P0203: Injector Circuit / Open - Cylinder 3

P0203 means the engine control unit detected an electrical fault (open circuit, short, or out-of-range resistance) in the wiring or driver for the cylinder 3 fuel injector. The injector itself may be fine while the wiring, connector, or ECU driver is at fault. Left unrepaired it causes a cylinder 3 misfire. Typical repair runs about 60 to 350 EUR depending on whether it is wiring or a replacement injector.

P0203 is a fuel system-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0203 and illuminates the check engine light.

If your vehicle has triggered P0203, you may notice one or more of these symptoms:

• Check engine light illuminated, often flashing under load
• Rough idle and noticeable misfire
• Hesitation or stumble on acceleration
• Loss of power and reduced fuel economy
• Raw fuel or sulphur smell from the exhaust
• Hard starting when cold

Here are the most common causes of P0203, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Drivable short-term, but a dead or intermittent cylinder 3 injector causes a misfire that dumps unburnt fuel into the exhaust and can overheat and destroy the catalytic converter. Expect rough running and reduced power. Repair promptly to avoid a much more expensive catalyst replacement.

Follow these steps to pinpoint the root cause of P0203:

1. Read the stored code and freeze frame with Skanyx to confirm it is P0203 and note the conditions (RPM, load, coolant temp) when it set
2. Check for companion misfire codes (P0300 or P0303) which point to a genuine combustion problem on cylinder 3
3. Inspect the cylinder 3 injector connector and harness for corrosion, looseness, melted pins, or chafing
4. With the engine off, measure the injector winding resistance with a multimeter and compare against the workshop spec (most petrol injectors read roughly 12-17 ohms)
5. Check for the injector control and supply circuits with a multimeter or test light, and swap the suspect injector to another cylinder to see if the fault follows it
6. Note that per-injector coding, flow balance, and quantity-correction values are not on generic OBD2 - read those with a brand tool such as Carly, OBDeleven, or XENTRY, or have a workshop verify them

Repair costs for P0203 vary depending on the root cause and your vehicle. Here are typical estimates:

P0203 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0203 or indicate related issues: