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P0204 OBD-II Trouble Code: Injector Circuit Malfunction - Cylinder 4

Check Engine Light

P0204 code definition

Injector Circuit Malfunction - Cylinder 4

What the P0204 code means

  • The Engine Control Module (ECM) runs checks on all systems at startup, and many times a second while the vehicle is running. P0204 tells technicians a malfunction was found for cylinder 4 injector circuit.

  • This code is similar to P0200 - P0203, and P0205 - P02012.

  • Lean and rich condition codes along with misfire codes may be found with P0204 as well.

What causes the P0204 code?

  • ECM is faulty
  • Open or shorted wiring harness
  • Failing cylinder 4 injector
  • Poor electrical connection

What are the symptoms of the P0204 code?

Symptoms may be felt before the ECM triggers the Check Engine Light. Some symptoms of P0204 include:

  • Poor fuel economy
  • Rich & lean conditions
  • Engine misfires
  • Lack of engine power
  • Poorly running engine
  • Engine that dies and will not restart

When these symptoms are detected, the Check Engine Light is triggered and the ECM puts the vehicle into a failsafe mode to protect the car from damage. Once a failsafe mode is set, it will remain until the code is cleared, the fault is fixed, or a normal range is achieved.

With the severity of some of these symptoms, caution is advised.

How does a mechanic diagnose the P0204 code?

  1. Hooks up a scan tool into the diagnostic link connector (DLC) port on the car and pulls all codes that are stored in the system

  2. Observes the freeze frame data associated with the codes (each one tells the technician when the code was triggered and what the vehicle was doing)

  3. Clears all the codes and performs a test drive under similar conditions obtained from the freeze frame data

  4. Performs a visual inspection if the P0204 code returns

  5. Uses the scan tool to check for proper ECM readings coming from the injector circuit cylinder 3

  6. Checks the voltage with a multimeter at cylinder 3 fuel injector

  7. If needed, installs a noid light between the fuel injector and its wiring (noid lights measure the voltage pulse width which tells technicians if the injector is opening for long enough)

  8. Performs a test of the ECM if none of the other tests offer anything conclusive

Common mistakes when diagnosing the P0204 code

Generally a competent mechanic will not make mistakes when diagnosing P0204 as long as they follow all steps and do not skip anything. The cylinder 4 fuel injector is the most common cause of P0204, especially on higher mileage vehicles, but that does not mean it does not need to be tested.

How serious is the P0204 code?

On a scale of 1 to 5, P0204 is a 3 on the seriousness scale. P0204 can cause mild symptoms like poor gas mileage and the Check Engine Light being present, but it can also cause serious issues that will cause the engine to run poorly, be difficult to keep running, or die without being able to restart it.

What repairs can fix the P0204 code?

Additional comments for consideration regarding the P0204 code

On higher mileage vehicles with over 100k miles, it is not uncommon for dirt and contaminants found in gasoline to cause fuel components to fail. Injectors can become clogged by particles and fail to operate. In some cases, a fuel system cleaner, such as Seafoam, can be used to clean varnish and contaminants from the fuel system. This may be a cheaper alternative to try before replacing the fuel injector.

Specialized tools may be necessary to diagnose P0204 effectively and properly. One such tool is a noid light set. These are installed between the fuel injectors and the wiring harness to test for the voltage pulse width of the fuel injector. Voltage may be checked at the fuel injector and it may pass fine, then a noid light is installed only to find the pulse width is not correct for the fuel injector.

Scan tools that allow technicians to view live data and the changes that occur over time are needed to diagnose codes such as P0204 on modern cars. They will show live information that can be graphed to track down difficult issues.

Need help with a P0204 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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