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?
- Yes, but fix soon
- 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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Common Symptoms
- Check Engine Light on
- Cylinder 4 misfire
- Rough idle
- Power loss
- Unburned fuel smell
Probable Causes (Ranked by Likelihood)
- 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
Step-by-Step Diagnostic Procedure
-
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.
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 Denso 23250-28080 if coil is faulty.
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.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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:
See All Codes & Fixes for Your Vehicle
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