What Does P0203 Mean?
This code indicates a malfunction in the fuel injector circuit for cylinder 3. The ECM has detected an open circuit, short to ground, short to voltage, or resistance out of specification in the cylinder 3 injector driver circuit. Cylinder 3 will not receive proper fuel pulses, leading to a misfire.
Common Causes
35%
Faulty cylinder 3 fuel injector with failed internal coil winding (open or shorted)
30%
Corroded or damaged wiring in the cylinder 3 injector circuit, often from heat exposure near the exhaust manifold
20%
ECM internal driver circuit failure for the cylinder 3 injector output
15%
Injector harness common power feed issue affecting cylinder 3 injector voltage supply
Diagnostic Steps
1
Step 1: Measure cylinder 3 injector coil resistance. Disconnect the connector and test across terminals with a DVOM. Expected resistance is 11-17 ohms for high-impedance type.
2
Step 2: Verify battery voltage (12V+) is present at the injector connector power terminal with key on. No voltage indicates a feed circuit fault.
3
Step 3: Connect a noid light to the cylinder 3 injector connector and crank the engine. A flashing noid light confirms ECM pulse; no flash indicates a wiring or driver issue.
4
Step 4: Swap the cylinder 3 injector with another cylinder to determine if the fault follows the injector or stays with the cylinder 3 wiring position.
5
Step 5: Trace the cylinder 3 injector control wire from the connector back to the ECM, checking for chafing, breaks, or shorts to ground along the harness route.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
This code indicates a malfunction in the fuel injector circuit for cylinder 3. The ECM has detected an open circuit, short to ground, short to voltage, or resistance out of specification in the cylinder 3 injector driver circuit. Cylinder 3 will not receive proper fuel pulses, leading to a misfire.
The most common cause of P0203 (Injector Circuit Malfunction - Cylinder 3) is: Faulty cylinder 3 fuel injector with failed internal coil winding (open or shorted)
Typical repair costs for P0203 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A dead cylinder from injector circuit failure causes unburned fuel to enter the exhaust, potentially overheating the catalytic converter. Reduced engine power may compromise vehicle performance during highway driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0203 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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