Diesel Trouble Codes

P0201 — Injector Circuit/Open - Cylinder 1 (6.7 Cummins (SCR / DEF))

P0201 on 6.7L Cummins SCR/DEF 2013–present means the ECM has detected an electrical fault in the fuel injector circuit for cylinder 1.

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 / connector, or chafed/damaged harness to the injector driver — Inspect the injector 1 electrical connector and harness for corrosion, loose terminals, or chafing. Check continuity and isolation of the injector control circuit from ECM to injector. This is the most common electrical cause for P0201 on common-rail solenoid injectors.1
  2. Faulty injector 1 solenoid / internal open coil — A failed injector solenoid presents as an open circuit to the ECM. Verify injector coil resistance per service data and compare to other cylinders. Injectors are common-rail solenoid type on this platform.1
  3. ECM injector driver fault for cylinder 1 — If wiring and injector test good, the ECM internal driver for cylinder 1 may be faulty. Confirm by swapping injector electrical connections with another cylinder (if supported) and observing code movement, then evaluate ECM. Generic definition is ECM detected electrical fault in injector circuit.1
  4. Poor ground or power supply to ECM/injector driver circuit — Voltage drop or intermittent ground can trigger circuit/open detection. Check ECM power/ground circuits and related fuses/relays before condemning ECM. Electrical fault detection is ECM-based.1

How to diagnose

  1. Verify code and freeze frame; confirm P0201 is active and note engine conditions.
  2. Visually inspect injector 1 connector, harness routing, and ECM connectors for damage, corrosion, or oil intrusion.
  3. Perform pinpoint electrical tests of injector 1 circuit: continuity, resistance, isolation to ground/power per service information.
  4. Compare injector 1 solenoid resistance to cylinders 2-6; solenoid injectors used on this platform.
  5. Inspect related ECM power/ground circuits and fuses.
  6. If wiring and injector pass, evaluate ECM injector driver per manufacturer diagnostics; do not perform step-by-step repair of high-pressure fuel lines.

Parts and tools you may need

Rough cost and difficulty

Electrical diagnosis is labor-intensive; parts cost varies by whether repair is wiring repair, injector replacement, or ECM. High-pressure fuel system work is safety-critical; refer to professional service.

When to see a pro

If diagnosis points to ECM driver failure or requires high-pressure fuel system access, have a qualified diesel technician perform testing and repairs. Do not perform step-by-step repair of safety-critical high-pressure fuel components.

Sources

  1. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎