P0204 - Injector Circuit Malfunction (Cylinder 4)
P0204 means the injector circuit for cylinder 4 is malfunctioning. The injector may have failed, but damaged wiring, poor connector terminal fit, an open or short in the control circuit, or a PCM driver issue in rarer cases can set the same code.
Code first. Confirm symptoms and checks before pricing parts.
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Common Next Steps
Turn the code into the next check.
Check coil boots, carbon tracking, and whether the miss follows a swap.
Inspect gap, fouling, wear, oil, coolant, and plug-well condition.
Move to injector balance, pulse, or leak-down checks if the misfire stays.
Use compression or leak-down testing when spark and fuel checks do not move the fault.
Code Overview
P0204 means the injector circuit for cylinder 4 is malfunctioning. The injector may have failed, but damaged wiring, poor connector terminal fit, an open or short in the control circuit, or a PCM driver issue in rarer cases can set the same code.
Common Causes
- Injector failure
- Wiring issue
- Connector pin fitment
- ECM driver issue (rare)
Symptoms
- Rough idle or cylinder 4 misfire
- Hesitation or reduced power
- Fuel smell or poor fuel economy in some cases
Diagnostic Steps
- Inspect cylinder 4 injector connector fit and terminal condition
- Check for harness damage, rub-through, or corrosion near the injector
- Verify injector resistance if appropriate for the application
- Verify injector power and control pulse with proper test equipment
- Confirm cylinder 4 spark and compression before condemning fuel control alone
Diagnostic Insight
P0204 should be diagnosed as a cylinder 4 injector circuit fault before the injector itself is condemned.
- A circuit code can come from the connector, harness, power feed, or control side, not just the injector.
- If cylinder 4 also misfires, confirm spark and compression so fuel control is not blamed for a different fault.
- Resistance, pulse, and terminal-fit checks usually come before injector replacement.
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Next Steps
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