OBD-II trouble code
P0261: Cylinder 1 Injector Circuit Low
The engine computer saw the cylinder 1 fuel injector control circuit read low — usually a wire shorted to ground or a shorted injector coil. Cylinder 1 typically misfires, so diagnose it before the catalytic converter is damaged.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $50 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0261 mean?
Each fuel injector has battery voltage on one side and the engine control module (ECM) switching the ground on the other. To fire the injector, the ECM pulls its control wire low for a precise number of milliseconds. Between pulses, that control wire should sit near battery voltage because it is not connected to anything conductive.
P0261 sets when the ECM sees the cylinder 1 control circuit reading low when it should be high. In practice that means the circuit is grounded when it should be floating: a control wire chafed through to the block or body, an injector with a shorted coil winding, or moisture and corrosion bridging pins inside the connector. Some manufacturers also set P0261 when the measured current on the circuit is out of range low.
Because the code is already isolated to cylinder 1, diagnosis is targeted. On an inline engine cylinder 1 is normally at the front, nearest the accessory belt and timing cover; on a V engine it is on Bank 1 by definition but the physical position varies by manufacturer, so confirm the layout in the service information. A shorted circuit usually means cylinder 1 is not being fueled correctly, so expect a misfire (often a companion P0301). Sustained misfire dumps raw air and unburned mixture into the exhaust and can overheat the catalytic converter, which is why this is worth fixing right away rather than driving on.
Common causes
- Cylinder 1 injector control wire chafed and shorted to ground
- Shorted coil winding inside the cylinder 1 injector
- Corrosion or moisture bridging terminals in the cylinder 1 injector connector
- Harness damage from heat near the exhaust manifold or from a prior repair
- Pinched wire under an intake manifold or valve cover after recent service
- Rarely, a failed cylinder 1 injector driver inside the ECM/PCM
Symptoms
- Check engine light on, sometimes flashing under load
- Rough idle and noticeable engine shake
- Misfire on cylinder 1, often with a companion P0301
- Loss of power and hesitation on acceleration
- Increased fuel consumption or a raw fuel smell
- Hard starting in some cases
Diagnostic steps
- 1.Confirm P0261 and record companion codes — a cylinder 1 misfire (P0301) or the paired high-circuit code P0262 changes the picture.
- 2.Locate cylinder 1 for your specific engine, then inspect its injector connector and pigtail for corrosion, melted insulation, and backed-out pins.
- 3.Disconnect the cylinder 1 injector and measure its coil resistance with the key off. Compare to specification and to the other injectors — a reading well below spec indicates a shorted coil.
- 4.With the injector unplugged and the ECM connector disconnected, check the control wire for continuity to ground. Any continuity confirms a short in the harness.
- 5.Wiggle-test the harness from the injector back toward the firewall while watching for a change, focusing on chafe points near the exhaust manifold and manifold studs.
- 6.Use a noid light or a scan tool injector test to confirm the ECM is pulsing the circuit normally once the wiring checks out.
- 7.If the injector, connector, and wiring all test good and the drive signal is still wrong, suspect the ECM's injector driver — verify with the manufacturer's pinout test before condemning the module.
Repair cost
$50 – $1,500
Repairing a chafed wire or corroded connector is often $75-$250. A single fuel injector runs $60-$400 in parts plus 0.5-3 hours of labor — a port injector on top of the intake is quick, while a direct-injection or lower-intake injector takes considerably longer. A failed ECM injector driver is uncommon and runs $500-$1,500 including programming. Diagnosis alone is typically $75-$150.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with fuel injector replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.