Fuel and air

P0204 — Cylinder 4 Fuel Injector Circuit Malfunction

Severity: medium Drive with care, to a shop

What P0204 means

The engine control module fires each injector by switching its circuit to ground through an output driver. P0204 sets when the module sees an open, short or out-of-range resistance in the cylinder 4 injector circuit. As a result, that cylinder may get the wrong amount of fuel or none at all.

Symptoms

  • Check Engine light on
  • Rough idle and engine shaking
  • Misfire or hesitation under throttle
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Often paired with misfire code P0304
  • Hard starting or a fuel smell from the exhaust

Possible causes

  1. Failed cylinder 4 fuel injector (open or shorted coil)
  2. Open or shorted wiring in the injector harness
  3. Corroded or loose injector connector
  4. Harness chafed against a hot or moving part
  5. Failed injector driver inside the PCM (less common)

How to diagnose

  1. Scan all codes and freeze-frame data, and note whether P0304 or other injector codes are present
  2. Inspect the cylinder 4 injector connector and harness for corrosion, damage or a poor fit
  3. Measure injector coil resistance and compare it to specification and to the other injectors
  4. Check for power and a control signal at the connector using a noid light or scope
  5. Test the control wire from the connector to the PCM for opens and shorts to ground or power
  6. Swap the cylinder 4 injector with a neighbor and see whether the code follows
  7. Review fuel trims and cylinder balance, and check fuel pressure
  8. If wiring and injector test good, evaluate the PCM and its driver

Common fixes

  • Replace the faulty injector
  • Repair the harness or replace the damaged connector
  • Clean the terminals and restore proper connector retention
  • Replace or reprogram the PCM if the driver is confirmed bad

P0204 on different brands

Ford · manuals
Ford documents the extended format P0204:92 for its 2024–2025 gasoline engines as a cylinder 4 injector circuit range/performance condition; it reports what the monitor detected, not a confirmed failed part.

Questions and answers

What does P0204 mean?

The engine computer found an electrical problem in the cylinder 4 injector circuit. The cause can be the injector, wiring, connector or, less often, the computer itself.

Can I drive with a P0204 code?

Only for a short distance until it is repaired. Running long with a dead cylinder can damage the catalytic converter and dilute the engine oil with fuel.

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

Measure the injector resistance and check the signal at the connector. You can also swap injectors between cylinders: if the code moves to the other cylinder, the injector is at fault.

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.