Loose or corroded cylinder 1 injector connector (OBD-Codes.com says this was the cause the majority of the time in its author's experience). Open or short in the cylinder 1 injector wiring harness. Dirty or plugged cylinder 1 fuel injector. Failed cylinder 1 fuel injector. Poor ground (RepairPal lists this as something often missed when an injector is replaced).

Clean or repair the cylinder 1 injector connector. Repair the open or shorted wiring in the cylinder 1 injector circuit, or fix a poor ground. Clean the cylinder 1 injector if it is dirty or plugged (OBD-Codes.com describes a pressurized injector-cleaner flush through the fuel rail test port on gasoline engines). Replace the cylinder 1 fuel injector if testing shows it has failed or cleaning doesn't help.

P0261⛽ Fuel injection / injector circuitStop and fix promptly

P0261: Cylinder 1 Injector Circuit Low (Meaning, Causes, Fixes)

Q: What does P0261 mean?

P0261 means the engine computer has seen a low-voltage condition in the electrical circuit for the cylinder 1 fuel injector. OBD-Codes.com says a loose or corroded injector connector is the most common cause, followed by a dirty, plugged or failed injector or an open or short in the injector wiring. RepairPal adds that shops often replace the injector or the computer when the real problem is wiring, connections or a poor ground. Fuel injectors are small electrically operated valves that spray fuel into each cylinder. OBD-Codes.com explains that on a typical engine the injectors get power through the fuel pump relay whenever the key is on, and the engine computer (PCM) fires each injector by switching its ground on for the right length of time. RepairPal describes the same thing in terms of the PCM's injector 'drivers', special transistors that turn the injectors on and off, and says P0261 sets when the voltage in the cylinder 1 injector circuit is too low, meaning the PCM can't properly control that injector. 'Cylinder 1' here refers to the cylinder numbered 1 by the manufacturer. The code is generic to OBD-II vehicles, but OBD-Codes.com notes the repair procedure varies by make. Search interest shows it often comes up on Ford 6.0L and 7.3L Power Stroke diesels and on Harley-Davidson motorcycles, so check technical service bulletins (TSBs) and the factory procedure for your vehicle.

Q: Can I keep driving with P0261?

Stop and fix promptly. Get it diagnosed soon. RepairPal rates P0261 'Urgent', meaning it can cause severe damage, and OBD-Codes.com says it should be diagnosed and repaired as soon as possible. A cylinder 1 injector that isn't working properly can make the engine run rough, lose power and run lean in that cylinder, which OBD-Codes.com says can lead to detonation (engine knock). If the check engine light is flashing, the engine shakes badly, or you smell raw fuel, keep driving to a minimum and have it checked. Fuel systems are under pressure, so don't open fuel lines with the engine running and let the engine cool before working near it.

Reviewed 2026-10-26 · Based on 2 cited source(s)

What P0261 means

Fuel injectors are small electrically operated valves that spray fuel into each cylinder. OBD-Codes.com explains that on a typical engine the injectors get power through the fuel pump relay whenever the key is on, and the engine computer (PCM) fires each injector by switching its ground on for the right length of time. RepairPal describes the same thing in terms of the PCM's injector 'drivers', special transistors that turn the injectors on and off, and says P0261 sets when the voltage in the cylinder 1 injector circuit is too low, meaning the PCM can't properly control that injector. 'Cylinder 1' here refers to the cylinder numbered 1 by the manufacturer. The code is generic to OBD-II vehicles, but OBD-Codes.com notes the repair procedure varies by make. Search interest shows it often comes up on Ford 6.0L and 7.3L Power Stroke diesels and on Harley-Davidson motorcycles, so check technical service bulletins (TSBs) and the factory procedure for your vehicle.

Severity: can I keep driving?

Stop and fix promptly

Get it diagnosed soon. RepairPal rates P0261 'Urgent', meaning it can cause severe damage, and OBD-Codes.com says it should be diagnosed and repaired as soon as possible. A cylinder 1 injector that isn't working properly can make the engine run rough, lose power and run lean in that cylinder, which OBD-Codes.com says can lead to detonation (engine knock). If the check engine light is flashing, the engine shakes badly, or you smell raw fuel, keep driving to a minimum and have it checked. Fuel systems are under pressure, so don't open fuel lines with the engine running and let the engine cool before working near it.

Common symptoms

Check engine light on
Engine runs rough or misfires (OBD-Codes.com says rougher than normal; RepairPal says misfire and rough idle in some cases)
Lack of power (listed by OBD-Codes.com)
Worse fuel economy (OBD-Codes.com says a big drop; RepairPal says poor fuel economy in some cases)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Loose or corroded cylinder 1 injector connector (OBD-Codes.com says this was the cause the majority of the time in its author's experience)
Open or short in the cylinder 1 injector wiring harness
Dirty or plugged cylinder 1 fuel injector
Failed cylinder 1 fuel injector
Poor ground (RepairPal lists this as something often missed when an injector is replaced)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes. Other injector circuit codes (such as P0264, P0267 or P0270) appearing together can point to a shared wiring, power or ground problem rather than one bad injector.
Look up technical service bulletins for your year, make and model.
Inspect the cylinder 1 injector connector, as OBD-Codes.com describes: check that it is secure, then remove it and look for corrosion, pushed-out pins or bent injector terminals. Fix any damage and add dielectric grease before reconnecting.
On a gasoline engine, OBD-Codes.com suggests listening to the injector with a long screwdriver (handle to your ear) while the engine runs. A clear clicking means it is firing; no clicking means no power or a failed injector.
Clear the code and see if it returns. If it comes back after the connector checks out, the circuit or injector needs testing.

Typical fixes

Clean or repair the cylinder 1 injector connector
Repair the open or shorted wiring in the cylinder 1 injector circuit, or fix a poor ground
Clean the cylinder 1 injector if it is dirty or plugged (OBD-Codes.com describes a pressurized injector-cleaner flush through the fuel rail test port on gasoline engines)
Replace the cylinder 1 fuel injector if testing shows it has failed or cleaning doesn't help

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

OBD-Codes.com describes checking for power at the injector harness connector with a voltmeter: no power points to the wiring or connection back to the fuel pump relay. If power is there and the PCM's injector driver is working, the meter shows rapid pulses across the connector terminals, and OBD-Codes.com says the injector should then be replaced
The sources differ in emphasis: OBD-Codes.com puts loose or corroded connectors first and says shorted or open wiring is rare when left undisturbed, while RepairPal warns that the injector or PCM is often replaced when the real problem is wiring, connections or a poor ground
Diesel engines (such as Ford Power Stroke) use high-pressure injection systems that work differently from the gasoline layout our sources describe; testing and repair on those is best left to a shop with the right scan tool and factory procedure
The code returns after the connector and wiring have been repaired, or several injector circuit codes set at once

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0261?

Only as much as you need to. RepairPal rates it 'Urgent', and OBD-Codes.com says to diagnose and repair it as soon as possible because a misbehaving injector can cause rough running, power loss and detonation. If the engine shakes badly or the check engine light flashes, limit driving and get it checked.

Is P0261 always a bad injector?

No. OBD-Codes.com says loose or corroded connectors caused this kind of fault most of the time in its author's experience, and RepairPal warns that injectors are often replaced when the real problem is wiring, connections or a poor ground. Check the connector and wiring before buying an injector.

What's the difference between P0261, P0262 and P0263?

P0261 is a low-voltage fault in the cylinder 1 injector circuit, and P0262 is the matching high-voltage fault. P0263 is different: it means cylinder 1 is contributing less power than the others, which usually points to a fuel delivery problem rather than a circuit fault.

Why do P0261, P0264, P0267 and P0270 show up together?

Our sources don't cover this combination directly. Since each of those codes is an injector circuit low fault for a different cylinder, several at once suggests looking for something the circuits share, such as power, ground, a harness connector or the module that drives the injectors, before replacing individual injectors.

Sources

Last reviewed 2026-10-26. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.