Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.
P0201: Cylinder 1 injector circuit malfunction
The ECU has detected an abnormal electrical condition in the injector circuit assigned to cylinder 1.
What P0201 means
The ECU has detected an abnormal electrical condition in the injector circuit assigned to cylinder 1. This identifies a circuit, not automatically a failed injector. Cylinder 1’s physical position must be confirmed from reliable vehicle information rather than guessed.
Can I still drive?
Treat it as needing prompt attention. If the warning is steady and the engine remains completely smooth, only a short, low-load journey to a garage may be reasonable. Stop and arrange recovery for a flashing warning, strong judder or misfire, stalling, substantial power loss, fuel smell or leakage, or heavy smoke. Continued severe misfire can cause secondary damage.
Symptoms
- Engine-management light, often with P0301.
- Rough idle, vibration or a noticeable misfire.
- Hesitation and reduced acceleration.
- Hard starting or stalling, although an intermittent circuit fault may cause no constant symptom.
Common causes
- Failed or out-of-specification cylinder 1 injector coil.
- Open, shorted, chafed or heat-damaged cylinder 1 wiring.
- Loose or corroded connector, poor terminal tension or a backed-out pin.
- Injector supply fuse, relay or power-feed problem, particularly if other injector codes are present.
- ECU driver fault, which should be proved only after external circuit checks.
Safe first checks
- Save the code status and freeze-frame data and note P0301 or any other injector, supply-voltage or communication codes. With the ignition off and engine cool, inspect the cylinder 1 connector and accessible loom for a loose plug, damaged lock, corrosion, oil, water or rubbed insulation. Confirm cylinder numbering from manufacturer-quality data. Use only the specified fuse rating. Leave resistance, voltage, pulse and oscilloscope tests to someone with the correct wiring diagram and specifications; do not open high-pressure fuel lines or disconnect a direct injector while the engine runs.
Typical UK fix cost
Approximately £50–£100 for diagnosis, £100–£300 all-in for a straightforward connector, fuse or local wire repair, or roughly £150–£900 for one injector depending on fuel system, access, removal difficulty and coding. Extensive loom or confirmed ECU-driver work needs a separate quote and may exceed that range.
Related models
This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.
Related fault codes
- P0193: Fuel rail pressure sensor “A” circuit high
- P0200: Injector circuit malfunction
- P0202: Cylinder 2 injector circuit malfunction
- P0203: Injector circuit fault, cylinder 3
Sources
- Pico Technology: injector voltage and current testing
- OBD-Codes: P0201 technical overview
- Bosch Aftermarket: DTC and electrical-circuit diagnosis
A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.