P03AF code meaning
Cylinder 3 Pressure Too High
Powertrain system Generic code P03xx codes Check engine light
What P03AF means
Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. This code concerns cylinder 3. P03AF means the pressure measured or calculated for the cylinder is higher than expected. It is documented by code at Audi, surprisingly on a gasoline engine: on the 2015 S3 (2.0 TFSI, engine CYFB) the four 'pressure too high' codes came on with the EPC lamp, usually together with misfire codes P0300–P0304 and the manufacturer code for hiding a cylinder; the cause was a software fault that mis-detected misfire, and a software update fixed it. How Audi determines the pressure, the bulletin does not say. On diesels with pressure-sensing glow plugs GM patents describe a peak pressure above its limit – too much or too early injection, or a sensor drifting upwards. If the cylinder is shut off, power drops noticeably.
P03AF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P03AF
- EPC or check engine light on
- Misfire codes, possibly a cylinder shut off with noticeable loss of power
- Rough running
Common causes of P03AF
- Most likelyEngine module software (Audi S3 2015, engine CYFB)
- PossibleInjector delivering too much or dripping
- PossibleSensor drifting upwards (diesel pressure-sensing glow plug)
- Less likelyKnock or pre-ignition on a gasoline engine
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder pressure sensor glow plugSensor wiringEngine control moduleFuel injector
What each part of P03AF means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3 | Area: ignition system or misfire. |
| AF | The exact fault in that area. |
What to do next
- Note P03AF 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 P03AF
What does P03AF mean?
P03AF means "Cylinder 3 Pressure Too High". Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. It is a generic code, so it means the same on every make.
Is it safe to drive with P03AF?
Drive gently and only to a workshop. With P03AF the car can go into limp mode (reduced power) to protect itself.
Will P03AF fail an emissions test?
Yes, it can. P03AF 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 P03AF to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P03AF 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.