Fuel and air

P0261 — Cylinder 1 Injector Circuit Low

Severity: medium Drive with care, to a shop

What P0261 means

The engine control module drives the cylinder 1 injector by switching its control circuit to ground and monitors the voltage in that circuit. P0261 is set when that voltage is lower than expected. Typical reasons are a wire shorted to ground, a failed injector coil, or a faulty driver inside the module.

Symptoms

  • Check Engine Light on
  • Rough idle or engine vibration
  • Misfire on cylinder 1
  • Hesitation or reduced power
  • Poor fuel economy
  • Hard starting in some cases

Possible causes

  1. Failed cylinder 1 fuel injector (shorted or open coil)
  2. Damaged, corroded or loose injector wiring and connector
  3. Injector control wire shorted to ground
  4. Poor power or ground supply to the injector circuit (fuse, relay)
  5. Faulty injector driver inside the PCM
  6. Moisture or oil contamination in the injector connector

How to diagnose

  1. Scan for codes and freeze frame data, and look for other injector or misfire codes.
  2. Inspect the cylinder 1 injector connector and harness for chafing, oil, corrosion and a poor latch.
  3. Measure injector coil resistance and compare it to the spec for your engine and to the other injectors.
  4. Check for power at the injector connector with the ignition on, and test the related fuse and relay.
  5. With the connectors unplugged, test the control wire for a short to ground and for continuity to the PCM.
  6. Use a noid light or scope to confirm the PCM sends injector pulses.
  7. If possible, swap the injector with a neighbor and see whether the fault follows it.
  8. Review fuel trims and cylinder balance, and check fuel pressure.

Common fixes

  • Replace the cylinder 1 fuel injector
  • Repair or replace the damaged wiring or connector
  • Restore power and ground to the injector circuit, replacing the fuse or relay if needed
  • Repair or replace the PCM if the injector driver is confirmed faulty

Questions and answers

What does P0261 mean?

The PCM sees too low a voltage in the cylinder 1 injector control circuit. The most common causes are a bad injector or a wire shorted to ground.

Can I drive with P0261?

Only briefly and carefully, to get to a shop. The engine will likely misfire, which can harm the catalytic converter and waste fuel.

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

Measure the injector resistance and check the control wire for a short to ground. If the injector is within spec but the wire is shorted, repair the harness. If the resistance is out of spec, replace the injector.

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.