P0212 code: Injector Circuit/Open - Cylinder 12
P0212 means injector Circuit/Open - Cylinder 12. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0212 means
P0212 is the highest-numbered generic injector circuit code: the engine computer detected an open circuit, a short, or out-of-range resistance in the wiring and coil that fire the cylinder 12 fuel injector. Only V12 engines have a twelfth cylinder, so this code is exclusive to twelve-cylinder luxury and performance vehicles. Like its eleven siblings, it describes an electrical failure — a clogged injector conducts electricity normally and would set misfire or fuel-trim codes instead. Diagnosis runs cheapest-first: verify the injector connector is fully seated and free of corrosion, inspect the long V12 harness for chafed or heat-hardened wiring, then resistance-test the injector's internal winding. Only after all of that checks out should the engine computer's driver stage come under suspicion, because it fails rarely. Expect the paired misfire code P0312 whenever cylinder 12 isn't firing.
P0212 symptoms
- Cylinder 12 misfire, typically stored with P0312
- Idle vibration a V12 owner will notice immediately — these engines are normally glass-smooth
- Loss of power and refinement under acceleration
- Check-engine light, possibly flashing during the misfire
- Hard starting in some cases
What it costs to fix P0212
Typical range: $100–$600 · 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 | $10–$60 | ~0.5–1.5 hrs |
This code only exists on V12s, where injector access often means removing intake plumbing and where parts carry luxury-brand pricing — real-world totals can exceed these ranges, which reflect common gasoline injectors. Diesel and exotic direct-injection injectors cost far more still.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0212 for my exact vehicle →
How to fix P0212
Advanced — usually a shop job unless you’re well equipped
- Locate the last cylinder on your V12 or W12
Cylinder 12 is the highest-numbered cylinder on V12 and W12 engines, and on most numbering schemes it ends up at the rear of the engine near the bulkhead, where heat builds and space is tightest. Confirm its exact position on a diagram for your engine before planning access.
- Record codes, freeze frame, and misfire data
Save every stored code and the freeze frame before clearing anything, including P0312 and any codes for other cylinders on that bank. Losing one of twelve cylinders can feel like almost nothing at idle, so the data captured now is what proves the fault and shows whether it is constant or intermittent.
- Check the cylinder 12 plug and terminals
Test the latch gently — on older engines these connectors can be very brittle — and look for corrosion, a backed-out terminal, or oil in the plug. Clean with contact cleaner and confirm it seats with a click; if the latch breaks, replace the connector rather than tying it in place.
- Measure the circuit before buying an injector
On port-injected engines, measure the cylinder 12 injector's resistance at its pins and compare it with others on the same bank, then check the control wire's continuity to the engine computer with a wiring diagram. On direct-injected engines, skip probing the live circuit and follow the service manual's injector tests.
- Replace parts only once the tests agree
A failed winding means a new injector, often requiring intake or cover removal at the back of the engine and new seals. The engine computer comes under suspicion only when wiring and injector both pass, and on these cars module replacement needs programming tools most home garages lack.
DIY or shop? Reading codes, checking the cylinder 12 connector where it can be reached, and taking resistance readings on a port-injected engine are fair game for a skilled owner. Anything that requires removing the intake, coil packs, or covers at the back of a twelve-cylinder engine is specialist work, as is all direct-injection service and any engine-computer replacement. Collect the data, fix what's visible, and let a platform specialist handle the rest.
Tools for the DIY steps: Scan tool that saves freeze frame · Digital multimeter · Electrical contact cleaner · Inspection mirror and flashlight · Wiring diagram
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0212.
Start a case with P0212 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 P0212?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0212: common questions
Can I keep driving my V12 with P0212?
A code alone can't settle that. The engine may still feel strong — that's the danger. The misfiring cylinder is loading the catalytic converter with raw fuel, and converter failure on a twelve-cylinder car is a dramatically bigger bill than an injector circuit repair. Get it fixed promptly, and stop driving if the light flashes.
Where is cylinder 12?
It's the last cylinder in the firing count, but which physical position that is depends on the manufacturer's numbering — V12 makers number their banks differently. Consult the cylinder-layout diagram for your specific engine before removing anything.
What's the most likely cause of P0212?
Connector and wiring problems lead the list — corrosion, a half-seated plug, or a wire chafed along the long harness runs a V12 requires. A failed injector winding is next. The engine computer's driver is a genuine but rare cause, so rule out everything else first.
Would swapping injectors help before I buy one?
You can — exchange the cylinder 12 injector with a neighbor and clear the codes. If the circuit code moves with the injector, buy the injector. If P0212 stays put, the money belongs in wiring diagnosis instead. On a V12, confirming before purchasing is especially worthwhile given parts prices.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0212 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 P0212 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.