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DTC codes / Volkswagen codes / P1220

P1220 · VolkswagenCylinder 8 Fuel Injector Circuit Short To B+

P1220 on a Volkswagen indicates that the engine control module (ECM) has detected a short to battery voltage on the fuel injector circuit for cylinder 8. The ECM monitors the injector driver circuit and expects a specific voltage pattern when the injector is commanded on and off; a short to B+ means the control wire is seeing constant battery voltage, which the ECM interprets as a fault.

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

Symptoms you may notice

  • Illuminated check engine light (malfunction indicator lamp)
  • Rough idle or misfire, especially noticeable at idle or low speeds
  • Engine hesitation or stumble during acceleration
  • Reduced engine power or limp mode in some cases
  • Often no symptoms besides the warning light, because the ECM may disable the injector to protect the circuit

Common causes, most likely first

  1. Chafed or damaged injector wiring harness shorting to a power wire or the battery positive terminal
  2. Faulty fuel injector for cylinder 8 with an internal short to the coil's power feed
  3. Corroded or loose electrical connector at the cylinder 8 injector
  4. Damaged ECM driver circuit for the cylinder 8 injector (less common)
  5. Aftermarket accessories or improper wiring repairs that route power near the injector circuit
  6. Water intrusion or debris in the injector connector causing a conductive path to B+

How to diagnose and fix it

  1. Scan all modules for stored codes and verify P1220 is current; clear codes and test-drive to see if it returns.
  2. Visually inspect the cylinder 8 injector connector and wiring for chafing, corrosion, or signs of shorting to nearby power wires.
  3. Disconnect the cylinder 8 injector and measure resistance across its terminals; compare with a known-good injector (typically 12–16 ohms).
  4. With the injector disconnected and ignition on, measure voltage on the injector control wire (ECM side) to ground; it should not show battery voltage with the injector unplugged.
  5. Check for continuity between the injector control wire and battery positive or other power feeds; repair any short found in the harness.
  6. If wiring and injector test good, substitute a known-good injector or perform an injector balance test to rule out an internal injector short.
  7. If the fault persists after all external checks, test the ECM driver circuit with an oscilloscope or substitute a known-good ECM for diagnosis.

Don't overlook the injector harness routing

  • A common cause on Volkswagen engines is the injector harness rubbing against the engine cover or intake manifold, wearing through insulation and shorting to a power wire.
  • The ECM may set P1220 even if the injector itself is good, because the short can be intermittent and only appear when the engine is hot or vibrating.
  • A short to B+ on one injector circuit can cause the ECM to shut down the entire bank or enter limp mode, leading to multiple misfire codes that mask the root cause.
  • Aftermarket alarm or remote start installations often tap into injector wiring and can introduce a short to power if not properly fused or routed.
  • Resistance testing alone can miss an injector that shorts only when energized; an injector balance test or oscilloscope pattern is more reliable.

Can I keep driving with P1220?

It is not advisable to continue driving with this fault because a shorted injector circuit can cause misfiring, reduced power, and potential damage to the ECM or catalytic converter. If you must drive to a repair shop, keep the engine speed low and avoid heavy acceleration, and have the vehicle inspected as soon as possible.

Tools that help

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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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