OBD codes / P0294
P0294
ModerateCylinder 12 Injector Circuit Low
The other eleven cylinders will carry the engine so convincingly you may doubt anything is wrong, but cylinder 12's unburned fuel is still working on that bank's catalytic converter. Repair promptly on the light alone, and stop driving if it begins to flash.
What this code means
P0294 covers the last injector on the largest common engine layout: it sets when the ECM measures below-expected voltage on the cylinder 12 injector control circuit, and only twelve-cylinder engines (V12 and W12 layouts) can generate it. The low-voltage fault pattern points to a short to ground in the wiring, an open circuit, or an injector coil that has shorted internally. Like the rest of this code family, it judges the electrical path exclusively — a clogged injector is a mechanical fuel restriction that leaves circuit voltage untouched and shows up as a misfire code instead. With eleven identical healthy circuits available for comparison, diagnosis is methodical: resistance-check cylinder 12's injector against a neighbor, inspect its connector, and swap-test if results are unclear. Companion codes are P0212 (cylinder 12 injector circuit) and P0312 (cylinder 12 misfire). Confirm cylinder 12's physical position from your engine's numbering diagram, as twelve-cylinder conventions differ across manufacturers.
Symptoms you might notice
- Misfire on cylinder 12, typically well-masked by the other eleven
- Slight coarseness at idle or under load
- Minor power and refinement loss
- Check-engine light, flashing if the misfire is sustained
- Possibly no symptoms at all when the fault is intermittent
What it costs to fix
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 |
Cylinder 12 usually sits at the rear of a bank in a densely packed twelve-cylinder bay — access labor tends toward and beyond the top of the range, and direct-injection injectors for these engines are premium-priced. The wiring-repair outcome is far cheaper.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0294 for my exact vehicle →
Frequently asked
Which engines can set P0294?
Only twelve-cylinder engines — V12s and W12-style layouts. There is no cylinder 12 on anything smaller, so this code simply cannot occur on four-, six-, eight-, or ten-cylinder vehicles.
Is P0294 a clogged injector?
No. A clog is mechanical and invisible to this monitor, which watches circuit voltage. P0294 means the cylinder 12 injector circuit read electrically low — short to ground, broken wire, or shorted injector coil. The fix is electrical, not a cleaning service.
Why fix it if the car drives beautifully?
Because a V12 masking the misfire doesn't stop the chemistry: unburned fuel from cylinder 12 can overheat that bank's catalytic converter, and exhaust repairs on twelve-cylinder cars cost multiples of an injector or harness fix. The warning light is the only symptom you may get.
What's the first test a shop will run?
Usually injector resistance: unplug cylinder 12's injector, measure it, and compare with a neighbor. That single measurement splits the problem — matching values send the diagnosis to the harness and connector, while a shorted or open reading condemns the injector itself.
Seeing P0294 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0294 for my vehicleRelated trouble codes
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Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.