Diesel Trouble Codes

P0201 — Injector Circuit/Open - Cylinder 1 (L5P Duramax)

Diagnostic reference for P0201 on L5P Duramax (2017–present).

Updated September 2, 2026

What it means

The engine control module has detected an electrical fault in the fuel injector circuit for cylinder number one.1

Most likely causes

  1. Open or high resistance in injector 1 wiring harness or connector — Inspect harness for chafing, pin corrosion, or loose terminals at injector 1 and ECM. Check continuity and isolation to ground/power.1
  2. Failed injector 1 solenoid coil (open circuit) — Bosch common-rail solenoid injectors are externally mounted on L5P. An open coil triggers P0201–P0208.1
  3. ECM driver fault for injector 1 — Internal ECM injector driver failure can set circuit/open code. Verify with known-good harness and injector before condemning ECM.1
  4. Poor ground or power supply to injector bank — Shared power/ground issues can appear as a single-cylinder circuit fault. Verify injector supply voltage and ground integrity.1

How to diagnose

  1. Verify code and freeze frame; confirm P0201 is current and not historical.
  2. Visually inspect injector 1 connector and harness for damage, oil intrusion, or corrosion.
  3. Measure injector 1 solenoid resistance per service spec and compare to other cylinders.
  4. Perform pin-to-pin continuity from injector 1 connector to ECM harness connector; check for opens/shorts to ground or battery.
  5. Command injector circuit test with scan tool if available; observe ECM driver feedback.
  6. Swap injector 1 electrical connector with adjacent cylinder to see if code follows wiring.
  7. If wiring and injector test good, evaluate ECM driver output.

Parts and tools you may need

Rough cost and difficulty

Electrical diagnosis labor varies; injector replacement requires high-pressure fuel system depressurization and proper priming per L5P procedures.

When to see a pro

If ECM driver is suspected or high-pressure fuel system opening is required, have a qualified diesel technician perform diagnosis and repair. Do not service high-pressure fuel components without proper training and safety equipment.

Sources

  1. Curated DTC seed — L5P Duramax (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎