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DTC codes / P02xx · Fuel and air metering (injector circuits) / P0212

P0212Injector Circuit/Open - Cylinder 12

P0212 is a generic OBD-II code indicating that the powertrain control module (PCM) has detected an open circuit or excessive resistance in the fuel injector circuit for cylinder 12. The PCM commands the injector on and monitors the electrical feedback; when the expected current does not flow, it flags the circuit as open and stores this code.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms besides the warning light
  • Rough idle or misfire that may be more pronounced when the engine is cold
  • Noticeable loss of power and reduced fuel economy due to a dead cylinder
  • Engine vibration or shaking, especially under acceleration or load
  • In some cases, a rich or lean fuel smell from the exhaust if the injector is stuck open or closed

Common causes, most likely first

  1. Failed fuel injector with an open internal coil winding
  2. Damaged or disconnected electrical connector at the injector
  3. Broken, chafed, or corroded wiring in the injector circuit between the PCM and the injector
  4. Open circuit in the shared power or ground circuit feeding the injector
  5. Faulty powertrain control module (PCM) driver for that injector (rare but possible)
  6. Corrosion or poor terminal tension at the PCM connector

How to diagnose and fix it

  1. Perform a visual inspection of the cylinder 12 injector connector and wiring for damage, corrosion, or looseness
  2. Use a noid light or injector pulse tester to confirm whether the PCM is commanding the injector and whether the circuit is complete
  3. Measure the resistance of the injector with a multimeter and compare it to the manufacturer's specification; an open winding confirms a failed injector
  4. Check for continuity and voltage drop across the injector circuit from the PCM to the injector, repairing any open or high-resistance wiring
  5. Inspect and clean the PCM connector terminals for cylinder 12 injector control, looking for corrosion or backed-out pins
  6. If the circuit and injector test good, substitute a known-good injector or use a lab scope to verify the PCM driver signal before condemning the PCM
  7. Clear the code and perform a road test to confirm the repair and ensure the code does not return

When the injector is not the culprit

  • A loose or corroded connector at the injector is a far more common cause of P0212 than a failed injector itself, so always inspect the plug before replacing parts.
  • The shared power feed or ground for the injector bank can open and set this code on cylinder 12 even though the injector and its individual signal wire test fine.
  • On engines with cylinder deactivation or multiple banks, a P0212 may be accompanied by codes for other cylinders on the same circuit, pointing to a common wiring fault rather than a single injector.
  • A noid light that does not blink does not automatically mean a bad PCM; verify power and ground at the injector connector first, because a blown fuse or open ground will mimic a failed driver.
  • After any injector replacement, check the fuel injector O-rings and seals for leaks or vacuum leaks that can cause a misfire unrelated to the electrical circuit.

Can I keep driving with P0212?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because the dead cylinder can overheat the catalytic converter and cause further damage. If the engine is running very rough or flashing the check engine light, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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