P0201 — Injector Circuit/Open - Cylinder 1 (5.9 Cummins Common Rail)

Diagnostic reference for P0201 on 5.9 Cummins Common Rail 2003-2007. Covers meaning, most likely causes, quick checks, and safe diagnostic steps without…

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. On this platform the 5.9L Cummins Common Rail 2003-2007 ISB uses Bosch common-rail solenoid injectors; electrical faults show as P0201-P0206; contribution/balance issues show as P0263-family.¹²

Most likely causes

1. Open or high resistance in injector 1 wiring/harness or connector — Chafing, heat damage, or corrosion at the injector 1 connector or engine harness can create an open circuit detected by the ECM.¹²
2. Faulty injector 1 solenoid/coil — Internal open in the Bosch common-rail solenoid injector for cylinder 1 will set an electrical circuit fault.¹²
3. ECM driver fault for injector 1 — Internal ECM injector driver failure or poor ECM connector/pin contact can appear as a circuit/open for cylinder 1.¹
4. Poor ground or power supply to injector rail — Shared power/ground issues affecting the injector group can trigger a single-cylinder circuit code.¹

How to diagnose

1. Verify code and freeze frame; confirm P0201 is present and not accompanied by rail pressure or contribution codes.
2. Inspect injector 1 connector and engine harness for chafing, heat damage, oil contamination, and secure lock. Compare visually to other injectors.
3. Check ECM and injector harness connectors for corrosion, bent pins, and proper seating.
4. Perform electrical tests at the injector connector for continuity and isolation per service information; compare injector 1 readings to adjacent cylinders.
5. Inspect related grounds and power feeds for the injector group.
6. If electrical tests pass, evaluate injector 1 solenoid resistance/signature against spec and compare to other cylinders.
7. Review recent work, heat exposure, or fluid leaks that could affect the injector 1 circuit.
8. Clear codes and monitor for reoccurrence under normal driving conditions.

Parts and tools you may need

• Digital multimeter
• Scan tool with live data and code read/clear
• Inspection light
• Contact cleaner
• Dielectric grease

Rough cost and difficulty

Electrical diagnosis is labor-intensive. Parts range from wiring repair to injector replacement; ECM issues are higher cost. Costs vary by region and labor rates.

When to see a pro

If wiring tests are inconclusive, injector electrical values are out of spec, or ECM driver is suspected, have a qualified diesel technician perform pinpoint electrical tests and ECM evaluation. Do not attempt high-pressure fuel system service without proper training and tools.

Sources