P0204 Code – Injector Circuit Malfunction Cylinder 4

The P0204 diagnostic trouble code (DTC) indicates that the engine control unit (ECU) has detected a fault in the electrical circuit controlling the fuel injector for cylinder 4.

Fuel injectors are electronically controlled valves that deliver fuel into the combustion chamber. The ECU sends precise electrical pulses to each injector to regulate:

• injection timing

• fuel quantity

• combustion efficiency

When the ECU detects an abnormal condition in the injector circuit for cylinder 4—such as incorrect voltage, an open circuit, or a short circuit—it stores the P0204 code.

This code typically points to an electrical issue, not necessarily a failed injector.

Symptoms of Code P0204

Common symptoms include:

• Check Engine Light ON

• Engine misfire on cylinder 4

• Rough idle

• Engine vibration

• Poor acceleration

• Loss of power

• Increased fuel consumption

• Strong fuel smell from exhaust

In severe cases, the engine may stall or run unevenly.

Common Causes of P0204

Typical causes include:

• Faulty fuel injector (cylinder 4)

• Damaged or broken wiring

• Loose or corroded connector

• Open circuit in injector wiring

• Short circuit to ground or voltage

• Faulty ECU injector driver (rare)

• Blown fuse related to injector circuit

In many real-world cases, wiring or connector faults are more common than injector failure.

How Serious Is Code P0204

This is a high severity code.

If ignored, it may lead to:

• continuous engine misfires

• catalytic converter damage

• reduced engine performance

• long-term engine wear

If the Check Engine Light is flashing, the vehicle should not be driven.

How to Diagnose Code P0204

Recommended diagnostic steps:

1. Scan the vehicle with an OBD2 scanner

2. Confirm misfire on cylinder 4 (if present)

3. Inspect injector connector for corrosion or loose pins

4. Check wiring harness for continuity

5. Measure injector resistance and compare with specifications

6. Swap injector with another cylinder to test

7. Check ECU signal using a noid light or oscilloscope

How to Fix Code P0204

Possible repair solutions:

• replace the faulty injector

• repair or replace damaged wiring

• clean or secure electrical connectors

• replace blown fuse

• repair ECU (rare cases)

After repairs, clear the code and verify proper operation.

Difference Between P0200 and P0204

• P0200 indicates a general injector circuit malfunction

• P0204 indicates a specific issue with the injector on cylinder 4

Vehicles Commonly Affected

This code may appear on most vehicles equipped with electronic fuel injection, including:

• Opel / Vauxhall

• Volkswagen / Audi

• BMW

• Ford

• Mercedes-Benz

• Renault / Peugeot

• Toyota / Nissan / Hyundai

FAQ – P0204 Code

What cylinder is affected by P0204?

Cylinder 4.

Can I drive with P0204?

Short-distance driving may be possible, but it is not recommended due to risk of engine damage.

Does this code always mean a bad injector?

No. Electrical issues such as wiring faults or poor connections are very common.