Standardized generic DTCFuel & air metering / injector control

P0291 — Cylinder 11 Injector Circuit Low

P0291 is the standardized powertrain DTC for “Cylinder 11 Injector Circuit Low.” The code identifies the monitored condition; it does not by itself prove which part failed.

Standardized generic definition

Cylinder 11 Injector Circuit Low

DTC category

Fuel & air metering / injector control

Diagnostic priority

Moderate to high if the engine is misfiring. A leaking injector can also damage the catalyst or dilute engine oil.

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What P0291 means

P0291 is the standardized powertrain DTC for “Cylinder 11 Injector Circuit Low.” The code identifies the monitored condition; it does not by itself prove which part failed.

Start with the stored data and the simplest external checks before replacing the component named in the code.

How to interpret the code wording

“Circuit Low” means the module saw voltage or a signal below its calibrated range. Depending on circuit design, likely test paths include a short to ground, missing reference/supply voltage, excessive resistance, poor terminal contact, or a failed sensor/actuator. Verify the circuit diagram and measure the circuit before replacing the named component.

Possible symptoms

Cylinder misfire
Rough idle
Hard start
Fuel odor or poor economy
Check Engine Light

Causes to test

These are diagnostic possibilities, not a statistical parts-replacement ranking. Vehicle-specific service information takes priority.

Injector electrical open/short or poor connector contact
Injector mechanically clogged or leaking
Driver/control-circuit fault
Fuel-pressure problem
Mechanical compression issue mistaken for injector imbalance

Step-by-step diagnostic workflow

Identify the cylinder and save misfire/fuel-trim data.
Inspect injector connector and harness; verify supply and control with the correct test method.
Use injector balance, current-ramp, or contribution testing where specified.
Confirm fuel pressure and mechanical compression if the cylinder remains weak.
Perform circuit or mechanical tests specified by service information; repair the confirmed root cause.
Clear codes only after repair, then complete an appropriate drive cycle and verify the code and symptoms do not return.

Preserve evidence: EPA OBD guidance emphasizes that stored DTCs and freeze-frame data are important to proper diagnosis. Save them before clearing codes.

Scan data worth checking

Misfire counters
Injector command/pulse width
Fuel trims
Fuel/rail pressure
Cylinder contribution data where supported

Severity and drivability

Moderate to high if the engine is misfiring. A leaking injector can also damage the catalyst or dilute engine oil.

Stop driving and investigate immediately if there is a flashing MIL, oil-pressure warning, overheating, fuel leakage, severe misfire, major loss of power, abnormal mechanical noise, or a transmission that is slipping badly.

Common diagnostic mistakes

Using a test light that can overload a PCM injector driver
Replacing an injector without checking compression
Ignoring a leaking injector because electrical resistance tests normally

Related generic codes

P0290 — Cylinder 10 Contribution/Balance FaultP0292 — Cylinder 11 Injector Circuit HighP0289 — Cylinder 10 Injector Circuit HighP0293 — Cylinder 11 Contribution/Balance FaultP0288 — Cylinder 10 Injector Circuit LowP0294 — Cylinder 12 Injector Circuit Low

Source and accuracy notes

Generic DTC structure and standardized definitions are governed by SAE J2012/J2012DA. Actual enable criteria, thresholds, circuit pinouts, test values, software conditions, and repair procedures vary by vehicle. Use current OEM service information for the exact year/engine/calibration and check applicable manufacturer technical service bulletins. See the site methodology and primary-reference policy.