Fuel Injector Circuit Malfunction Cylinder 3 (Ford)
What does P1203 mean?
The P1203 code means the vehicle's onboard diagnostic system has detected: Fuel Injector Circuit Malfunction Cylinder 3 (Ford). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Cylinder 3 misfire
- Engine vibration at idle
- Reduced power
- Rough running and poor fuel economy
Probable Causes (Ranked by Likelihood)
- Failed cylinder 3 fuel injector Very High
- Wiring fault in cylinder 3 injector circuit High
- Corroded injector connector Moderate
- PCM driver issue for cylinder 3 Moderate
- Injector wiring harness chafing Low
Step-by-Step Diagnostic Procedure
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Test cylinder 3 injector resistance with a multimeter
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Check the injector connector for corrosion and secure fit
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Verify injector pulse with a noid light at cylinder 3
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Swap cylinder 3 injector with another cylinder to isolate the fault
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Inspect the wiring harness along the fuel rail for damage
Frequently Asked Questions
Where is cylinder 3 on a Ford engine?
On Ford inline 4-cylinder engines, cylinder 3 is the third from the front. On Ford V6 engines, cylinder 3 is typically the rear cylinder on the passenger side. On V8 engines, it is the second cylinder from the front on Bank 1.
Can multiple injector codes appear at once?
Yes. If the injector harness has damage affecting multiple wires, or if the PCM has a driver circuit issue, multiple cylinder injector codes can set. Check the common harness and PCM connections first.
What is a noid light and where can I get one?
A noid light is an inexpensive tool that plugs into the injector connector and flashes when the PCM sends an injector pulse. They are available at auto parts stores for $10 to $20 and are essential for injector circuit diagnosis.