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P0204 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0204 is an OBD-II Code that refers to Injector Circuit Malfunction – Cylinder 4


A P0204 code is a generic diagnostic trouble code that occurs when the PCM/ECM detects a signal voltage input indicating poor performance on a fuel injector on Cylinder 4.

The solenoid-operated valve on each fuel injector allows pressurized fuel to flow out of the part. The valve is operated by a special transistor called a “driver” which then moves the valve to an open position. A dormant injector will read nearly equal to battery voltage, whereas an active one will pull its voltage down to near zero. If the injector’s voltage does not match the expected state voltage, the PCM generates the P0204 code.


Common causes for this code include:

  • Defective power supply wires to the fuel injectors
  • Connector or harness faults that cause bad or dead connections
  • Fuel injector may be clogged or full of dirt
  • Corroded fuel injector, hoses, or connections
  • For cylinder 2 injector circuit, either an open or a short wiring harness may be used.
  • The fourth cylinder has a faulty fuel injector


The symptoms of a P0204 code are:

  • Illuminated Check Engine Light 
  • Rough running
  • Stalling
  • Misfire
  • Poor fuel economy
  • Limp-in mode
  • Rich-running or lean-running
  • Hard-start condition


To diagnose a P0204 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the injector harness and connectors for damage, poor connections, or corroded pins.
  3. Check the fuel pressure and injector spray pattern.
  4. Check the ignition system for misfiring.
  5. Check the engine compression.
  6. Check for vacuum leaks.
  7. Remove the injector and check it for dirt or damage.
  8. Test the resistance of the injector driver.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P0204 code:

  • Not thoroughly inspecting all the wiring and connectors.
  • Not checking the fuel pressure or injector spray pattern.
  • Not checking the ignition system for misfiring.
  • Not checking the engine compression.
  • Not checking for vacuum leaks.
  • Replacing an injector without first verifying that it is defective.

How serious is this?

A P0204 code is considered to be a more serious code and should be addressed as soon as possible. Failing to address a P0204 code may result in poor engine performance and even engine damage.

What repairs can fix the code?

repair manuals

The following are solutions that may fix this problem:

  • Repair or replace any faulty parts such as wiring, connectors, or hoses.
  • Clean or replace the fuel injector if it is clogged or damaged.
  • Check the engine compression.
  • Test the resistance of the injector driver.
  • Replace the ECM/PCM if all other repairs have been exhausted.

Related codes

A P0204 is related to and may be accompanied by the following codes:

P0205 – Injector Circuit Malfunction – Cylinder 5

P0206 – Injector Circuit Malfunction – Cylinder 6

P0301 – Misfire Detected in Cylinder 1

P0302 – Misfire Detected in Cylinder 2


In conclusion, the P0204 code is a diagnostic trouble code that refers to a problem with the fuel injector on Cylinder 4. There are a number of potential causes for this code, and the most common ones should be checked first. The code usually results in poor engine performance and may cause damage if left untreated. Some possible repairs include repairing or replacing any faulty parts, cleaning or replacing the fuel injector, checking the engine compression, and testing the resistance of the injector driver.