OBD-II trouble code
P0204: Injector Circuit/Open - Cylinder 4
The engine computer detected an electrical fault in the fuel injector control circuit for cylinder 4 — usually the wiring, connector, or injector coil. Cylinder 4 may lose fuel and misfire, so diagnose it promptly.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $50 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0204 mean?
The engine control module (ECM) fires each fuel injector by pulsing its control circuit — battery voltage feeds one side of the injector while the ECM switches the ground on the other side for a precise number of milliseconds. It watches the electrical feedback, and when the voltage or current doesn't match the command it sets an injector-circuit code. P0204 isolates that fault to the cylinder 4 injector circuit.
Because the code already points at one cylinder, the diagnosis is targeted. On a four-cylinder engine, cylinder 4 is usually at the opposite end of the block from cylinder 1, but numbering is defined by the manufacturer, so confirm the layout for your engine before testing — especially on a V6 or V8 where cylinder 4 may sit on either bank.
"Circuit/Open" describes an electrical problem, and the wiring is the more common cause: a broken or chafed wire, a corroded or backed-out connector pin, a poor ground, or a blown fuse. The cylinder 4 injector coil can also fail open. An injector that never gets pulsed leaves cylinder 4 without fuel, so P0204 commonly appears with a cylinder 4 misfire (P0304), rough running, and reduced power.
Common causes
- Broken, chafed, or shorted wiring to the cylinder 4 injector
- Corroded, loose, or backed-out connector pins at the cylinder 4 injector
- Open or shorted coil winding inside the cylinder 4 injector
- Poor ground or a bad shared power feed affecting the injector
- Blown injector fuse (can affect cylinder 4 alone or a group)
- Rarely, a failed cylinder 4 injector driver inside the ECM/PCM
Symptoms
- Check engine light on, sometimes flashing if cylinder 4 is dead
- Rough idle and engine shaking
- Loss of power and hesitation on acceleration
- A cylinder 4 misfire (often a companion P0304)
- Raw-fuel smell or increased fuel consumption
- Hard starting in some cases
Diagnostic steps
- 1.Confirm the code is P0204 and note any companion codes, especially a cylinder 4 misfire (P0304).
- 2.Identify the cylinder 4 injector for your engine, then inspect its connector and wiring for corrosion, chafing, or backed-out pins; wiggle-test while watching live data.
- 3.Measure the cylinder 4 injector's coil resistance with the key off and compare it to specification and to the other injectors. An open or out-of-spec reading condemns the injector.
- 4.Use a noid light or scan-tool injector test at the cylinder 4 connector to confirm the ECM is pulsing the circuit.
- 5.Check the injector's power feed and ground, and swap-test with a known-good injector if resistance is borderline.
- 6.If the wiring, fuse, ground, and injector all test good but the drive pulse is missing, suspect the injector driver in the ECM/PCM.
Repair cost
$50 – $1,500
A wiring or connector repair is often $50-$200. A single fuel injector runs $60-$400 in parts plus 0.5 to 3 hours of labor depending on how accessible cylinder 4 is — a top-of-intake port injector is quick, while direct-injection or lower-intake injectors take longer. A failed ECM injector driver is rare and runs $500-$1,500 with programming.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with fuel injector replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.