Engine

P03CE — Cylinder 6 Pressure Variation Low

Severity: medium Drive with care, to a shop

What P03CE means

The engine control unit tracks how pressure changes in cylinder 6 from one combustion event to the next, using a cylinder pressure sensor or inferred crankshaft data depending on the vehicle. P03CE sets when those changes are weaker than expected, which points to weak, incomplete or missing combustion in that cylinder. How the code is detected varies by manufacturer, so check the service information for your model.

Symptoms

  • Check Engine light on or flashing
  • Rough idle or vibration
  • Loss of power and sluggish acceleration
  • Worse fuel economy
  • Hesitation or stumbling under throttle
  • Possible misfire codes such as P0306

Possible causes

  1. Worn spark plug or failing ignition coil on cylinder 6
  2. Clogged or leaking fuel injector on cylinder 6
  3. Low compression in cylinder 6: worn rings, burnt or leaking valve, head gasket damage
  4. Vacuum leak or uneven intake airflow near cylinder 6
  5. Faulty cylinder pressure sensor, or crankshaft/camshaft sensor problem
  6. Damaged wiring or poor connector contact at the coil, injector or sensor

How to diagnose

  1. Scan all codes and freeze-frame data; look for related misfire codes (P0306) or sensor faults
  2. Inspect the cylinder 6 spark plug and coil for wear, cracks, oil or arcing
  3. Swap the coil (or plug) with a neighboring cylinder and see whether the fault follows
  4. Check connectors and wiring for the coil, injector and cylinder pressure sensor for corrosion, breaks or shorts
  5. Test the injector's resistance and operation, and run an injector balance test if possible
  6. Inspect the intake for vacuum leaks and review fuel trims
  7. Run a compression or leak-down test on cylinder 6
  8. If the mechanical side is fine, check crank, cam and pressure sensor signals with a scope

Common fixes

  • Replace the spark plug and/or ignition coil on cylinder 6
  • Clean or replace the cylinder 6 fuel injector
  • Fix vacuum leaks and replace damaged hoses or gaskets
  • Repair wiring and connectors, or replace a faulty sensor
  • Repair the engine internals (valves, rings, cylinder head) if low compression is confirmed

Questions and answers

What does P03CE mean?

The ECU sees less pressure variation in cylinder 6 than expected. This usually means combustion there is weak or incomplete. The cause can be ignition, fuel delivery or an engine mechanical problem.

Can I drive with P03CE?

Only briefly and gently, to reach a shop. Misfires can damage the catalytic converter. If the check engine light flashes, do not drive the car.

Where should I start diagnosing P03CE?

Start with the cylinder 6 spark plug and coil, the most common and cheapest cause. Swap the coil with another cylinder and see if the fault moves. If it doesn't, 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.