Ignition

P03FB — Ignition K Control Signal Circuit Low

Severity: medium Drive with care, to a shop

What P03FB means

The engine control module detected that the voltage in the control circuit for ignition coil K is lower than expected. The module normally uses this circuit to command the spark for a specific cylinder, and the signal level must match what it commands. The letter K is just one of the ignition control channels; which cylinder it maps to depends on the engine, so check the manufacturer's information.

Symptoms

  • Check engine light on
  • Misfire or rough running
  • Shaking at idle
  • Poor acceleration and reduced power
  • Worse fuel economy
  • Hard starting

Possible causes

  1. Failed ignition coil or ignition module
  2. Open, short to ground or corrosion in the ignition control wiring
  3. Loose, damaged or corroded coil connector
  4. Faulty ignition driver inside the control module
  5. Worn or incorrect spark plugs

How to diagnose

  1. Scan all codes and freeze frame data, and look for misfire codes (P030x)
  2. Use the wiring diagram to find which coil or cylinder channel K controls
  3. Inspect the connector and harness for chafing, moisture, corrosion or a loose fit
  4. Test the coil's power and ground supply with a multimeter
  5. Check the control signal from the module with a scope or noid-style test light
  6. Swap the coil with a neighboring one and see whether the code or misfire follows
  7. Inspect the spark plugs and replace them if worn
  8. Test the control wire back to the module for opens and shorts to ground

Common fixes

  • Repair damaged wiring or replace the connector
  • Replace the faulty ignition coil or module
  • Replace the spark plugs as a set
  • Repair or replace the control module if the signal is missing while wiring is good

Questions and answers

What does P03FB mean?

It means the ignition K control signal circuit is reading low. The module sees a lower than expected voltage on the coil control line, usually from a coil, wiring or module problem.

Can I drive with P03FB?

Only briefly and gently if the engine runs smoothly. If it misfires, avoid driving because unburned fuel can damage the catalytic converter.

What should I check first?

Start with the connector and wiring at the affected coil, then the coil and spark plugs. Suspect the control module last, after the wiring and coil test good.

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.