Diesel Trouble Codes

P0206 — Injector Circuit/Open - Cylinder 6 (5.9 Cummins Common Rail)

Diagnostic reference for P0206 on 5.9L Cummins Common Rail 2003-2007. Covers what the code means, how to diagnose the injector circuit/open fault for cylinder…

Updated September 2, 2026

What it means

The ECM has detected an electrical fault in the fuel injector circuit for cylinder number six. On the 5.9L Cummins Common Rail 2003-2007 ISB, injectors are Bosch common-rail solenoid type and electrical faults show as P0201-P0206; contribution/balance faults are P0263-family. This platform uses a CP3 pump with FCA/MPROP and rail pressure sensor/relief valve, has no EGR/DPF/SCR/DEF, no VGT, grid heater not glow plugs.12345

Most likely causes

  1. Open or high resistance in cylinder 6 injector wiring/connector — Inspect the injector harness and connector at cylinder 6 for chafing, oil intrusion, corrosion, or loose terminals. Check continuity and isolation of the injector control circuit from ECM to injector. Compare resistance to adjacent cylinders.12345
  2. Failed or internally open Bosch common-rail solenoid injector on cylinder 6 — A solenoid injector with an open coil will set P0206. Electrical check of injector resistance at the connector versus spec and comparison to other cylinders helps isolate an injector fault from wiring.12345
  3. ECM driver fault for cylinder 6 injector circuit — If wiring and injector test good, the ECM internal driver for cylinder 6 may be faulty. Verify power/ground and reference signals to ECM and inspect for water intrusion before condemning ECM.12345
  4. Chafed engine harness near valve cover / injector rail — The injector harness runs close to hot/valve-cover areas and can chafe. Look for rubbed-through insulation causing intermittent open/short, especially on cylinder 6.12345

How to diagnose

  1. Verify code and freeze frame; confirm P0206 is present and not accompanied by rail pressure or contribution codes.
  2. Visually inspect cylinder 6 injector connector and harness for damage, oil, corrosion, or loose pins.
  3. Measure injector solenoid resistance at cylinder 6 connector and compare to cylinders 1-5; look for open/infinite resistance.
  4. Check continuity and isolation of injector control circuit from ECM connector to cylinder 6 injector connector; inspect for chafing along harness route.
  5. Inspect ECM connectors for corrosion/moisture; verify ECM power and ground circuits.
  6. Clear codes, run engine and monitor for P0206 reset; if code returns with good wiring and injector resistance, suspect ECM driver.
  7. Note: contribution/balance faults are P0263-family; P0206 is electrical circuit/open, not a performance/balance issue.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop. Electrical diagnosis is typically labor-intensive; injector replacement requires proper coding and fuel system handling. Obtain quotes from qualified diesel technicians.

When to see a pro

If wiring tests good but code persists, or ECM driver is suspected, have a qualified diesel technician perform ECM output tests and injector circuit verification. Do not attempt high-pressure fuel system service without proper training and tools.

Sources

  1. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  3. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  4. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  5. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎