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P0261: Cylinder 1 Injector Circuit Low

Severe

Quick answer

P0261 means the engine computer detected voltage lower than expected in the cylinder 1 injector control circuit, usually a short to ground, a corroded connector, or a shorted injector solenoid. It’s the more specific cousin of P0201: same circuit, but the fault direction is known. Start at the connector, then measure the injector’s resistance.

What it means

The ECM fires the cylinder 1 injector by grounding its control circuit for a precise number of milliseconds, and it watches the circuit’s voltage the whole time. P0261 sets when that voltage sits lower than it should: the circuit is being pulled toward ground when the computer isn’t doing the pulling, or the solenoid is drawing far more current than a healthy winding allows.

“Low” narrows the hunt compared with the generic circuit code P0201: current is escaping to ground somewhere. A wire chafed through to bare metal, a wet or corroded connector, or injector windings shorted internally all produce it. A hard short on the control side can even hold the injector open, flooding cylinder 1, fouling its spark plug, and washing fuel past the rings, while a current overload usually makes the ECM shut that driver off entirely, leaving the cylinder dead.

Either way the cylinder stops burning properly, so a misfire code (P0301) often rides along. This is a multimeter diagnosis, not a parts-cannon one: the injector, its two-pin connector, and the harness between it and the ECM are the entire suspect list.

P0261 symptoms: what you'll notice

  • A steady miss from cylinder 1: rough, rhythmic shaking at idle and stumbling under acceleration.
  • A strong fuel smell or a fouled, soaked spark plug if the short is holding the injector open and flooding the cylinder.
  • A check engine light that may flash: a dead or flooded cylinder dumps unburned fuel into the exhaust and overheats the catalytic converter.
  • Worse fuel economy and, in flooding cases, hard starts or a hydrocarbon-rich exhaust smell.

Common causes

Ordered from most to least likely.

  1. 1.

    Injector solenoid shorted internally

    Shorted windings read well below spec on a multimeter, comparing against a neighboring injector makes the bad one obvious.

  2. 2.

    Control wire chafed to ground

    The harness rubbing through on the fuel rail, a bracket, or the valve cover edge grounds the circuit permanently.

  3. 3.

    Corroded or wet injector connector

    Moisture or green crust bridging the pins leaks current to ground; common after engine washes or coolant leaks.

  4. 4.

    Weak supply voltage to the injector

    A corroded feed circuit drops the whole circuit’s voltage: suspect it if several injectors set low codes together.

  5. 5.

    ECM driver fault

    Rare: conclude this only after the injector and wiring both test good.

How to fix it: diagnosis, step by step

Cheapest and most likely checks first.

  1. 1 Scan for the pattern

    Read all codes with freeze frame. P0261 alone points at cylinder 1’s injector or wiring; several low codes at once point at shared supply. Note whether P0301 or the contribution code P0263 accompanies it.

  2. 2 Inspect the connector and harness

    Unplug the cylinder 1 injector connector: look for corrosion, moisture, bent pins, and a loose lock, then follow the harness toward the ECM checking for chafe spots against metal. This free step solves a real share of low-circuit codes.

  3. 3 Measure resistance against a neighbor

    With the connector off, measure across the injector pins and compare with the next cylinder over. Typical port injectors read roughly 11–16 Ω; a reading well below the neighbor’s condemns the cylinder 1 injector’s windings.

  4. 4 Check the control wire for a short to ground

    With the connector and the ECM side isolated, check continuity between the control wire and chassis ground. Continuity means the harness (not the injector) is your fault.

  5. 5 Swap-test the injector

    If access allows, swap the cylinder 1 injector with a neighbor and clear codes. If the low code moves to the new cylinder, replace the injector; if it stays on cylinder 1, the wiring or driver is at fault.

Parts & tools you may need

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Related codes

Frequently asked questions

What does code P0261 mean?
P0261 means the engine computer detected voltage lower than expected in the cylinder 1 injector control circuit, usually a short to ground, a corroded connector, or a shorted injector solenoid. It’s serious: diagnose it promptly to avoid expensive damage.
What’s the difference between P0261 and P0201?
P0201 says “something is electrically wrong in cylinder 1’s injector circuit”; P0261 adds the direction: the voltage is too low, meaning current is leaking to ground or the solenoid is shorted. Same suspects, but the low code lets you test for shorts specifically instead of everything.
Is it the injector or the wiring?
Two five-minute multimeter checks decide it: resistance across the injector pins (compare with a neighbor, a much lower reading condemns the injector) and continuity from the control wire to ground with everything unplugged (continuity condemns the harness).
Can I drive with P0261?
Treat it like an active misfire: minimal, gentle driving only. A dead cylinder, or worse, a flooding one: sends raw fuel into the exhaust, and the catalytic converter it destroys costs far more than any likely fix here.
Will injector cleaner fix P0261?
No. Cleaners address flow restrictions inside the injector; this code reports an electrical fault. No additive repairs a shorted winding or a chafed wire.
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