P0291 code: Cylinder 11 Injector Circuit Low
P0291 means cylinder 11 Injector Circuit Low. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0291 means
Cylinder 11 exists only on engines with eleven or more cylinders, so P0291 is effectively a V12 code (including W12-style layouts). It sets when the ECM measures voltage below the expected range on the cylinder 11 injector control circuit — the electrical signature of a short to ground, an open circuit, or an injector coil that has shorted internally. As with the whole P0261–P0296 family, this is a circuit diagnosis: a mechanically clogged injector would starve the cylinder without disturbing the voltage the ECM monitors, producing a misfire code instead. Twelve identical injector circuits make comparison testing the natural approach — resistance-check cylinder 11's injector against any neighbor and inspect its harness leg and connector. Companion codes are P0211 (cylinder 11 injector circuit) and P0311 (cylinder 11 misfire). Twelve-cylinder bank numbering differs by manufacturer, so identify cylinder 11's physical position from your engine's documentation before testing.
P0291 symptoms
- Misfire on cylinder 11 — often nearly imperceptible on a V12
- Faint idle unevenness or high-rpm coarseness
- Slight power and refinement loss
- Check-engine light, flashing under sustained misfire
- May be entirely symptom-free if intermittent
What it costs to fix P0291
Typical range: $60–$450 · about ~0.5–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Fuel injector (single) | $50–$300 | ~0.5–2 hrs |
| Wiring/connector repair | $5–$50 | ~0.5–2 hrs |
Twelve-cylinder engine bays are the tightest of all: expect labor at or beyond the top of the range once intake plumbing and covers come off, and direct-injection injectors for these engines carry premium pricing. Wiring repairs remain cheap in parts.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0291 for my exact vehicle →
How to fix P0291
Advanced — usually a shop job unless you’re well equipped
- Locate cylinder 11 on your twelve-cylinder engine
Only V12 and W12 engines have a cylinder 11, and the numbering varies between makers, so use the layout diagram rather than counting from the front. Check whether one module or two run the engine; on some dual-module designs each bank's injectors are controlled separately, and scanning both shows whether other cylinders on that bank are also reporting faults.
- Remove covers carefully and inspect the loom
On many V12s the injector connectors hide under engine covers or the intake plenum. Brittle, heat-aged plastic clips snap easily, and a broken clip can leave the harness resting on a hot or sharp surface — the very thing that grounds a control wire. Look for shiny wear marks and melted insulation along the cylinder 11 leg as you go.
- Measure injector 11 against the injectors beside it
Ohm injector 11 and a couple of its neighbours. A coil shorting internally reads clearly below the others; because injector resistance varies by design, the side-by-side comparison is more reliable than any generic figure. If 11 matches its neighbours, the injector is probably fine and the wiring becomes the focus.
- Check the control circuit for a short to ground
With the battery disconnected and both injector 11 and its module connector unplugged, measure the control wire to ground; it should read open. Take a fuel smell or a rich, flooding start on that bank seriously — a grounded control wire can leave the injector held open, and a cylinder full of fuel can hydrolock.
- Replace the injector, and leave module work to a specialist
Replace injector 11 if it tested low, with new seals throughout. If P0291 survives a new injector and a clean harness, the module's driver may have been damaged by the original short; on twelve-cylinder engines, module replacement typically needs programming and sometimes security coding, so involve a shop with dealer-level software.
DIY or shop? Rated advanced because of access, not the electrical logic: the tests are ordinary meter work, but on most twelve-cylinder engines just reaching injector 11 means removing covers, an intake plenum, or a fuel rail with single-use seals and gaskets. A skilled DIYer with the service manual can manage it. Most owners are better off doing the scan and visual checks themselves, then paying a shop that knows the engine for the teardown and any module work.
Tools for the DIY steps: Scan tool that reads every engine module · Digital multimeter · Trim and clip removal tools · Service manual for your engine · Injector seal and gasket kit
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0291.
Start a case with P0291 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0291?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0291: common questions
Why have I never heard of P0291?
Because very few engines can set it. Cylinder 11 exists only on twelve-cylinder (and similar) engines, so this code lives almost exclusively on luxury and performance V12s. On any smaller engine, a reported P0291 deserves skepticism about the scan data.
What does the ECM see before setting P0291?
Lower-than-expected voltage on the cylinder 11 injector circuit while pulsing it — consistent with a short to ground, broken wiring, or an injector coil shorted internally. The high-voltage version of the same monitor is P0292.
Can I ignore it since the car runs perfectly?
No — smooth running is exactly what a V12 does with a dead cylinder. Meanwhile unburned fuel is heating that bank's catalytic converter, and exhaust repairs on twelve-cylinder cars are notoriously expensive. Fix the cheap electrical fault before it creates a costly one.
How do I know if the injector or the harness failed?
Measure the cylinder 11 injector's resistance and compare with a neighbor. Matching values clear the injector and implicate the harness or connector; a shorted or open reading condemns the injector. On these engines, do the measurement before any teardown you can avoid.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0291 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0291 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.