OBD-II trouble code
P0262: Cylinder 1 Injector Circuit High
An open or voltage-shorted control circuit on the number one injector. Cylinder 1 sits under the front of the engine on most layouts, so this is the injector connector that gets rained on by a weeping water pump or front seal — check for oil and coolant staining before condemning anything.
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
Browse every code in P0200–P0299, or start from the full code library.
What does P0262 mean?
An injector is switched by grounding it. Battery voltage sits waiting on one terminal and the control module completes the circuit by pulling the other terminal to ground for a few milliseconds. While it does that, it watches the control wire and expects to see it collapse to near zero volts. This code is stored when the module commands the number one injector on and the wire refuses to come down — or, on some systems, when the current it senses is above the plausible range.
A wire that will not pull down is either not connected to anything the module can sink current through, or it is being held up by a voltage source. So the fault list divides into open circuits — a broken conductor, a pin that has backed out of its housing, or an injector winding that has gone open internally — and shorts to battery voltage, where a chafed conductor is touching something live. Either way the cylinder gets no fuel, and a dead cylinder pumps its full charge of air and any residual fuel straight into the exhaust.
Where cylinder 1 differs from the rest of the block is what is physically above and around it. On an inline engine it sits at the front, right behind the accessory drive, the front cover and the water pump. That is the wettest, dirtiest corner of the engine bay. A water pump seeping, a front crankshaft seal weeping, a leaking cam cover corner or a failed thermostat housing all put fluid onto that end of the head — and coolant is the worst of them, because it does not simply sit there. Coolant wicks into a connector, corrodes the terminals, and produces exactly this fault while the wiring itself looks perfectly sound from the outside. So the very first thing to look for on this code is staining. Dried coolant crust, oil-soaked loom tape or a clean stripe washed through road grime above the number one injector is worth more than any meter reading, because it tells you the fault has a cause that will come back if only the connector is cleaned.
There is a second thing worth knowing about this particular cylinder. Number one is the engine's reference — top dead centre on cylinder 1 is the datum for the firing order, for cam and crank correlation, and for every timing procedure in the manual. Because of that, cylinder 1 is the cylinder people have had apart most recently. Timing belt and chain jobs, front cover reseals and water pump replacements all involve moving that end of the injector harness, and a lead pinched under a bracket or a connector left half-seated during reassembly produces this code within a few hundred miles. If the light appeared after front-of-engine work, start with routing and connector seating rather than with parts.
The practical advantage of this cylinder is access. On most engines number one is the easiest injector to reach, which makes the swap test cheap: move the number one injector to another cylinder and move that one across. If the code follows the injector, the injector is at fault; if it stays on cylinder 1, the fault is in the harness or the module. Very few faults can be split that cleanly for the cost of two clips.
Do not keep driving it. Unburned mixture entering a hot catalytic converter is how a wiring repair becomes a converter replacement, and a flashing light means damage is happening now rather than eventually.
Common causes
- Coolant from a weeping water pump, thermostat housing or hose wicking into the number one injector connector and corroding its terminals
- Oil from a front cam cover corner or crankshaft seal soaking the loom and connector at the front of the head
- Broken control wire between the module and the number one injector
- Pin backed out or unseated in the injector connector, often after front-of-engine work
- Open winding inside the number one injector
- Control wire chafed against a bracket and shorted to a battery-voltage circuit
- Harness pinched or trapped during timing belt, chain or front cover work
- Blown fuse or open supply feed on the injector power side
- Failed injector driver inside the module, which is uncommon and should be a measured conclusion
Symptoms
- Check engine light, flashing if the misfire is severe enough to threaten the converter
- A cylinder 1 misfire code stored alongside, and pronounced shaking at idle
- Clear loss of power and hesitation under acceleration
- Smell of unburned fuel from the exhaust
- Extended cranking or a rough start
- Visible coolant staining, crust or oil wetness around the front of the cylinder head
- The fault appearing shortly after timing, front cover or water pump work
- Idle that improves slightly as the engine warms but never becomes smooth
Diagnostic steps
- 1.Look before you measure. Inspect the number one injector connector and the loom above it for coolant crust, oil soaking and washed-clean stripes that show where fluid has been running.
- 2.If fluid is present, find its source — water pump, front seal, thermostat housing or cam cover corner — because cleaning the connector without fixing the leak buys a few months at most.
- 3.Ask what work has been done recently. Front-of-engine jobs disturb this harness, and a pinched lead or half-seated connector is a very common cause here.
- 4.Unplug the injector and measure its coil resistance. An open or very high reading condemns it; a normal reading moves the search to the harness.
- 5.Check for battery voltage at the injector's supply terminal with the key on. Nothing there means a fuse or supply fault rather than an injector fault.
- 6.With both ends disconnected, check continuity of the control wire from the injector connector back to the module pin.
- 7.Check the control wire against ground with the key on and everything unplugged, to catch a short to battery voltage holding the circuit high.
- 8.Use the accessibility of this cylinder: swap the number one injector with one from another cylinder and see whether the code follows the part or stays with the position.
- 9.Confirm the module is producing a drive pulse with a noid light or scan tool injector test before considering the driver circuit.
Repair cost
$50 – $1,500
Cleaning and repairing a corroded connector is $75 to $250, but on this cylinder it is often only half the job — the leak that soaked it has to be dealt with, and a water pump or front cover reseal is $350 to $900 on many engines. A single injector is $60 to $400 in parts plus half an hour to three hours of labour, and cylinder 1 usually sits at the easy end of that range. A harness repair is $100 to $300. A failed module driver is uncommon at $500 to $1,500 with programming and should never be assumed. The expensive outcome this code causes if ignored is a catalytic converter at $500 to $2,500, poisoned by unburned mixture from a dead cylinder.
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.