P0212

Injector Circuit Malfunction - Cylinder 12

P0212 is a generic OBD-II powertrain diagnostic trouble code: Injector Circuit Malfunction - Cylinder 12. 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.

Code
P0212
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0212 means

P0212 is an OBD-II code indicating the PCM has detected an electrical malfunction in the fuel injector drive circuit for cylinder 12. The PCM driver transistor for cylinder 12 commands the injector by pulling the ground circuit low; if the expected voltage transition is absent, inverted, or out of range—due to an open coil winding, a wiring fault, or a failed driver stage—the module stores P0212 and turns on the MIL. This is a circuit/electrical fault, distinct from P0312 (cylinder 12 combustion misfire), which is set based on crankshaft acceleration sensing and can stem from ignition or compression failures independent of the injector circuit.

Cylinder 12 is present only on V12 engines, making P0212 one of the rarer injector circuit codes in the OBD-II spectrum. Affected platforms include BMW N73 (E65/E66 760i/Li), BMW N74 (F01/F02/F03/G11 V12), BMW S70/2 (McLaren F1), Ferrari and Lamborghini V12 (F12/812, Aventador), Audi/VW W12 (A8 L 6.0, Bentley Continental GT), Mercedes-Benz M120/M137 V12 (S600, SL600, CL600), and Rolls-Royce and Bentley models sharing these architectures. Access to the cylinder 12 injector and its wiring in these tightly packaged engine bays often requires significant disassembly.

An inoperative cylinder 12 causes the engine to run on eleven cylinders, producing a noticeable misfire, vibration, and power deficit. On turbocharged V12 platforms, the thermal and pressure imbalance between cylinder banks can also stress turbocharger bearings and affect the exhaust aftertreatment system if unburned fuel is intermittently present in the exhaust stream.

Common causes

Most-frequently reported root causes when P0212 is logged.

  • 1
    Failed fuel injector coil on cylinder 12 (open or internally shorted winding).
  • 2
    Open circuit, broken wire, or damaged insulation in the cylinder 12 injector harness.
  • 3
    Corroded, loose, or improperly seated electrical connector at the cylinder 12 injector.
  • 4
    Short to ground or short to battery voltage on the injector signal or ground wire.
  • 5
    Failed PCM injector driver transistor for the cylinder 12 channel.
  • 6
    Heat-damaged wiring routed near the rear exhaust manifold or turbocharger on cylinder bank 2.
  • 7
    Water or oil contamination inside the injector connector causing intermittent signal loss.

Symptoms drivers notice

MIL illuminated, often with P0312 (cylinder 12 misfire) stored concurrently.
Perceptible engine rough idle and vibration from an inoperative cylinder 12.
Reduced power output and sluggish response, most apparent under load in V12-powered vehicles.
Elevated fuel consumption and worsened exhaust emissions due to incomplete combustion.
Possible intermittent exhaust backfires or fuel smell if the circuit fault is intermittent and unburned mixture occasionally reaches the exhaust.

How to diagnose P0212

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and freeze-frame data; confirm P0312 cylinder 12 misfire presence and note load/temperature conditions at fault occurrence.
  2. 2
    Visually inspect the cylinder 12 injector connector and harness routing for corrosion, heat damage, cracked insulation, or loose retaining clips—pay attention to the rear of the engine where cylinder 12 is often most recessed.
  3. 3
    Disconnect the cylinder 12 injector connector and measure injector coil resistance with a multimeter; compare to OEM specification (typically 12–17 Ω for high-impedance port-injection units; 1–3 Ω for GDI peak-and-hold injectors).
  4. 4
    Reconnect the injector and use a noid light or oscilloscope at the connector while cranking to verify the PCM is generating a drive pulse for cylinder 12.
  5. 5
    If no drive pulse is present, perform continuity and short-circuit tests on the injector signal wire from the connector back to the PCM injector driver pin.
  6. 6
    Swap the cylinder 12 injector with a confirmed-good injector from an adjacent cylinder; if the P0212 code and symptom migrate to the swapped position, the injector coil has failed.
  7. 7
    If injector and wiring tests are within spec, consult the OEM wiring diagram, test the PCM driver pin output directly, and follow the manufacturer's ECU replacement or recoding procedure.

Related powertrain codes

Frequently asked questions

Which vehicles can set P0212?

Only V12-engined vehicles: BMW 760i/Li (N73/N74 engine), McLaren F1 (BMW S70/2), Ferrari 812 Superfast and related V12 models, Lamborghini Aventador (6.5 L V12), Audi A8 L 6.0 W12 and Bentley Continental GT/Flying Spur W12, Mercedes-Benz S600/CL600/SL600 (M120/M137), and Rolls-Royce/Bentley models with V12 powertrains.

Can P0212 be caused by an ECU fault rather than the injector or wiring?

Yes, though it is uncommon. If the injector resistance and all wiring continuity tests are normal but the noid light shows no pulse at the cylinder 12 connector, the PCM injector driver transistor for that channel may have failed internally. This is more likely on high-mileage ECUs or those that have experienced a voltage spike or water ingress.

Is P0212 more difficult to diagnose than P0201 on a common four-cylinder?

Diagnostically the procedure is the same—check resistance, check pulse, check wiring. Practically it is more challenging because cylinder 12 is often at the rear of a densely packaged V12 bay, requiring removal of intake plenums, covers, or other ancillary components just to access the injector and connector. Labour time therefore tends to be substantially higher than for a front-mounted cylinder on a simpler engine.

If I have both P0212 and P0312 stored, which do I fix first?

Address P0212 first. The injector circuit fault (P0212) is the likely root cause preventing fuel delivery to cylinder 12, which in turn triggers the misfire event logged as P0312. Once the injector circuit is repaired and verified, clear both codes and confirm that P0312 does not return during a normal drive cycle.

Disabling P0212 in software

RaceTune can permanently disable P0212 — 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.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

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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