P0201
Cylinder 1 Injector A Circuit.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 01
- FaultThe specific fault in that area
What it means
P0201 means the engine control unit has detected a fault in the electrical circuit that drives the cylinder 1 fuel injector. The control unit monitors the injector driver and its wiring, and it sets the code when the current or voltage does not match what it expects, such as an open circuit, a short or a high resistance. The code points to the circuit rather than to a mechanical or fuel delivery fault, although the injector itself is a common cause.
Symptoms
- Engine management light on
- Misfire or rough running, especially at idle
- Hard starting or long cranking
- Loss of power and poor acceleration
- Increased fuel consumption
- Engine runs on fewer cylinders or stalls in some cases
Possible causes
- Faulty cylinder 1 injector with open or shorted coil windinglikely
- Damaged, chafed or corroded wiring between the injector and the control unitlikely
- Poor connection at the injector plug or control unit connector (corrosion, bent or loose pins)likely
- Wiring short to earth or to a supply voltage in the injector circuitpossible
- Faulty injector driver inside the engine control unitrare
- Blown fuse or relay fault affecting the injector supply (depends on model and engine layout)rare
How to diagnose
- Read all stored codes and freeze frame data, and note engine speed, load and temperature when the fault set. Check for other injector or misfire codes.
- Visually inspect the cylinder 1 injector connector and nearby wiring for damage, heat marks, oil contamination, chafing and corrosion.
- Disconnect the connector and check the terminals for tightness, green corrosion and bent or pushed-back pins. Make sure the locking clip is secure.
- Measure the injector coil resistance and compare it with the specification for that engine, as values vary by model and injector type.
- Check the supply voltage and the control signal at the injector connector against the wiring diagram, using a suitable test light or oscilloscope.
- Test the wiring for continuity, and for shorts to earth or to supply voltage, between the injector and the control unit connector with the battery disconnected.
- Swap the injector with another cylinder's, if the design allows, clear the code and see whether the fault follows the injector.
- If the injector and wiring are good, check the control unit connector and power and earth supplies, then consider the control unit only as a last resort.
How to fix
- Replace the faulty cylinder 1 injector and follow any coding or adaptation procedure the manufacturer specifies for that engine.
- Repair or replace damaged wiring and make sure the repair is properly insulated and protected from heat and rubbing.
- Clean or replace corroded or loose connector terminals, or renew the connector.
- Replace any blown fuse only after finding what caused it, and replace a faulty relay.
- Repair or replace the engine control unit if testing confirms a driver fault, and have it programmed to the vehicle.
Can I keep driving?
The car can usually be driven a short distance to a workshop, but avoid long journeys. A misfiring cylinder can overheat and damage the catalytic converter, and the engine may stall or lose power unexpectedly.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.