P0294

Cylinder 12 Injector Circuit Low

P0294 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 12 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.

Code
P0294
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0294 means

P0294 is triggered when the ECM detects a voltage or current level at the cylinder 12 fuel injector circuit that falls below the manufacturer's minimum threshold. The ECM supplies a precisely timed voltage pulse to the injector solenoid; if the signal returning from the cylinder 12 injector circuit reads consistently low — indicating high resistance, an open circuit, or loss of ground — P0294 is stored and the MIL is illuminated. Cylinder 12 can only exist in a true 12-cylinder engine: BMW N73/N74 V12, Mercedes-Benz M120/M275/M279 V12, Ferrari/Lamborghini V12 naturally-aspirated engines, Aston Martin AM11 V12, and the Volkswagen/Audi/Bentley W12. On Cummins ISX engines using a dual-injector-per-cylinder strategy, a secondary injector circuit fault on the last cylinder can also produce this code.

The most common cause is a corroded or loose injector connector — the cylinder 12 position sits at the rearmost end of the engine, often near the firewall, where heat soak and restricted access combine to accelerate connector degradation. An open-circuit injector coil, a wiring break in the harness, or a blown fuse in the injector power supply circuit are also frequent culprits. ECM driver failure is rare but must be tested if all passive components measure correctly.

With cylinder 12 not receiving fuel, raw hydrocarbons enter the exhaust and can rapidly overheat and damage the catalytic converter. The engine also runs on 11 cylinders, causing vibration and power loss disproportionate to the displacement. Prompt inspection of the connector and wiring is the correct first step before ordering replacement parts.

Common causes

Most-frequently reported root causes when P0294 is logged.

  • 1
    Corroded, loose, or moisture-contaminated connector on the cylinder 12 injector harness.
  • 2
    Open circuit or wire break in the harness between the ECM and the cylinder 12 injector.
  • 3
    Failed fuel injector with an internally open solenoid coil (infinite or very high resistance).
  • 4
    Blown fuse or failed relay in the fuel injection power supply circuit.
  • 5
    Short to ground in the injector signal wire reducing measured voltage below threshold.
  • 6
    Poor ECM or injector chassis ground connection elevating circuit impedance.
  • 7
    ECM injector driver transistor failure for cylinder 12 unable to deliver the correct activation signal.

Symptoms drivers notice

Check Engine Light on, commonly accompanied by a cylinder 12 misfire code.
Rough idle and engine vibration from the non-contributing cylinder 12.
Significant loss of power and torque, most noticeable on acceleration.
Worsening fuel economy as the ECM attempts to compensate on remaining cylinders.
Increased exhaust emissions and possible raw-fuel smell from the exhaust.
Potential engine stalling in severe cases where the imbalance disrupts idle stability.

How to diagnose P0294

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored DTCs and freeze-frame data; note companion misfire codes and whether P0295 (cylinder 12 injector circuit high) or contribution codes are also present.
  2. 2
    Inspect the cylinder 12 injector connector for corrosion, pushed-out pins, or moisture ingress — clean terminals or repair the connector before further testing.
  3. 3
    Check all fuel-injection fuses and relays; replace any blown fuse and verify the circuit does not immediately blow a replacement (indicating a hard short).
  4. 4
    Unplug the injector connector and measure coil resistance with a multimeter; compare to OEM specification and replace the injector if resistance is open or out of range.
  5. 5
    Swap the cylinder 12 injector with an adjacent cylinder's injector and re-scan; if the low-circuit code follows the injector, the injector is confirmed faulty.
  6. 6
    Perform a continuity and insulation test on the harness wire from the ECM pin to the injector connector; repair any open or grounded section found.
  7. 7
    If wiring and injector test normal, use a scan tool to command the injector and measure ECM driver output voltage to confirm or rule out an ECM fault before replacement.

Related powertrain codes

Frequently asked questions

Which vehicles can set P0294?

Only true 12-cylinder engines: BMW 7 Series/Rolls-Royce with N73 or N74 V12, Mercedes-Benz S600/SL65/CL65/Maybach with M120/M275/M279 V12, Ferrari V12 (812, F12, 599), Lamborghini Aventador V12, Aston Martin with AM11 V12, Bentley and Audi with the 6.0 W12, and select Cummins ISX diesel configurations.

Why is cylinder 12 particularly prone to connector corrosion?

Cylinder 12 is the last cylinder in the firing order and physically sits at the rear of the engine closest to the firewall. This location makes it the hottest-running connector position during heat soak after engine shutdown, and it is the hardest to access for routine visual inspection, so connector degradation goes unnoticed longer than on front cylinders.

Can a blown fuse cause P0294 without the injector or wiring being damaged?

Yes. Some V12 and W12 engines protect each injector bank with individual fuses. A blown fuse cuts power to the entire bank or to a sub-group, which can single out cylinder 12 if the fuse layout maps to the rear cylinders. Always check fuses before condemning the injector or harness.

How dangerous is it to drive with P0294 active?

Driving should be minimised. Cylinder 12 misfiring continuously sends raw fuel into the exhaust, which can destroy the catalytic converter in as little as a few hundred miles. Catalytic converter replacement on V12 platforms is significantly more expensive than the injector or harness repair that caused the original fault.

Disabling P0294 in software

RaceTune can permanently disable P0294 — 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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