P0203: Injector Circuit / Open - Cylinder 3
Quick Answer
Safe to drive (short-term)
P0203 tells you the engine computer found an electrical fault in the circuit of the cylinder 3 injector: open, shorted or outside its resistance limits. On a four-cylinder it is an inner cylinder next to cylinder 4, and on three-cylinder engines such as Ford's 1.0 EcoBoost it is the last cylinder in the row. Workshop wiring repairs cost about 65-220 EUR; a petrol injector fitted about 100-310 EUR.
- Severity
- Moderate · Fuel System
- Estimated repair cost
- From €5 to €650+, varies by vehicle
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Get Skanyx freeWhat does P0203 mean?
P0203 is a fuel system-related diagnostic trouble code classified as moderate severity.
What are the symptoms of P0203?
- Check engine light, which may flash under load
- Pronounced shaking at idle, felt strongly on three-cylinder engines
- Jerky response when accelerating gently
- Clear drop in pulling power
- Raw fuel smell from the exhaust
- Fuel economy worse than normal
What causes P0203?
Corroded or poorly latched connector on the cylinder 3 injector
: high
Damaged wire in the harness branch that runs to cylinder 3
: high
Internal open or short in the cylinder 3 injector coil
: medium
Problem in the feed shared by all the injectors, such as a fuse, relay or ground
: medium
Failed injector 3 driver in the engine control unit
: low
Is it safe to drive with P0203?
Generally yes, for short-term driving. Driving a short distance at low load is usually possible, but an injector fault on cylinder 3 costs you a cylinder, and on a three-cylinder engine that is a third of its power. A flashing check engine light means the catalytic converter is overheating, so stop and get the car recovered.
How do you diagnose P0203?
- Read P0203 and the freeze frame with Skanyx. Note any P0303 (cylinder 3 misfire), P0267 or P0268 (cylinder 3 injector circuit low or high) and other injector codes stored at the same time
- Work out where cylinder 3 is. On a four-cylinder engine it is the third from the pulley end, next to cylinder 4 at the gearbox end. On a three-cylinder engine it is the last cylinder, at the gearbox end. On V6 and V8 engines cylinder 3 is on bank 1 whichever numbering the maker uses
- Inspect the cylinder 3 injector connector and the branch of harness feeding it. Look for a cracked latch, corrosion in the pins and insulation worn through where the loom is clipped to the engine
- If P0203 was stored together with another injector code, check the shared supply fuse, relay and ground first. Two injectors failing at the same moment is much less likely than a fault in something they share
- Measure the injector coil at its pins with the ignition off, then repeat from the ECU pin for injector 3 to include the harness. Use the specification for your engine type
- Swap injector 3 with a neighbour, cylinder 2 or 4 (cylinder 2 on a three-cylinder), clear the code and drive. If the code moves with the injector, replace it; if P0203 stays, repair the wiring or check the ECU driver
- When a direct-injection injector is removed, fit new PTFE combustion seals before refitting. On common-rail diesels the injector correction codes must match each cylinder, which needs a brand tool or a workshop
How much does P0203 cost to fix?
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| DIY repair of the cylinder 3 connector or wiring | €5–€30 | €0–€0 | €5–€30 | Moderate |
| Cylinder 3 circuit traced and repaired at a workshop | €5–€40 | €60–€180 | €65–€220 | Professional |
| Cylinder 3 petrol injector replaced at a workshop | €40–€150 | €60–€160 | €100–€310 | Moderate |
| Cylinder 3 common-rail diesel injector replaced at a workshop | €150–€400 | €100–€250 | €250–€650 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Engines known for this code
P0203 on specific vehicles
P0203 on Volkswagen
Volkswagen Golf
P0203 on BMW
BMW 3 Series
P0203 on Ford
Ford Focus
P0203 on Mercedes-Benz
Mercedes C-Class
Related diagnostic codes
Common questions about P0203
- My engine has three cylinders. Is cylinder 3 the last one?
- Yes. On a three-cylinder engine such as Ford's 1.0 EcoBoost, cylinder 3 is the end cylinder, normally at the gearbox end. P0203 is therefore the highest injector circuit code that engine can set, and losing that cylinder costs about a third of the engine's output, so it runs very roughly.
- Which bank is cylinder 3 on?
- On V6 and V8 engines cylinder 3 ends up on bank 1 under both common numbering systems: makers that number one bank first put cylinders 1 to 3 or 1 to 4 on bank 1, and makers that alternate sides put the odd numbers there. A lean code with P0203 on a V engine is therefore expected on bank 1 (P0171).
- P0203 and P0204 appeared together. Are two injectors bad?
- Probably not. When two or more injector circuit codes appear at once, suspect something the circuits share first: the supply fuse or relay, a ground, a section of harness both branches run through, or the ECU. Test the shared parts before replacing injectors.
- Which injector should I swap with cylinder 3?
- Use a neighbour on the same rail, cylinder 2 or cylinder 4 on a four-cylinder and cylinder 2 on a three-cylinder. After the swap, clear the code and drive. A code that moves to the other cylinder number means the injector is faulty.
- Is P0203 safe to drive with?
- Only for a short, gentle trip. The engine loses a cylinder, pulls poorly and can overheat the catalytic converter. On a small three-cylinder engine the loss of power can also make joining fast traffic unsafe.
- What is the difference between P0203 and P0267 or P0268?
- All three concern the cylinder 3 injector circuit. P0203 is the general circuit or open-circuit code, while P0267 and P0268 say the control circuit is reading low or high. Which one your engine sets depends on how the manufacturer implemented the monitor.