Injector Circuit Malfunction - Cylinder 4
The P0204 code means the vehicle's onboard diagnostic system has detected: Injector Circuit Malfunction - Cylinder 4. This is a serious severity code.
- Keep driving?
- Limited driving only
- DIY difficulty
- medium
- Estimated cost
- $25 - $1,200+ (a wiring or connector repair at the low end; injector replacement, or a PCM injector-driver/module repair with programming, at the high end)
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What Are the Symptoms of P0204?
- Check Engine Light on
- Cylinder 4 misfire
- Rough idle
- Power loss
- Unburned fuel smell
What Causes P0204? (Most Likely First)
- Open or shorted cylinder 4 injector circuit Very High
- Failed injector on cylinder 4 High
- Damaged harness connector at cylinder 4 High
- PCM injector driver fault for cylinder 4 Moderate
Can I Still Drive with P0204?
Limited driving only. P0204 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Common Fixes by Vehicle
What techs usually find when diagnosing P0204 on specific vehicles — tap your vehicle for the fix and the exact part:
2009-2020 Ford F-150/Explorer 5.0L Coyote Moderate DIY
Cylinder 4 injector circuit malfunction. Check the injector connector and measure coil resistance (11-15 ohms). On the Coyote V8, access to cylinder 4 injector requires removing the intake manifold on some configurations. If the injector tests good electrically, check for a shorted or open wire in the harness between the PCM and injector.
Labor: 1-2 hours2007-2017 Toyota Camry 2.5L Moderate DIY
Cylinder 4 injector circuit open or shorted. Check the connector for oil contamination and corrosion. Measure resistance (11-16 ohms). On the 2AR-FE, cylinder 4 is closest to the firewall and the harness routing makes it prone to chafing. Inspect the wiring for bare spots or shorts to ground. Replace with an OE-quality Denso unit if coil is faulty. Confirm the exact part for your year and engine with a retailer's fitment lookup or your VIN before ordering - these applications split by engine and build date.
Labor: 1-1.5 hours2010-2020 Hyundai Sonata/Kia Optima 2.4L Moderate DIY
Cylinder 4 injector circuit fault. Check the injector connector and wiring for damage. Measure resistance (13-16 ohms on Theta II). If resistance is out of spec, replace the injector. On high-mileage Theta II engines with oil consumption issues, carbon deposits on the injector tips can cause sticking. A professional fuel system cleaning may help.
Labor: 1 hourFrequently Asked Questions
Is it safe to run a 4-cylinder engine with one injector not firing?
No. Running on 3 cylinders sends unburned fuel into the exhaust, rapidly overheating and destroying the catalytic converter. A misfiring cylinder is also hard on the engine mechanically.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0204?
-
NOID light on cylinder 4 injector connector while cranking.
-
Injector resistance test.
-
Wiring continuity from injector to PCM.
-
Swap with a known-good injector from another cylinder and see if code follows.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
P0204 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Which Vehicles Commonly Get P0204?
- Honda Civic and Accord 4-cylinder
- Toyota Camry 4-cylinder
- Chevrolet Cobalt and Malibu
- Ford Focus and Fusion
- Mazda 3 and 6
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