Short, gentle driving is usually possible, but a persistent misfire from this can damage the catalyst — don't defer the repair, and stop if it stalls or the light flashes. P0204 is an electrical fault in the fuel-injector circuit for cylinder 4 — an open, short, or out-of-range reading on the wiring that drives that injector. It is not the same as a clogged injector; the injector can be physically fine but electrically disconnected. Very often the cause is a chafed wire or a corroded connector rather than the injector itself, so check the wiring before buying parts.
What P0204 means
The engine computer fires each injector by driving its control wire, and it monitors that circuit for a healthy electrical load. When the current or voltage on cylinder 4's injector circuit is wrong — an open, a short, or resistance outside the expected window — it sets P0204. This is a circuit fault, separate from the injector's spray performance.
Symptoms
- Check-engine light on
- Misfire, stumble or rough idle traceable to cylinder 4
- Hesitation or lack of power on acceleration
- Hard starting, or in severe cases a no-start or stall
- Higher fuel use and a possible raw-fuel smell
- Sometimes intermittent — comes and goes with a chafed wire or loose connector
Common causes
- A faulty cylinder 4 injector with an open or shorted internal winding (common at higher mileage)
- Damaged, chafed or broken wiring in the injector circuit
- A corroded, loose or backed-out connector pin at the injector
- A poor or lost power supply to the injector
- An open or shorted control (driver) circuit from the computer
- Corrosion or water intrusion in the harness or connector
- Less common: a failed injector-driver output inside the computer
Severity & driving advice
Severity: Moderate — Cylinder 4 may be misfiring or getting no fuel, running the engine rough and, if it dumps fuel, threatening the catalytic converter.
Can I drive? Short, gentle driving is usually possible, but a persistent misfire from this can damage the catalyst — don't defer the repair, and stop if it stalls or the light flashes.
Diagnostic approach
- Confirm the code and check for companion codes — Scan for other injector-circuit codes (P0201–P0208) and freeze-frame; several together point to a shared feed, ground or computer issue rather than one injector.
- Inspect the connector and harness — Unplug cylinder 4's injector and check for corrosion, pushed-out terminals and chafed or melted wiring near hot or moving parts — many of these codes are wiring, not the injector.
- Measure injector resistance — Measure the injector winding and compare to spec and to the other injectors; an open or shorted reading condemns the injector.
- Verify power and control signal — With the connector off, confirm feed voltage is present and use a test light or scope to verify the computer is pulsing the control circuit while cranking; no pulse points upstream to wiring or the driver.
- Check power and ground integrity — Check continuity from the injector connector back to the computer and to the power feed, looking for opens or high resistance.
- Swap to isolate — If unsure, swap the suspect injector with a known-good one; if the circuit code follows the injector, replace it; if it stays on cylinder 4, the fault is wiring or the driver.
- Repair, clear and retest — Fix the wiring or connector, or replace the injector, clear the code, and drive to confirm P0204 does not return.
FAQ
Does P0204 mean my injector is clogged?
Not necessarily. This is an electrical-circuit fault (open, short or wiring), which is different from a clogged injector; the injector can be physically fine but electrically disconnected.
Can a wire cause this instead of the injector?
Yes, very often. A chafed harness, corroded pin or poor ground triggers the same code, so inspect the connector and wiring before buying an injector.
Is it safe to keep driving?
Briefly and gently, but an ongoing misfire risks catalytic-converter damage, so treat it as a soon-to-fix item.
Why did a misfire code show up too?
If cylinder 4 loses fuel it misfires, so the injector-circuit code and a cylinder-4 misfire code often appear together and usually share the same root cause.