P0204 is a generic OBD-II powertrain fault code that means Injector Circuit/Open Cylinder 4. The ECM/PCM has detected an electrical problem in the fuel injector circuit for Cylinder 4.
P0204 may be encountered on applicable vehicles from Toyota, Duramax-powered Chevrolet/GMC vehicles, Volkswagen, Jeep, and Hyundai. The exact injector design, wiring arrangement, cylinder numbering, and diagnostic procedure vary by engine and model year.
Fault Code Description
P0204 = Injector Circuit/Open Cylinder 4.
Code type: Generic OBD-II Powertrain Code.
Likely fault location: Cylinder 4 fuel injector, injector connector, injector wiring, injector power supply, injector control circuit, or, less commonly, the ECM/PCM injector driver.
The word Open indicates that the ECM/PCM has detected an interruption or abnormal electrical condition in the Cylinder 4 injector circuit. It does not automatically mean that the injector itself has failed.
What Does P0204 Mean?
The ECM/PCM controls the Cylinder 4 fuel injector through an electrical circuit and monitors its electrical response. If the expected circuit condition is not detected, P0204 may be stored.
An open wire, excessive resistance, poor connector contact, loss of injector power, an internal injector fault, or a problem with the injector control circuit can cause this code.
Symptoms of P0204
- Check Engine Light.
- Engine misfire.
- Rough or unstable idle.
- Hesitation during acceleration.
- Loss of engine power.
- Poor fuel economy.
- Hard starting.
- Engine vibration.
- Engine may stall in severe cases.
- Flashing Check Engine Light when a severe misfire occurs.
Common Causes of P0204
- Faulty Cylinder 4 fuel injector.
- Open injector circuit.
- Broken injector control wire.
- Damaged injector connector.
- Loose or corroded electrical terminals.
- High resistance in the injector circuit.
- Loss of injector power supply.
- Damaged wiring near the engine.
- Intermittent connection caused by heat or vibration.
- Incorrect previous wiring repair.
- ECM/PCM injector driver fault.
How to Fix P0204
1. Scan the Vehicle
Confirm P0204 with a professional scan tool and check for additional injector, misfire, fuel-system, or electrical codes. Related codes can help determine whether the problem is isolated to Cylinder 4.
2. Identify Cylinder 4
Confirm the location of Cylinder 4 using the vehicle-specific service information. Cylinder numbering can differ between engine configurations.
3. Inspect the Injector Connector
Inspect the Cylinder 4 injector connector for loose terminals, corrosion, contamination, damaged locking tabs, or poor electrical contact.
4. Check Injector Power and Control
Use the correct vehicle wiring diagram to identify the injector power and control circuits. Verify the expected voltage and control signal according to the manufacturer's specifications.
5. Test Injector Resistance
Where permitted by the manufacturer, measure the resistance of the Cylinder 4 injector and compare it with the specification for the exact engine and injector type.
Do not apply a generic resistance specification to every vehicle because gasoline and diesel injector designs can differ substantially.
6. Check Injector Wiring
Inspect the complete circuit between the injector and ECM/PCM. Look for broken wires, damaged insulation, high resistance, short circuits, and wiring affected by heat, vibration, or previous repairs.
7. Verify the ECM/PCM Driver
If the injector, connector, power supply, and wiring are verified to be correct, test the ECM/PCM injector driver according to the manufacturer's diagnostic procedure before considering module replacement.
P0204 Diagnostic Signal Flow
↓
Cylinder 4 Injector Control Circuit
↓
Injector Connector
↓
Cylinder 4 Fuel Injector
↓
Fuel Delivery
↓
Cylinder 4 Combustion
P0204 OBD Live Data
Use OBD live data to monitor engine RPM, misfire counters, fuel trims, and other available cylinder or injector-related parameters. Compare Cylinder 4 with the other cylinders when cylinder-specific data is available.
Live data should be combined with direct electrical testing because P0204 is primarily an injector circuit fault. An intermittent wiring or connector problem may not remain visible throughout a scan.
P0204 Toyota, Duramax, Volkswagen, Jeep and Hyundai
P0204 has the same generic OBD-II definition on applicable Toyota, Duramax-powered Chevrolet/GMC, Volkswagen, Jeep, and Hyundai vehicles, but the actual injector circuit, injector technology, wiring layout, and diagnostic procedure can differ significantly.
P0204 Toyota
On applicable Toyota vehicles, inspect the Cylinder 4 injector connector, wiring, power supply, and control circuit. Confirm Cylinder 4 identification for the specific engine before testing.
Use Toyota-specific injector resistance and circuit specifications rather than a generic value.
P0204 Duramax
On applicable Duramax diesel engines, P0204 requires attention to the Cylinder 4 injector electrical circuit and the engine-specific injector control system.
Because Duramax injection systems use different electrical and fuel-pressure strategies than typical gasoline systems, follow the exact engine-specific diagnostic procedure before condemning the injector.
P0204 Volkswagen
On applicable Volkswagen vehicles, check the Cylinder 4 injector, connector, wiring, power supply, and control circuit. The exact testing method depends on the engine and injection system.
Use the vehicle-specific wiring diagram and injector specifications when performing electrical tests.
P0204 Jeep
On applicable Jeep vehicles, inspect the Cylinder 4 injector circuit for damaged wiring, poor connector contact, abnormal resistance, or an injector control problem.
Heat and engine vibration can contribute to intermittent injector-circuit faults.
P0204 Hyundai
On applicable Hyundai vehicles, check the Cylinder 4 injector connector, wiring, power supply, and control circuit. Compare cylinder-specific data where available.
Confirm the exact engine configuration before applying injector resistance or voltage specifications.
The basic P0204 definition remains the same, but the injector technology and circuit design can be very different between Toyota, Duramax, Volkswagen, Jeep, and Hyundai. Manufacturer-specific service information should always be used for final testing.
Is P0204 Serious?
P0204 can be serious if Cylinder 4 is not receiving the correct fuel delivery and the engine is misfiring. Severe misfires can cause poor drivability, increased emissions, and possible catalytic-converter damage on applicable gasoline engines. On diesel applications, continued operation with an injector fault can also affect engine performance and combustion.
Can I Drive With P0204?
Limited driving may be possible if the engine is running normally, but the fault should be diagnosed promptly. If the Check Engine Light is flashing, the engine is severely misfiring, or there is significant loss of power, continued driving should be avoided.
P0204 Repair Cost
- Electrical diagnosis: approximately $50–$150+.
- Injector wiring repair: approximately $50–$250+.
- Fuel injector replacement: approximately $100–$600+ depending on the vehicle and injector type.
- Diesel injector replacement: can cost considerably more depending on the Duramax or other diesel application.
- ECM/PCM diagnosis or repair: can cost considerably more.
These are general estimates only. Actual repair costs depend on the vehicle, engine, injector type, parts prices, labor rate, and whether the application is gasoline or diesel.
Common Repair Mistakes
- Replacing the injector without testing the circuit.
- Ignoring the injector connector.
- Failing to verify injector power and control.
- Using a generic injector resistance specification.
- Ignoring wiring damage near the engine.
- Using the wrong cylinder numbering.
- Replacing the ECM/PCM before testing the injector circuit.
- Ignoring related misfire or injector codes.
Related Codes
- P0200 – Injector Circuit Malfunction.
- P0201 – Injector Circuit/Open Cylinder 1.
- P0202 – Injector Circuit/Open Cylinder 2.
- P0203 – Injector Circuit/Open Cylinder 3.
- P0304 – Cylinder 4 Misfire Detected.
FAQ About P0204
What does P0204 mean?
P0204 means Injector Circuit/Open Cylinder 4. The ECM/PCM has detected an abnormal electrical condition in the fuel injector circuit for Cylinder 4.
How do I fix P0204?
Confirm Cylinder 4, inspect the injector connector and wiring, test injector power and control, measure injector resistance where applicable, and verify the ECM/PCM control circuit before replacing components.
Can a bad injector cause P0204?
Yes. A defective Cylinder 4 injector can trigger P0204, but the injector should not be replaced until its electrical circuit, connector, and power supply have been tested.
Can wiring cause P0204?
Yes. An open wire, high resistance, damaged insulation, short circuit, or poor connector contact can interrupt Cylinder 4 injector operation and trigger P0204.
Can P0204 cause a misfire?
Yes. If Cylinder 4 does not receive the correct injector command or fuel delivery, the cylinder can misfire and cause rough running, hesitation, vibration, and loss of power.
Does P0204 mean the ECM is bad?
No. An ECM/PCM fault is possible but should generally be considered only after the injector, connector, power supply, wiring, and control circuit have been tested.
Is P0204 the same on Toyota, Duramax, Volkswagen, Jeep and Hyundai?
The base definition is generic, but the injector technology, wiring layout, cylinder numbering, electrical specifications, and diagnostic procedure can differ between Toyota, Duramax, Volkswagen, Jeep, Hyundai, and different engine families.
Final Takeaway
P0204 should be approached as a Cylinder 4 injector circuit fault, not automatically as a failed fuel injector. The most reliable diagnosis is to test the injector, connector, power supply, wiring, control signal, and ECM/PCM driver in the correct sequence.
For applicable Toyota, Duramax, Volkswagen, Jeep, and Hyundai vehicles, identify the exact engine and Cylinder 4 location before testing. Vehicle-specific wiring diagrams and manufacturer specifications should be used to determine the actual source of the fault.