Diesel Trouble Codes

P0201 — Injector Circuit/Open - Cylinder 1 (LB7 Duramax)

P0201 indicates the ECM has detected an electrical fault in the fuel injector circuit for cylinder 1 on the LB7 Duramax.

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 the LB7 Duramax, injectors are Bosch units mounted under the valve covers and are a known weak point.1

Most likely causes

  1. Open or high-resistance in injector 1 harness or connector under valve cover — Corrosion, chafing, or loose pin at the injector 1 connector can create an open circuit detected by the ECM.1
  2. Failed injector 1 solenoid/electrical coil — Internal electrical failure of the injector solenoid produces an open circuit condition for cylinder 1.1
  3. ECM driver fault for cylinder 1 injector — Internal ECM injector driver failure can set an injector circuit/open code for the affected cylinder.1
  4. Wiring short to ground or power in injector 1 circuit — Damaged harness insulation can short the injector control wire, leading to an open or malfunction detection.1

How to diagnose

  1. Verify code P0201 is present and check for accompanying misfire codes P0301/P0300.
  2. Inspect valve cover harness and injector 1 connector for corrosion, oil intrusion, or damage; check continuity and resistance of injector 1 circuit.
  3. Measure injector 1 solenoid resistance and compare to spec; inspect for fuel in oil or balance-rate drift indicating injector body issues.
  4. Check ECM injector driver output and wiring integrity between ECM and valve cover connector.
  5. Clear codes and retest after repairs to confirm circuit integrity.

Parts and tools you may need

Rough cost and difficulty

Diagnostic labor varies; injector replacement on LB7 requires valve cover removal. Parts and labor costs depend on whether the fault is wiring or injector.

When to see a pro

If injector replacement is required, have a qualified diesel technician perform the work to ensure proper installation and coding. Seek professional help for ECM diagnostics or wiring repairs involving high-pressure fuel system components.

Sources

  1. Curated DTC seed — LB7 Duramax (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎