Fuel Injector Circuit Malfunction Cylinder 4 (Ford)
What does P1204 mean?
The P1204 code means the vehicle's onboard diagnostic system has detected: Fuel Injector Circuit Malfunction Cylinder 4 (Ford). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Cylinder 4 misfire
- Rough idle
- Reduced engine power
- Increased exhaust emissions
Probable Causes (Ranked by Likelihood)
- Faulty cylinder 4 fuel injector Very High
- Open or short in cylinder 4 injector wiring High
- Corroded injector connector at cylinder 4 Moderate
- PCM injector driver circuit failure Moderate
- Damaged fuel injector harness Low
Step-by-Step Diagnostic Procedure
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Measure cylinder 4 injector coil resistance
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Inspect cylinder 4 injector connector for damage
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Test for injector pulse at cylinder 4 using a noid light
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Swap cylinder 4 injector with a known-good injector
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Check wiring from PCM to cylinder 4 for breaks or shorts
Frequently Asked Questions
Is cylinder 4 harder to access than other cylinders?
On inline 4-cylinder Ford engines, cylinder 4 is at the rear near the firewall and may be slightly harder to reach. On V6 and V8 engines, accessibility varies. Check your engine layout before starting the repair.
Can heat damage injector wiring?
Yes. Fuel injector wiring near exhaust components can suffer heat damage over time. The insulation can crack or melt, causing shorts or opens. Inspect wiring routing and add heat shielding if needed.
What happens if I ignore a bad fuel injector?
Running with a dead injector causes unburned fuel to enter the catalytic converter, which can destroy it. The lean misfire also causes excess heat in the cylinder, potentially damaging the piston and valves.