Engine

P03A6 — Cylinder 2 Pressure Variation Low

Severity: medium Drive with care, to a shop

What P03A6 means

Engines with in-cylinder pressure sensors let the ECU monitor combustion quality in each cylinder. P03A6 means the cycle-to-cycle pressure variation in cylinder 2 is below the expected range. The cause may be a fuel, ignition or mechanical problem in that cylinder, or a bad sensor signal.

Symptoms

  • Check engine light on
  • Rough idle
  • Loss of power and sluggish acceleration
  • Misfire feeling or hesitation
  • Higher fuel consumption

Possible causes

  1. Faulty or clogged fuel injector on cylinder 2
  2. Worn spark plug or failing ignition coil on cylinder 2
  3. Low compression in cylinder 2 (valve, rings, gasket)
  4. Vacuum leak near cylinder 2
  5. Faulty cylinder pressure sensor or its wiring
  6. Damaged harness or poor connector contact

How to diagnose

  1. Scan all codes and freeze frame data, and look for misfire codes such as P0302.
  2. Inspect the wiring and connectors for the cylinder 2 sensor and coil.
  3. Check the spark plug and coil, and swap the coil with a neighbor to see if the fault follows.
  4. Test the cylinder 2 injector's resistance and listen for operation.
  5. Inspect the intake path and gaskets for vacuum leaks, using a smoke machine if possible.
  6. Run a compression or leak-down test on cylinder 2.
  7. If the mechanics are fine, scope the pressure sensor signal and compare it with other cylinders.

Common fixes

  • Replace the spark plug and/or ignition coil on cylinder 2
  • Clean or replace the cylinder 2 injector
  • Fix vacuum leaks and replace intake gaskets
  • Repair the sensor wiring or connector
  • Replace the faulty cylinder pressure sensor
  • Repair the engine if compression is low

Questions and answers

What does P03A6 mean?

The ECU detected that pressure in cylinder 2 varies too little from one cycle to the next. That points to poor combustion or a sensor fault.

Can I drive with P03A6?

Briefly and carefully, to a shop. If the check engine light flashes, stop, since misfires can damage the catalytic converter.

Where should I start diagnosing P03A6?

Start with the cylinder 2 spark plug and coil, then check the injector and vacuum leaks. If those are fine, test compression and the sensor.

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.