Ignition

P03FC — Ignition K Control Circuit High

Severity: medium Drive with care, to a shop

What P03FC means

The engine control module monitors the circuit it uses to command one ignition channel, labeled K. P03FC sets when the signal in that circuit reads higher than expected, for example from an open circuit, a poor ground, or a failing coil or driver. Which cylinder channel K maps to depends on the manufacturer, so confirm the definition in service information for your vehicle.

Symptoms

  • Check engine light on or flashing
  • Rough idle
  • Misfires, shaking or stumbling
  • Hesitation when accelerating
  • Loss of power
  • Worse fuel economy

Possible causes

  1. Damaged wiring or a corroded connector at the coil or ignition module
  2. Poor ground in the ignition circuit
  3. Failed ignition coil or its built-in driver
  4. Faulty ignition module
  5. Worn spark plugs stressing the coil
  6. PCM fault (uncommon)

How to diagnose

  1. Scan all codes and freeze frame data, and look for misfire codes
  2. Look up which coil or cylinder channel K refers to on this vehicle
  3. Inspect the coil connector and harness for corrosion, chafing, oil or moisture
  4. Test power and ground at the coil connector with a multimeter
  5. Check the control signal from the PCM with a scope or tester
  6. Swap the coil with a neighbor and see whether the fault follows it
  7. Inspect spark plugs and gap
  8. Suspect the PCM only after everything else checks out

Common fixes

  • Repair the wiring or replace the connector
  • Restore the ground connection
  • Replace the ignition coil
  • Replace spark plugs
  • Replace the ignition module or PCM if confirmed faulty

Questions and answers

What does P03FC mean?

The PCM detected a high signal in the ignition K control circuit. Wiring, a coil or an ignition module is the usual cause. Verify the exact definition for your make and model.

Can I drive with P03FC?

Only briefly and with light loads. Misfires can damage the catalytic converter, and a flashing check engine light means you should stop the engine.

How do I fix P03FC myself?

Start by inspecting the coil connector and wiring, check the spark plugs, and swap the coil with another cylinder. If the fault stays, the signal and power need to be tested properly.

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.