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DTC codes / Volkswagen codes / P1216

P1216 · VolkswagenCylinder 4 Fuel Injector Circuit Short To B+

P1216 on a Volkswagen means the engine control module (ECM) has detected a short to battery voltage on the electrical circuit that powers cylinder 4's fuel injector. The ECM monitors the injector driver circuit and sees voltage present when the injector should be off, indicating a wiring fault or a failed injector rather than a normal open circuit.

SystemPowertrain
Code typeVolkswagen specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire felt as shaking, especially when the engine is cold
  • Reduced engine power or limp mode under acceleration
  • Increased fuel consumption due to incorrect fuel delivery
  • Possible strong fuel odor from the exhaust if the injector is stuck open
  • In rare cases, the engine may crank but not start if the injector driver is disabled

Common causes, most likely first

  1. Faulty cylinder 4 fuel injector with an internal short to its power feed
  2. Chafed or damaged injector harness wiring shorting to a battery-positive wire
  3. Corroded or loose electrical connector at the cylinder 4 injector
  4. Short inside the engine wiring harness where it rubs against the engine block or chassis
  5. Failed engine control module (ECM) injector driver circuit (less common)
  6. Aftermarket alarm or remote starter wiring tapped into the injector circuit incorrectly

How to diagnose and fix it

  1. Scan all modules for fault codes and record freeze-frame data to confirm P1216 is current and not history
  2. Visually inspect the cylinder 4 injector connector and harness for chafing, corrosion, or loose pins
  3. Measure resistance across the cylinder 4 injector terminals and compare with the other three injectors
  4. With the key on and engine off, check for battery voltage on the injector control wire with the connector unplugged; voltage indicates a short to B+
  5. Disconnect the ECM connector and check for continuity between the injector control wire and battery positive; repair any shorted section of harness
  6. Swap the cylinder 4 injector with a known-good injector from another cylinder and see if the code moves
  7. If wiring and injector test good, test the ECM driver circuit or substitute a known-good ECM to confirm internal failure

Why a short to B+ is not always the injector

  • A short to battery voltage on an injector circuit often originates in the harness where it passes near the exhaust manifold or sharp metal edges, not inside the injector itself.
  • Many technicians replace the injector first and find the code returns because the real fault is a rubbed-through wire hidden inside the loom.
  • P1216 can be set intermittently by water intrusion into the injector connector after engine washing or heavy rain, leaving no permanent damage.
  • A failed ECM driver is rare but possible; always rule out wiring and injector resistance before condemning the module.
  • This code does not always mean the injector is stuck open; a short to B+ can hold the injector off entirely, causing a dead cylinder rather than a rich condition.

Can I keep driving with P1216?

You can drive short distances to a repair shop, but avoid heavy acceleration and long trips because a misfiring cylinder can overheat the catalytic converter and waste fuel. If the engine runs very rough or smells strongly of fuel, stop driving and have the vehicle 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 Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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