions and answers

What does P00AF mean?

The PCM detected that boost control module "A" isn't performing as required, so boost pressure doesn't match the target. The cause can be electrical, mechanical or an air leak.

Can I drive with P00AF?

Only briefly and gently to get to a shop. Power will be down, and prolonged driving risks damaging the turbo or engine.

What should I check first?

Look for boost leaks in hoses and pipes, check the wiring and connectors of the solenoid or actuator, then compare commanded and actual boost on a scan tool.

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.