Parts
$15–80 per injector
P0204 — Injector Circuit Malfunction — Cylinder 4
STOPIs it safe to drive? Do not continue driving — a dead injector on any cylinder causes misfire damage to the catalytic converter rapidly; get it diagnosed promptly.
What P0204 means
Electrical fault in the cylinder 4 fuel injector circuit. May be an open, short, or resistance out of range. On 4-cylinder engines this is particularly impactful as it represents 25% of the power output.
Most likely causes (in order)
- Failed fuel injector (open or shorted)
- Loose or corroded injector connector — especially common on high-mileage 4-cylinder engines where the harness is well-worn
- Open in wiring harness to cylinder 4
- Heat damage to wiring near the exhaust manifold (cylinder 4 is often closest to the downpipe)
- PCM injector driver failure
Symptoms you might notice
- Misfire on cylinder 4 (P0304 companion code common)
- Strong vibration at idle on 4-cylinder engines
- Significant power loss
- Possible popping or backfire
- Fuel or rich smell from exhaust if injector stuck open
What to check first
Perform the swap test: swap the cylinder 4 injector connector with cylinder 3. If the code follows to P0203, the harness wiring is the fault. If it stays P0204, the injector is faulty. On 4-cylinder engines, also check for heat damage on the wiring near the number 4 exhaust port since that corner of the engine runs hottest.
Repair cost & difficulty
Labor
0.5–2.0 hr
Difficulty
Moderate