Diesel Trouble Codes

P0206 — Injector Circuit/Open - Cylinder 6 — LB7 Duramax

The ECM has detected an electrical fault in the cylinder 6 injector circuit on the LB7 Duramax. The LB7 injectors sit under the valve covers and are a known…

Updated October 15, 2026

What it means

The ECM has detected an electrical fault in the cylinder 6 injector circuit. On the LB7 Duramax the injectors are mounted under the valve covers and are a well-known weak point.1

Most likely causes

  1. Open or high-resistance in the cylinder 6 injector harness/connector under the valve cover — Inspect the under-valve-cover injector harness and connector for chafing, oil intrusion, corrosion, or loose terminals at cylinder 6. On the LB7 the injectors sit under the valve covers and are a well-known weak point; check the injector harness and connector under the valve cover, then the injector.1
  2. Failed cylinder 6 injector (internal coil/open) — A failed injector can present as an electrical open.1
  3. ECM driver or wiring fault to cylinder 6 injector — Wiring from the ECM to the valve-cover pass-through can be damaged or corroded, causing an open circuit to cylinder 6.1

How to diagnose

  1. Verify the code and freeze-frame; confirm P0206 is present and note engine conditions.
  2. Visually inspect the under-valve-cover injector harness and connector for cylinder 6 for oil, corrosion, chafing, or loose pins.
  3. Check continuity and resistance of the cylinder 6 injector circuit from the ECM connector to the injector connector, looking for opens or high resistance.
  4. Measure injector coil resistance at the injector connector and compare to spec; an out-of-range reading indicates a failed injector.
  5. If harness and injector test good, evaluate ECM driver output and related wiring for faults.
  6. Clear codes, run the engine and recheck for P0206 recurrence and accompanying misfire codes.

Specs and test values

CheckNormal readingWhen to measureSource
Injector balance ratesHealthy engines sit near ±2 mm³; values near ±4 mm³ or one cylinder far from the rest need a closer lookHot idle in Park, A/C offBD Diesel

Common mistake to avoid

Buying injectors on balance rates alone. Compression, rail pressure and the pressure regulator all move balance rates; confirm a suspect injector with a return-flow test before replacing it. Source: BD Diesel — LB7 injectors: balance rates and return tests.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
Injector wiring harness / under-valve-cover harness$50–$3002–5 hrsShop
Fuel injector (each)$250–$4502–4 hrsShop

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

High-pressure fuel systems are dangerous. If you are not experienced with diesel fuel systems, have a qualified diesel technician perform electrical testing and injector service. Do not attempt high-pressure fuel disconnection without proper training and tools.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

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