P0203
Injector Circuit Malfunction - Cylinder 3
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Code P0203 means the engine control module has detected an electrical problem in the fuel injector circuit for cylinder 3. This code specifically identifies that cylinder 3's injector is not responding as expected when the ECM commands it to open and deliver fuel. The issue is electrical in nature — either the injector itself, the wiring, the connector, or the ECM's output driver.
When cylinder 3's injector isn't working properly, you'll experience engine misfires, rough idling, and a noticeable reduction in power. The engine may hesitate when you press the accelerator, and you'll likely see increased fuel consumption as the ECM tries to compensate. On some vehicles, you may also notice the tachometer fluctuating slightly at idle due to the uneven power delivery.
The most efficient way to diagnose this is the injector swap test: move cylinder 3's injector to another cylinder position. If the code changes to match the new position, the injector is bad and should be replaced. If the code stays on cylinder 3, inspect the wiring harness and connector carefully. Look for wires that may have rubbed through their insulation against engine components, and check connector pins for green corrosion or signs of heat damage.
Severity
Symptoms
- •Check Engine light is on
- •Engine misfires and runs unevenly
- •Decreased engine power
- •Poor fuel economy
- •Vibration from engine at idle
- •Hesitation during acceleration
Likely Causes
Cylinder 3's fuel injector has developed an internal electrical fault — either an open circuit in the coil or a short — preventing it from operating.
The wire harness to cylinder 3's injector is damaged from heat, vibration, or contact with sharp edges, resulting in an open or short circuit.
The electrical connector at the injector has corroded pins or a loose fit, causing intermittent or total loss of the injector signal.
The engine control module's internal output driver for cylinder 3's injector has failed, even though the wiring and injector may be fine.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the cylinder 3 fuel injector
- Repair damaged wiring or connectors to cylinder 3 injector
- Clean corroded injector connector terminals
- Perform injector swap test to isolate the problem
Shop Parts
Videos
Causes and Fixes P0203 Code: Injector Circuit/Open Cylinder 3
HVAC Mechanic
P0203 Code - Meaning, Causes. How to fix?
OBD Insights
FIX P0200 P0201 P0202 P0203 P0204 P0205 P0206 P0207 P0208 P0209 FUEL INJECTOR CIRCUIT MALFUNCTION
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