Fuel and air

P0270 — Cylinder 4 Injector Circuit Low

Severity: medium Drive with care, to a shop

What P0270 means

The engine control unit fires the cylinder 4 injector by switching its circuit to ground, and it monitors the voltage in that circuit. P0270 sets when the voltage is lower than expected, for example from a short to ground, a shorted injector coil or a failing driver in the control unit. The injector may then deliver the wrong amount of fuel or none at all.

Symptoms

  • Check engine light on
  • Rough idle or engine vibration
  • Loss of power or hesitation
  • Worse fuel economy
  • Cylinder 4 misfire, possibly with code P0304
  • Hard starting

Possible causes

  1. Corroded or damaged wiring and connectors in the injector circuit
  2. Faulty cylinder 4 injector (shorted coil)
  3. Injector wire shorted to ground, such as from chafed insulation
  4. Poor ground or power supply to the injector
  5. Damaged injector connector under the valve cover area
  6. Failed injector driver in the PCM (uncommon)

How to diagnose

  1. Scan all codes and freeze frame data and look for misfire codes such as P0304
  2. Inspect the cylinder 4 injector connector and harness for chafing, oil, corrosion or heat damage
  3. Measure injector coil resistance and compare to the engine's spec and to the other injectors
  4. Test the harness for a short to ground with the injector and PCM connectors unplugged
  5. Check for power and a good ground at the injector connector
  6. Swap the injector with a neighboring cylinder and see whether the fault follows
  7. Use a scope or noid light to confirm the PCM injector pulse
  8. Review fuel trims and cylinder balance, and check fuel pressure

Common fixes

  • Repair or replace damaged wiring and connectors
  • Replace the faulty fuel injector
  • Correct the power or ground supply problem
  • Repair or replace the PCM if the driver is confirmed faulty

Questions and answers

What does P0270 mean?

The PCM detected abnormally low voltage in the cylinder 4 injector control circuit. The cause is usually wiring, a connector or the injector itself.

Can I drive with P0270?

Only briefly and gently, for example to a shop. Extended driving with a dead cylinder can damage the catalytic converter and engine.

Should I replace the injector right away?

No. Check the wiring, connector and injector resistance first. Replace the injector only when tests or an injector swap point to it.

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.