P0479 code meaning
Exhaust Pressure Control Valve A Intermittent
Powertrain system Generic code P04xx codes Check engine light
What P0479 means
The exhaust pressure control valve is a flap in the exhaust: on older Navistar/Ford diesels a warm-up flap that raises back pressure when cold, on Ram and others an exhaust brake, on VW's 2.0 TDI a flap that drives the low-pressure EGR, and on Audi and Bentley a sound flap. P0479 means an intermittent circuit or function fault of valve A. No manufacturer document available to us uses this code; Audi describes its flap faults as mostly sporadic under P0475/P0477, and Bentley distinguishes intermittent from static faults in the fault memory. Typical causes are a loose contact or commutator wear in the flap motor. CARB requires output components to be monitored.
P0479 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0479
- Check engine light on, possibly only after several events
- Occasional flap noise or malfunction
Common causes of P0479
- Most likelyLoose contact in connector or wire
- PossibleFlap motor with commutator wear
- PossibleMoisture in the connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Exhaust pressure control valve aValve actuatorActuator wiringEngine control module
What each part of P0479 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 79 | The exact fault in that area. |
What to do next
- Note P0479 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0479
What does P0479 mean?
P0479 means "Exhaust Pressure Control Valve A Intermittent". The exhaust pressure control valve is a flap in the exhaust: on older Navistar/Ford diesels a warm-up flap that raises back pressure when cold, on Ram and others an exhaust brake, on VW's 2.0 TDI a flap that drives the low-pressure EGR, and on Audi and Bentley a sound flap. It is a generic code, so it means the same on every make.
Is it safe to drive with P0479?
Drive gently and only to a workshop. With P0479 the car can go into limp mode (reduced power) to protect itself.
Will P0479 fail an emissions test?
Yes, it can. P0479 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0479 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P0479 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.