Engine

P03AE — Cylinder 3 Pressure Too Low

Severity: medium Drive with care, to a shop

What P03AE means

The engine control unit detected that pressure in cylinder 3 during combustion is lower than expected. It judges this from an in-cylinder pressure sensor, if fitted, or from uneven crankshaft speed. It usually means the mixture is burning poorly or the cylinder is leaking compression because of a spark, fuel, air or mechanical problem.

Symptoms

  • Rough idle and vibration
  • Loss of power and sluggish acceleration
  • Check engine light on or flashing
  • Hesitation or jerking under load
  • Higher fuel consumption
  • Raw fuel smell from the exhaust

Possible causes

  1. Worn or faulty spark plug in cylinder 3
  2. Failed ignition coil on cylinder 3
  3. Faulty or clogged fuel injector on cylinder 3
  4. Vacuum or intake leak near cylinder 3
  5. Low mechanical compression: valves, rings or head gasket
  6. Faulty cylinder pressure sensor or its wiring, where fitted

How to diagnose

  1. Scan all codes and freeze frame data and look for related misfire codes such as P0303.
  2. Inspect the wiring and connectors for the cylinder 3 coil, injector and pressure sensor.
  3. Remove the cylinder 3 spark plug and check its condition.
  4. Swap the coil (and plug) with a neighboring cylinder and see whether the fault follows.
  5. Test the injector: coil resistance, operation by sound, balance or flow.
  6. Check the intake for leaks, for example with a smoke machine.
  7. Run a compression or leak-down test on cylinder 3.
  8. Test the in-cylinder pressure sensor and its signal, if the engine has one.

Common fixes

  • Replace the cylinder 3 spark plug (ideally the full set)
  • Replace the cylinder 3 ignition coil
  • Clean or replace the cylinder 3 fuel injector
  • Fix intake leaks and replace damaged hoses or gaskets
  • Repair the engine: valves, rings or head gasket
  • Repair the wiring or replace the cylinder pressure sensor

Questions and answers

What does P03AE mean?

The engine computer found too little pressure in cylinder 3. Most often combustion is weak because of the spark plug, coil or injector; less often the cylinder is losing compression.

Can I drive with P03AE?

Only a short distance at light load to get to a shop. If the check engine light flashes, shut the engine off to avoid damaging the catalytic converter.

Where should I start diagnosing P03AE?

Check the spark plug and coil on cylinder 3 by swapping them with another cylinder. If the problem stays in cylinder 3, move on to the injector and a compression test.

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.