Diesel Trouble Codes

P0201 — Injector Circuit/Open - Cylinder 1 (6.7 Cummins (EGR + DPF, pre-SCR))

The ECM has detected an electrical fault in the fuel injector circuit for cylinder 1 on a 6.7L Cummins 2007.5–2012 (EGR+DPF, pre-SCR).

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 the injector harness or connector at cylinder 1 — Inspect the injector connector and engine harness for corrosion, oil intrusion, chafing, or loose terminals. Check continuity and isolation to ground/power per the wiring diagram.1
  2. Failed injector solenoid/electrical coil on cylinder 1 — A shorted or open injector coil will set a circuit fault. Compare injector resistance to spec and to other cylinders; a deviation indicates a bad injector.1
  3. ECM driver fault for cylinder 1 injector — If the wiring and injector test good, the ECM internal driver for cylinder 1 may be faulty. Verify power/ground and command signals at the ECM connector before condemning the module.1
  4. Chafed or shorted engine harness affecting injector circuits — The 6.7 Cummins uses a common-rail solenoid injector set with a single engine harness. Damage near the valve cover or bulkhead can cause an open/short on one cylinder.2
  5. Poor ECM power/ground or intermittent connection causing injector circuit codes — Low voltage or poor grounds can produce spurious injector circuit faults. Check battery, chassis, and ECM grounds and supply voltage under load.1

How to diagnose

  1. Verify code and freeze frame; clear and retest to confirm repeatability.
  2. Visually inspect cylinder 1 injector connector, harness routing, and valve cover area for oil, corrosion, or chafing.
  3. Measure injector solenoid resistance at the injector connector and compare to cylinders 2–6; note any open/short.
  4. Perform a pin-to-pin continuity and isolation test from ECM harness connector to injector connector for cylinder 1; check for shorts to ground or power.
  5. Inspect ECM connectors for moisture/corrosion and verify ECM power and ground circuits are within spec under load.
  6. If wiring and injector pass, scope the injector command signal at the injector connector during cranking to confirm ECM output presence.
  7. Swap cylinder 1 injector with another cylinder and retest; if the code follows the injector, replace the injector; if it stays on cylinder 1, suspect harness or ECM.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop. Injector replacement and harness repair costs differ widely; obtain local quotes.

When to see a pro

If the fault persists after harness and injector checks, or if ECM driver failure is suspected, have a qualified diesel technician perform ECM signal testing and module evaluation. Do not attempt high-pressure fuel system service without proper training and tools.

Sources

  1. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎