Fuel and air

P0273 — Cylinder 5 Injector Circuit Low

Severity: medium Drive with care, to a shop

What P0273 means

P0273 sets when the engine control module detects abnormally low voltage in the cylinder 5 injector control circuit. The module normally fires an injector by switching its circuit to ground and monitors the circuit voltage. A shorted wire, a failing injector coil or a faulty driver inside the module can pull the reading low and disrupt fuel delivery to that cylinder.

Symptoms

  • Check Engine light on
  • Rough or uneven idle
  • Misfire on cylinder 5
  • Hesitation or loss of power
  • Worse fuel economy
  • Engine vibration or hard starting
  • Higher exhaust emissions

Possible causes

  1. Failed cylinder 5 fuel injector (shorted or damaged coil)
  2. Open circuit or short to ground in the injector 5 wiring
  3. Corroded or loose injector connector
  4. Chafed or heat-damaged harness
  5. Faulty injector driver inside the PCM
  6. Problem with injector circuit power supply (fuse or relay)

How to diagnose

  1. Scan for codes and freeze frame data, and note any other injector or misfire codes
  2. Inspect the injector 5 connector and harness for corrosion, chafing and moisture
  3. Check the fuse and power supply to the injectors
  4. Measure injector coil resistance and compare it with the spec for your engine
  5. Swap the injector with a neighboring cylinder and see if the fault follows
  6. Test the wire to the PCM for opens and shorts to ground
  7. Check injector pulses with a noid light or a scope
  8. If the injector and wiring are good, test or replace the PCM

Common fixes

  • Replace the cylinder 5 fuel injector
  • Repair the wiring or replace the damaged harness section
  • Clean or replace the injector connector
  • Replace a blown fuse or faulty relay
  • Repair or replace the PCM if its injector driver has failed

Questions and answers

What does P0273 mean?

The PCM sees low voltage in the cylinder 5 injector circuit. The cause is usually the injector itself or wiring shorted to ground, and less often the PCM.

Can I drive with code P0273?

Only a short distance and gently. Misfires can damage the catalytic converter and cut power, and a flashing check engine light means you should stop.

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.