What it means
Cylinder 1 Injector Circuit Low: the signal voltage is below the expected range. This affects fueling of the associated cylinders.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module switches and monitors the injector circuit for cylinder 1 to deliver fuel to that cylinder. P0261 sets when the circuit signal is lower than expected, which can interrupt cylinder 1 fueling and cause a misfire.
Common causes
Most likely first.
- Injector winding failed open
- Wiring or connector fault
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light on
- Rough running or misfire
- Reduced engine power
- Hard starting
How to diagnose it
- Record freeze-frame data and check misfire counts for cylinder 1 to confirm when the injector fault occurs.
- With the engine off, inspect the cylinder 1 injector connector for corrosion, loose fit, damaged wiring, or backed-out pins.
- Check the cylinder 1 injector circuit for a short to ground, damaged wiring, or poor terminal contact using the manufacturer's diagram.
- Measure the cylinder 1 injector winding and compare it with the manufacturer's specification, taking care not to damage the connector.
- If wiring and injector checks pass, test the injector driver circuit at the engine control module using the manufacturer's procedure.
Common fixes
- Reseat the cylinder 1 injector connector and repair loose terminals.
- Repair damaged wiring or corroded contacts in the cylinder 1 injector circuit.
- Replace the cylinder 1 injector if its winding fails the specified test.
- Repair the injector driver circuit if testing confirms an engine control module fault.
Can I keep driving?
A cylinder 1 misfire can reduce power and allow unburned fuel into the exhaust, which may damage the catalytic converter. Avoid hard driving and stop if the engine runs severely rough or the warning light flashes.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.