P0212 is a generic OBD-II powertrain code that means Injector Circuit/Open Cylinder 12. The ECM/PCM has detected an electrical fault in the fuel injector circuit associated with Cylinder 12.
P0212 does not automatically mean the injector is bad. The cause can be the injector, connector, wiring, power supply, fuse, control circuit, or, less commonly, the ECM/PCM injector driver.
P0212 Code Definition
- Code: P0212
- System: Fuel and engine control
- Type: Generic OBD-II Powertrain DTC
- Definition: Injector Circuit/Open Cylinder 12
- Main circuit: Cylinder 12 fuel injector circuit
What Does P0212 Mean?
The ECM/PCM monitors the electrical operation of the Cylinder 12 injector circuit. When the module detects an open circuit or another abnormal electrical condition, it can store P0212.
An open circuit may result from a broken wire, disconnected connector, damaged terminal, excessive resistance, loss of injector power, an internally defective injector, or a problem with the ECM/PCM control circuit.
Important: Does the Engine Have Cylinder 12?
Cylinder 12 is not found on most passenger vehicles. P0212 is therefore uncommon and is relevant only to engine configurations that actually contain a Cylinder 12.
Before replacing an injector, confirm the exact engine configuration, cylinder numbering, and manufacturer-specific code information. If the vehicle does not have twelve cylinders, verify the scan-tool information and vehicle application before continuing with the diagnosis.
Symptoms of P0212
- Check Engine Light.
- Engine misfire.
- Rough idle.
- Engine vibration.
- Hesitation during acceleration.
- Reduced engine power.
- Poor fuel economy.
- Hard starting.
- Engine stalling in severe cases.
- Flashing Check Engine Light if a severe misfire occurs.
Common Causes of P0212
- Failed Cylinder 12 fuel injector.
- Open injector circuit.
- Broken injector control wire.
- Damaged injector connector.
- Loose or pushed-out electrical terminal.
- Corrosion inside the connector.
- High resistance in the injector circuit.
- Loss of injector power supply.
- Blown injector or engine-control fuse, where applicable.
- Damaged engine wiring harness.
- Intermittent wiring caused by vibration or heat.
- Previous incorrect wiring repair.
- ECM/PCM injector-driver fault.
How to Diagnose P0212
1. Scan for Additional Codes
Use a professional scan tool to confirm P0212 and check for additional injector, misfire, fuel-system, power-supply, or communication codes.
If several injector codes appear simultaneously, investigate a shared power supply, fuse, relay, or harness before condemning individual injectors.
2. Confirm Cylinder 12
Verify that the engine actually has Cylinder 12 and identify its location using manufacturer service information. Cylinder numbering varies between engine designs.
3. Inspect the Injector and Connector
Inspect the Cylinder 12 injector connector for corrosion, water intrusion, damaged terminals, loose connections, broken locking mechanisms, and damaged wiring.
Pay particular attention to wiring close to the engine where heat, vibration, oil, and mechanical movement can damage the harness.
4. Check the Fuse Box
Inspect the applicable injector or engine-control fuse. Depending on the vehicle, the fuse may be identified by an abbreviation such as INJ, EFI, ECM, PCM, ECU, ENG, or FUEL.
The fuse number and location are vehicle-specific. Always use the correct fuse-box diagram rather than assuming that the same fuse designation applies to every vehicle.
If the fuse is blown, find the reason for the excessive current draw before installing another fuse.
5. Check Injector Power
Using the correct wiring diagram, identify the injector power circuit and verify that the injector receives the expected supply under the manufacturer's test conditions.
Many systems provide a common power supply to multiple injectors while the ECM/PCM controls individual injectors through the control side. The actual circuit design varies by vehicle.
6. Test Injector Resistance
Where applicable, measure the resistance of the Cylinder 12 injector and compare it with the manufacturer's specification for that exact injector.
Do not use one generic resistance value for all fuel injectors. Injector technology and specifications vary considerably.
7. Check the Complete Wiring Circuit
Test the circuit between the injector and ECM/PCM for continuity, excessive resistance, shorts, damaged insulation, and intermittent connections.
A voltage-drop test can be particularly useful when a circuit appears normal with a basic continuity test but fails under load.
8. Test the ECM/PCM Driver
If the injector, connector, fuse, power supply, and wiring all test correctly, follow the manufacturer's procedure for testing the ECM/PCM injector driver.
Do not replace the ECM/PCM simply because P0212 is present.
P0212 Electrical Signal Flow
↓
Fuse / Power Distribution
↓
Cylinder 12 Injector
↓
Injector Control Circuit
↓
ECM / PCM Driver
↓
Fuel Delivery
↓
Cylinder 12 Combustion
P0212 Live Data Diagnosis
With an advanced scan tool, monitor available parameters such as:
- Engine RPM.
- Engine load.
- Short-term and long-term fuel trims.
- Cylinder-specific misfire counters.
- Injector-related parameters.
- Commanded fuel information.
- Oxygen/Air-Fuel sensor data.
- Manufacturer-specific fuel-system parameters.
If cylinder-specific misfire data is available, compare Cylinder 12 with the other cylinders.
Fuel trims can provide supporting evidence of a fuel-delivery problem, but fuel-trim values alone cannot prove that the Cylinder 12 injector is defective.
An intermittent open circuit may also disappear while monitoring live data, so electrical testing should be performed alongside scan-tool analysis.
P0212 Oscilloscope Testing
An oscilloscope can provide a more detailed view of the injector control signal. The exact waveform depends on the injector design and ECM/PCM driver strategy.
Simplified Injector Control
Injector Power
│
▼
Injector
│
▼
ECM / PCM Driver
│
▼
Control Pulse
┌──────┐ ┌──────┐
───────┘ └───────┘ └──────
ON ON
For professional diagnosis, compare the Cylinder 12 signal with a known-good injector or the manufacturer's specified waveform. A generic waveform should not be treated as a universal pass/fail specification.
Can a Bad Injector Cause P0212?
Yes. An internally open or electrically abnormal injector can trigger P0212.
However, replacing the injector immediately is not recommended. The connector, fuse, power supply, wiring, and ECM/PCM control circuit should be tested first.
Can a Fuse Cause P0212?
Yes. If the applicable injector power circuit is protected by a fuse, a blown fuse or poor fuse-box connection can interrupt injector operation.
If several injector codes appear together, investigate the common power supply, fuse, relay, and wiring before replacing multiple injectors.
Is P0212 Serious?
P0212 can be serious if it causes Cylinder 12 to stop receiving the correct amount of fuel and produces a significant misfire.
A severe misfire can cause poor drivability, increased emissions, loss of power, and possible damage to emission-control components depending on the engine and operating conditions.
Can I Drive With P0212?
Limited driving may be possible if the engine is running normally, but the problem should be diagnosed promptly.
If the Check Engine Light is flashing, the engine is shaking badly, power is substantially reduced, or a severe misfire is present, avoid continued driving until the fault is diagnosed.
P0212 Repair Cost
- Electrical diagnosis: about $50–$150+.
- Injector connector repair: about $50–$200+.
- Injector wiring repair: about $50–$250+.
- Fuel injector replacement: about $100–$500+ depending on the engine and injector.
- Fuse or power-circuit repair: about $50–$200+ depending on the cause.
- ECM/PCM diagnosis or repair: potentially considerably more.
These are general estimates. Actual cost depends on the vehicle, engine, parts, labor rates, accessibility, and underlying fault.
Common Repair Mistakes
- Replacing the injector without testing the circuit.
- Failing to verify that Cylinder 12 actually exists.
- Ignoring the injector connector.
- Ignoring the fuse box and injector power supply.
- Using an incorrect injector resistance specification.
- Failing to perform voltage-drop testing.
- Ignoring intermittent wiring faults.
- Using the wrong cylinder numbering.
- Replacing the ECM/PCM before proving that its driver is faulty.
- Replacing a blown fuse repeatedly without finding the cause.
Related Codes
- P0200 – Injector Circuit Malfunction.
- P0201 – Injector Circuit/Open Cylinder 1.
- P0202 – Injector Circuit/Open Cylinder 2.
- P0203 – Injector Circuit/Open Cylinder 3.
- P0204 – Injector Circuit/Open Cylinder 4.
- P0205 – Injector Circuit/Open Cylinder 5.
- P0206 – Injector Circuit/Open Cylinder 6.
- P0207 – Injector Circuit/Open Cylinder 7.
- P0208 – Injector Circuit/Open Cylinder 8.
- P0209 – Injector Circuit/Open Cylinder 9.
- P0210 – Injector Circuit/Open Cylinder 10.
- P0211 – Injector Circuit/Open Cylinder 11.
- P0312 – Cylinder 12 Misfire Detected.
FAQ About P0212
What does P0212 mean?
P0212 means Injector Circuit/Open Cylinder 12. It indicates an electrical problem detected in the Cylinder 12 fuel-injector circuit on an applicable engine.
Why is P0212 uncommon?
Most passenger vehicles do not use a twelve-cylinder engine, so Cylinder 12 injector faults are much less common than injector faults on smaller engines.
How do I fix P0212?
Confirm the engine configuration, inspect the Cylinder 12 injector and connector, check the applicable fuse and power supply, test the wiring and control circuit, and verify the ECM/PCM driver before replacing components.
Can wiring cause P0212?
Yes. A broken wire, high-resistance connection, damaged terminal, corrosion, or intermittent harness fault can interrupt the Cylinder 12 injector circuit.
Can P0212 cause a misfire?
Yes. If Cylinder 12 is not receiving the correct injector command or fuel delivery, the cylinder can misfire and cause rough running, vibration, hesitation, and reduced power.
Does P0212 mean the ECM is bad?
No. An ECM/PCM driver fault is possible, but it should normally be considered only after the injector, connector, fuse, power supply, and wiring have been tested.
What is the difference between P0212 and P0312?
P0212 identifies an injector-circuit electrical problem involving Cylinder 12, while P0312 indicates a detected misfire on Cylinder 12. The two codes can occur together but describe different conditions.
What if my vehicle does not have twelve cylinders?
If the engine does not contain Cylinder 12, verify the scan-tool data, vehicle identification, module configuration, and applicable DTC definition before performing any injector repair.
Final Takeaway
P0212 is a Cylinder 12 injector circuit/open fault. It should not be interpreted as proof that the fuel injector itself has failed.
The correct diagnostic sequence is to verify the engine configuration, inspect the injector, connector, fuse box, power supply, wiring, control signal, and ECM/PCM driver before replacing expensive components.
Always use the vehicle-specific wiring diagram, fuse-box information, injector specifications, cylinder numbering, and manufacturer diagnostic procedure.