P1205

Code

VOLKSWAGEN P — Powertrain

Cylinder 5 Fuel Injector Circuit Electrical Malfunction

Brand: VOLKSWAGEN

Type: P — Powertrain

Views: UK: 26 EN: 55 RU: 47

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Page language: EN

Causes

Open or shorted injector wiring (broken conductor, chafing, pinched cable)
Poor or corroded connector at the injector or wiring harness
Failed fuel injector (electrical short or open coil)
Faulty injector driver or power transistor in the engine control module (ECM)
Blown or corroded fuse or bad relay supplying injector circuit
Intermittent connection due to movement, heat, or contamination

Symptoms

Malfunction Indicator Lamp (MIL) illuminated with P1205 stored
Rough idle or rough running, especially under load
Single-cylinder misfire (cylinder 5) and related misfire codes (P0305)
Reduced engine power or limp-home mode in some vehicles
Hard starting or cranking but no start (if injector stuck open/shorted)
Decreased fuel economy and increased emissions

What to check

Read freeze frame and live data with a diagnostic scanner to confirm status and related codes (e.g., P0305)
Visual inspection of injector connector, wiring harness, and nearby heat sources for damage or corrosion
Check for loose or corroded battery, main fuse, or relay related to fuel injectors
Measure injector coil resistance at cylinder 5 and compare to manufacturer specification
Back-probe injector connector with oscilloscope or lab scope to view injector drive waveform
Wiggle test harness and connector while monitoring fault status to find intermittent faults

Signal parameters

Injector supply voltage: battery voltage (approx. 11–14.5 V with engine running) on the + terminal
Injector driver behavior: ECU typically grounds the injector pulse; back-probe low side should switch between ~0 V (on) and battery voltage (off)
Injector coil resistance: typical ranges - low-impedance injectors ≈ 2–4 Ω, high-impedance injectors ≈ 10–18 Ω — check vehicle/service manual for exact spec
Pulse width: varies with load and rpm; often 1–10 ms in normal operation (use scope or scan tool to measure)
No-load/idle pulses: regular, consistent pulses correlated to engine speed and injector multiplexing

Diagnostic algorithm

Retrieve and record freeze frame, pending codes, and live data. Note related misfire events, fuel trims, and injector enable status for cylinder 5.
Perform a visual inspection of the injector connector, wiring loom, and nearby components. Look for melted insulation, pinch points, corrosion, or rodent damage.
With ignition OFF, disconnect the injector connector at cylinder 5 and inspect for corrosion, bent pins, or moisture. Reconnect firmly.
Measure injector coil resistance at the injector pins (engine OFF). Compare to spec. If out of range, replace the injector.
Check supply fuse/relay and measure battery voltage at the injector supply pin with ignition ON. Confirm good ground continuity from injector low-side to ECU connector.
Back-probe the injector harness with an oscilloscope or lab scope while cranking/idle to confirm proper pulse waveform and switching between ~0 V and battery voltage.
If waveform shows constant open/short or no switching but other injector channels function correctly, inspect wiring back to the ECU for opens/shorts and perform continuity/resistance checks to the ECU connector.
Perform a wiggle/stress test on the harness and connectors while monitoring for intermittent faults or changes in waveform/MIL.
If wiring and connector are good and a replacement injector behaves the same, consider ECM driver fault. Verify with manufacturer diagnostic procedures before replacing the ECM.
After repairs, clear codes and perform a road test to verify the fault does not return and engine runs normally.

Likely causes

Damaged or corroded connector at cylinder 5 injector
Broken or shorted wire in harness near cylinder 5 (heat/abrasion common)
Failed injector (coil open or shorted)
ECM driver fault for injector channel 5 (less common)
Faulty ground or supply fuse/relay to the injector bank

Fault status

⚠️ Status

Cylinder 5 fuel injector circuit electrical malfunction detected — check injector, connector, wiring and ECU driver for open/short/intermittent fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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P1205 — Cylinder 5 Fuel Injector Circuit Electrical Malfunction