Injector Circuit/Open Cylinder 1
The P0201 code indicates that the Powertrain Control Module (PCM) has detected a malfunction, specifically an open circuit or abnormal voltage/resistance, in the fuel injector circuit for cylinder 1. The engine computer sets this code when it commands the cylinder 1 injector to operate but does not observe the expected electrical response.
A malfunctioning fuel injector will cause a severe cylinder misfire. This should be addressed immediately to prevent drivability issues and potential damage to the catalytic converter.
Common symptoms
- Illuminated or flashing Check Engine Light
- Engine misfire or rough idle
- Noticeable lack of engine power during acceleration
- Decreased fuel economy
- Engine stalling or hesitation
Likely causes
- Faulty fuel injector on cylinder 1
- Damaged, broken, or disconnected wiring in the cylinder 1 injector harness
- Corroded or loose electrical connector at the cylinder 1 injector
- Open or shorted circuit between the PCM and the injector
- Failing Powertrain Control Module (PCM) or injector driver (rare)
What to check before replacing parts
Perform a visual inspection of the cylinder 1 injector wiring and connector
Look for: Look for disconnected plugs, frayed wires, melted insulation, or corrosion at the cylinder 1 injector connector.
Listen to the injector operation
Look for: Use a mechanic's stethoscope to listen for a rhythmic clicking sound from the cylinder 1 injector while the engine is running; silence indicates it is not firing.
Test the injector resistance
Look for: Use a multimeter to measure the resistance (ohms) across the injector terminals. An infinite reading (OL) or a reading outside factory specifications indicates an internally open or shorted injector.
Check for power and ground signals using a noid light
Look for: Plug a noid light into the injector harness connector while cranking the engine. A flashing light confirms the PCM is sending the proper signal and the circuit is intact.
Perform a continuity test of the wiring harness
Look for: Use a multimeter to check for continuity between the injector connector and the PCM pins. High resistance or no continuity indicates a wiring harness failure.
This page explains the generic P0201 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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