P0291
Cylinder 11 Injector Circuit LowP0291 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 11 Injector Circuit Low. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0291 means
P0291 is stored when the engine control module (ECM) detects a voltage or current level at the cylinder 11 fuel injector circuit that falls below the manufacturer's calibrated minimum threshold. The ECM supplies a regulated voltage pulse to each injector's solenoid; if the return signal or supply voltage for cylinder 11's injector reads consistently low, the ECM logs P0291 and illuminates the MIL. This fault is exclusive to engines with 11 or more cylinders — primarily V12 and W12 platforms such as the BMW N73/N74 V12 (7-series, Rolls-Royce Ghost/Phantom), Mercedes-Benz M120/M275/M279 V12, Ferrari/Lamborghini V12 engines, and the Volkswagen/Audi W12 (Phaeton, A8L W12, Bentley Continental GT).
The most frequent physical cause is a corroded or loose injector connector; moisture ingress into the harness plug creates resistance that drops the apparent circuit voltage below threshold. An internally open-coil injector, a wiring break in the harness between the ECM and the injector, or a blown injector fuse can all produce the same low-signal result. ECM driver failures are uncommon but must be ruled out after the wiring and injector itself are confirmed good.
Because cylinder 11 receives little or no fuel when this fault is active, the affected cylinder misfires continuously, raw fuel enters the exhaust stream, and the catalytic converter is at risk of heat damage. Diagnosis should begin with a visual inspection of the connector and wiring before any parts are replaced.
Common causes
Most-frequently reported root causes when P0291 is logged.
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1
Corroded, loose, or pushed-out pins in the cylinder 11 injector harness connector.
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2
Open circuit or break in the wiring between the ECM and the cylinder 11 injector.
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3
Failed fuel injector with an internally open solenoid coil producing no or very low resistance.
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4
Blown fuse or failed relay in the fuel injector power supply circuit.
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5
Short circuit to ground in the injector signal wire reducing measured voltage.
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6
Poor ECM ground connection causing an overall low-reference voltage condition.
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7
Faulty ECM injector driver transistor for cylinder 11 unable to supply correct voltage.
Symptoms drivers notice
How to diagnose P0291
A typical diagnostic flow when this code is present.
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1
Retrieve all stored DTCs and freeze-frame data; note any companion misfire or injector codes.
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2
Inspect the cylinder 11 injector connector for corrosion, bent pins, or moisture — clean or repair before further testing.
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3
Check all fuel-injection-related fuses and relays in the fusebox; replace any that are blown.
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4
Measure injector coil resistance with a multimeter; compare to OEM specification (typically 12–16 Ω high-impedance or 1–5 Ω low-impedance for diesel piezo types).
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5
Use a multimeter or oscilloscope to verify supply voltage at the injector connector with ignition on (should be near battery voltage before activation).
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6
Perform a wiring continuity and insulation test on the harness from the ECM connector pin to the injector plug; look for opens or shorts to ground.
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7
If wiring and injector test good, command the cylinder 11 injector via scan tool or noid-light and test ECM driver output before concluding an ECM fault.
Related powertrain codes
- P0065 — Air Assisted Injector Control Range/Performance
- P0066 — Air Assisted Injector Control Circuit or Circuit Low
- P0067 — Air Assisted Injector Control Circuit High
- P0087 — Fuel Rail/System Pressure - Too Low
- P0088 — Fuel Rail/System Pressure - Too High
- P0089 — Fuel Pressure Regulator 1 Performance
Frequently asked questions
Which engines can generate P0291?
Only engines with 11 or more cylinders: V12s (BMW N73/N74, Mercedes M120/M275/M279, Ferrari, Lamborghini), W12s (VW/Audi/Bentley), and specialty inline engines with twin injectors per cylinder (e.g. Cummins ISX with dual injector strategy). Standard V8 or V6 engines cannot set this code.
Is P0291 the same as a cylinder 11 misfire code?
No. A misfire code (e.g. P030B for cylinder 11) confirms combustion failure detected via crankshaft dropout. P0291 specifically flags a low electrical condition in the injector circuit; the cylinder may or may not misfire if the injector is still partially functional, but both codes often appear together.
Can I clear P0291 by just cleaning the injector?
P0291 is an electrical fault, not a flow fault. Injector cleaning addresses clogging but will not fix an open coil, broken wire, or corroded connector. Check wiring and connector condition first; if the injector coil resistance is out of spec, replacement is required.
How urgent is the repair?
Fairly urgent. With cylinder 11 misfiring continuously, unburnt fuel enters the exhaust and can damage the catalytic converter within a few hundred miles. On expensive V12 platforms the converter replacement cost often exceeds the injector or wiring repair cost, making prompt diagnosis worthwhile.
Disabling P0291 in software
RaceTune can permanently disable P0291 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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