What Does P0204 Mean?
This code indicates a malfunction in the fuel injector circuit for cylinder 4. The ECM has detected an electrical fault in the injector driver circuit that prevents proper fuel injection pulse delivery to cylinder 4. This results in a dead cylinder misfire and associated symptoms including rough idle, vibration, and increased emissions.
Common Causes
35%
Defective cylinder 4 fuel injector with internal coil open or short circuit
30%
Broken, corroded, or heat-damaged wiring at the cylinder 4 injector connector
20%
Faulty ECM injector driver for cylinder 4 output channel
15%
Injector power supply circuit fault from relay or fuse affecting injector operation
Diagnostic Steps
1
Step 1: Disconnect the cylinder 4 injector connector and measure coil resistance. Normal high-impedance injectors read 11-17 ohms. An OL or near-zero reading confirms injector failure.
2
Step 2: Check for 12V at the injector connector power pin with key on. If absent, trace the power feed through the relay and fuse.
3
Step 3: Use a noid light at the cylinder 4 connector during cranking to verify ECM pulse delivery. No pulse means the ECM driver or ground-side wire is faulty.
4
Step 4: Swap the cylinder 4 injector with an adjacent cylinder and clear codes. If the code moves to the swapped position, the injector is defective.
5
Step 5: Inspect harness routing near cylinder 4 for heat damage from the exhaust manifold or contact with sharp brackets. Repair any damaged insulation.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
This code indicates a malfunction in the fuel injector circuit for cylinder 4. The ECM has detected an electrical fault in the injector driver circuit that prevents proper fuel injection pulse delivery to cylinder 4. This results in a dead cylinder misfire and associated symptoms including rough idl...
The most common cause of P0204 (Injector Circuit Malfunction - Cylinder 4) is: Defective cylinder 4 fuel injector with internal coil open or short circuit
Typical repair costs for P0204 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A non-firing cylinder 4 injector causes persistent misfire, raw fuel in exhaust, and potential catalytic converter damage. Engine vibration and power loss affect drivability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0204 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Generic (SAE)
Recommended Tools
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