# P0261: Cylinder 1 Injector "A" Circuit Low **Verdict:** Drive to a shop this week Fuel and air metering - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$1,100 - **Urgency:** This week - **Most likely:** Control wire shorted to ground or lost power - **DIY?:** Steps 1-3 ## Quick answer P0261 means the engine computer sees a voltage that is too low on the control circuit for the cylinder 1 fuel injector. That usually points to a control wire shorted to ground, a lost power feed or a shorted injector. Depending on the fault, cylinder 1 may get no fuel or too much, so the engine often misfires. ## What does P0261 mean? A port fuel injector normally has two wires. One brings 12 volts from a fuse or relay, and the other runs to the engine computer, which completes the circuit to ground for a few milliseconds to spray fuel. Between pulses, the control wire should sit near battery voltage because power flows through the closed injector. The "A" in the title refers to the first or only injector serving cylinder 1, since some engines use two per cylinder. Direct-injection systems use different drive circuits, but the code means the same thing. P0261 sets when the computer sees the control wire voltage lower than expected while the injector should be off. A wire shorted to ground or a missing power feed both pull it low. Some computers also flag an injector drawing excessive current. Electrical faults like this usually set the code on the first trip. Makers split the details between P0201, P0261 and P0262 differently, so a wiring diagram for your vehicle matters. ## What are the symptoms of P0261? - Check engine light on, usually alongside P0301 for cylinder 1 - Rough idle and loss of power from a dead or flooded cylinder 1 - Strong fuel smell or hard starting if the injector is stuck open - Engine stalling or stumbling on acceleration ## What causes P0261? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Injector control wire shorted to ground** (most common). If the insulation on the control wire wears through against the engine, a bracket or the block, the wire is grounded all the time. On many port systems that can hold the injector open with the key on, flooding cylinder 1. Harnesses disturbed during intake, valve cover or spark plug work, or chewed by rodents, are frequent sources. 2. **Lost power feed to the injector** (common). If the 12-volt supply to cylinder 1 is broken, the control wire has no voltage between pulses and reads low. A blown fuse, failed relay or broken splice can do this. When several cylinders share the feed, codes for other injectors usually appear too. Checking for voltage at the connector with the key on quickly separates power from control faults. 3. **Shorted injector winding** (common). Heat and age can break down the insulation inside the injector coil, lowering its resistance. The injector then draws too much current, which some computers detect as a low circuit, and it may also stick or leak. Measuring resistance across the injector terminals and comparing it with the specification for your engine shows whether the coil is shorted. 4. **Water or corrosion in the connector** (less common). Water from a hood seal leak, engine washing or a cracked connector can bridge the injector pins or corrode them, creating a path to ground. This is more common on older vehicles in wet or salty climates. Green crust on the pins or a cracked connector body are visible clues, and the fault may come and go with weather. 5. **Engine computer injector driver fault** (rare). The driver transistor inside the computer can fail shorted, grounding the control wire internally. That often follows a shorted injector or wiring fault that overloaded it, so fix the original short first or a new computer may fail too. Suspect the computer only when the wire tests clean with the computer unplugged and the problem persists once reconnected. ## How do you diagnose P0261? 1. Read all codes; injector codes on several cylinders point to a shared fuse, relay or feed. 2. With the key on and the injector plugged in, measure voltage on both injector wires; both should be near battery voltage. 3. Unplug the injector and measure its resistance against the specification for your engine. 4. With the computer connector unplugged, check the control wire for continuity to ground. 5. If the engine has been flooding, check the oil for a fuel smell and the spark plug for wetness before restarting repeatedly. ## How do you fix P0261, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Repair shorted or broken wiring | $100-$350 | Repair the damaged section and secure it away from sharp edges. | | Replace cylinder 1 fuel injector (port injection) | $200-$550 | Higher when the intake manifold must be removed. | | Replace cylinder 1 fuel injector (direct injection) | $400-$1,100 | New seals are required; some makers also require coding. | | Repair or replace engine computer | $700-$1,800 | Only after the short that damaged it is found and fixed. | Full price breakdowns: [fuel injector replacement cost](/cost/fuel-injector-replacement), [oil change cost](/cost/oil-change). ## Is it safe to drive with P0261? > **Drive to a shop this week.** Drive only gently and only to a shop. If you smell fuel, the engine is hard to start or it runs very rough, stop driving and have it towed, because a stuck-open injector can flood the cylinder, thin the oil with fuel and overheat the catalytic converter. ## Will P0261 fail an emissions test? P0261 keeps the check engine light on, so the car fails an OBD-based emissions test in most states. A flooded or dead cylinder also raises hydrocarbon emissions and can harm the catalytic converter. After the repair, clearing the codes resets the readiness monitors, so drive normally for several days before going back for a retest. ## After the repair: clearing P0261 Clear the codes, start the engine and listen for a smooth idle. With a scan tool, confirm the cylinder 1 misfire counter stays near zero and fuel trims for that bank look normal. If the cylinder flooded, consider an oil change, since fuel thins the oil. Drive several days; if P0261 and P0301 stay away, it is fixed. ## How to prevent P0261 - Route and clip the injector harness carefully after any work on top of the engine. - Fix leaking hood or cowl seals so water does not pool on injector connectors. - Avoid aiming a pressure washer directly at injector and other engine bay connectors. - Find the cause of any blown injector fuse instead of just replacing it. - Use rodent deterrents if the car is parked outside or in a barn for long periods. ## Codes often seen with P0261 - [P0201](/codes/p0201): Injector Circuit/Open - Cylinder 1 - [P0301](/codes/p0301): Cylinder 1 Misfire Detected - [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected - [P0172](/codes/p0172): System Too Rich (Bank 1) - [P0420](/codes/p0420): Catalyst System Efficiency Below Threshold (Bank 1) ## Frequently asked questions ### Can I drive with a P0261 code? Only gently, and only as far as a shop. Depending on the fault, cylinder 1 may get no fuel or may be flooded with it. If you smell fuel, the engine runs very rough or it is hard to start, stop driving and have it towed to protect the engine and converter. ### What does injector circuit low mean? It means the voltage on the injector control wire is lower than the computer expects when the injector should be off. Normally that wire sits near battery voltage between pulses. A wire shorted to ground, a missing power feed or a shorted injector coil can all pull it low. ### How much does it cost to fix P0261? Most P0261 repairs cost $100 to $1,100 at an independent shop. A wiring repair runs about $100 to $350, a port fuel injector $200 to $550 installed and a direct-injection injector $400 to $1,100. If the computer's injector driver is damaged, replacement and programming run $700 to $1,800. ### What is the difference between P0201 and P0261? Both are electrical faults on the cylinder 1 injector circuit. P0201 usually means an open circuit, such as a broken wire or injector coil. P0261 means the circuit voltage is too low, which often points to a short to ground or a missing power feed. Makers define the details differently. ### Can P0261 flood the engine? Yes, it can on many port-injected engines. If the control wire is shorted to ground, the injector may stay open whenever the key is on, pouring fuel into cylinder 1. That can cause hard starting, a fuel smell, fuel-diluted oil and, in severe cases, engine damage. Avoid repeated cranking. ### Can I fix P0261 myself? You can handle the first checks with a multimeter: confirm voltage at the injector, measure injector resistance and look for chafed wires. Repairing an accessible wire or replacing a port injector is a moderate job. Direct-injection systems run at very high pressure and voltage, so they are best left to a shop. ### Will a bad fuel injector cause P0261? Yes, an injector with a shorted coil can set P0261. Its resistance drops, so it draws more current than normal, and some computers read that as a low circuit. Measure resistance at the injector terminals; a reading well below the specification means the injector should be replaced. ### Should I change the oil after P0261? If the engine smelled of fuel, started hard or ran very rich, an oil change is a good idea. A leaking or stuck-open injector can wash fuel past the piston rings into the oil, thinning it. Check the dipstick for a fuel smell or a rising oil level after the repair. ### Will P0261 pass an emissions test? No, a car with P0261 and the check engine light on fails an OBD-based emissions test in most states. The cylinder 1 misfire also raises emissions. Repair the circuit, clear the codes and drive several days so the readiness monitors complete before you schedule a retest. ### Can a bad engine computer cause P0261? It can, but it is rare. The injector driver inside the computer can fail shorted, usually after a shorted injector or wire overloaded it. Rule out the wiring and injector first. If you replace the computer without fixing the original short, the new one can be damaged as well. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) ## Other fuel and air metering codes - [P0171 System Too Lean (Bank 1)](https://diagxcar.com/codes/p0171) - [P0172 System Too Rich (Bank 1)](https://diagxcar.com/codes/p0172) - [P0174 System Too Lean (Bank 2)](https://diagxcar.com/codes/p0174) - [P0175 System Too Rich (Bank 2)](https://diagxcar.com/codes/p0175) - [P0201 Injector Circuit/Open - Cylinder 1](https://diagxcar.com/codes/p0201) - [P0217 Engine Coolant Over Temperature Condition](https://diagxcar.com/codes/p0217) - [P0230 Fuel Pump Primary Circuit](https://diagxcar.com/codes/p0230) - [P0299 Turbocharger/Supercharger "A" Underboost Condition](https://diagxcar.com/codes/p0299) ## Symptoms - [Why is my car idling rough?](https://diagxcar.com/symptoms/rough-idle) - [Why does my car smell like gas?](https://diagxcar.com/symptoms/car-smells-like-gas) - [Why does my car crank but not start?](https://diagxcar.com/symptoms/car-cranks-but-wont-start) - [Why does my car stall while driving?](https://diagxcar.com/symptoms/car-stalls-while-driving) ## Repair costs - [Fuel injector replacement cost](https://diagxcar.com/cost/fuel-injector-replacement): $300-$1,500 - [Oil change cost](https://diagxcar.com/cost/oil-change): $45-$150 --- Source page: https://diagxcar.com/codes/p0261 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.