Fuel and air

P0286 — Cylinder 9 Fuel Injector Circuit High

Severity: medium Drive with care, to a shop

What P0286 means

The engine control module (ECM) fires the cylinder 9 injector through a driver circuit and monitors the current and voltage in it. P0286 sets when those values are higher than expected, for example because of a shorted injector coil or a wire shorted to battery voltage. The injector may then fail to open correctly or stop working altogether.

Symptoms

  • Check engine light on with P0286 stored
  • Rough idle
  • Misfire or hesitation on cylinder 9
  • Reduced power and sluggish acceleration
  • Worse fuel economy
  • Engine vibration, especially under load

Possible causes

  1. Cylinder 9 injector with a shorted internal coil
  2. Damaged wiring harness or corroded, loose injector connector
  3. Injector wire shorted to battery voltage
  4. Faulty injector driver inside the ECM
  5. High system voltage from a failing alternator or voltage regulator

How to diagnose

  1. Scan all codes and freeze frame data and look for other injector or voltage codes
  2. Measure charging system voltage with the engine running and confirm it is in range
  3. Inspect the cylinder 9 injector harness and connector for chafing, melting and corrosion
  4. Measure the injector coil resistance and compare it with specs and neighboring injectors
  5. Check the injector wire for a short to power and to ground with the connector unplugged
  6. Check the injector control signal with a scope or noid light at the connector
  7. Review cylinder balance and fuel trims
  8. If wiring and injector test good, test the ECM and its driver

Common fixes

  • Repair damaged wiring and replace a bad connector
  • Replace the cylinder 9 fuel injector
  • Repair or replace the alternator or regulator if voltage is too high
  • Replace or repair the ECM if the injector driver is faulty

Questions and answers

What does P0286 mean?

It means the ECM detected abnormally high current or voltage in the cylinder 9 injector circuit. The cause is usually the injector, its wiring or the ECM driver.

Can I drive with code P0286?

Only briefly and to a repair shop. The misfire and dead cylinder can damage the catalytic converter, and the circuit fault can harm the ECM.

How do I tell a bad injector from a wiring problem?

Measure the injector coil resistance and test the wire for shorts. If the injector and wiring are good, the ECM is the next suspect.

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.