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.
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
- 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
- Failed injector 1 solenoid/electrical coil — Internal electrical failure of the injector solenoid produces an open circuit condition for cylinder 1.1
- ECM driver fault for cylinder 1 injector — Internal ECM injector driver failure can set an injector circuit/open code for the affected cylinder.1
- 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
- Verify code P0201 is present and check for accompanying misfire codes P0301/P0300.
- Inspect valve cover harness and injector 1 connector for corrosion, oil intrusion, or damage; check continuity and resistance of injector 1 circuit.
- Measure injector 1 solenoid resistance and compare to spec; inspect for fuel in oil or balance-rate drift indicating injector body issues.
- Check ECM injector driver output and wiring integrity between ECM and valve cover connector.
- Clear codes and retest after repairs to confirm circuit integrity.
Specs and test values
| Check | Normal reading | When to measure | Source |
|---|---|---|---|
| Injector balance rates | Healthy engines sit near ±2 mm³; values near ±4 mm³ or one cylinder far from the rest need a closer look | Hot idle in Park, A/C off | BD 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
- Digital multimeter
- Scan tool with live data
- Injector harness test leads
- Valve cover gasket set
Tools you’ll need
- digital multimeter — Measures injector 1 solenoid resistance and harness continuity to find open or high-resistance faults.
- OBD-II scan tool — Confirms P0201 and related misfire codes and monitors injector balance rates after repair.
- fuel pressure gauge — Verifies rail pressure stability while testing injector electrical circuit integrity.
- inspection light — Illuminates the under-valve-cover harness and connector for corrosion, oil intrusion, or damage.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| Wiring or connector repair | $10–$100 | 1–4 hrs | DIY with tools and a manual |
| Injector wiring harness / under-valve-cover harness | $50–$300 | 2–5 hrs | Shop |
| Fuel injector (each) | $250–$450 | 2–4 hrs | Shop |
| ECM/PCM replacement (programmed) | $600–$2,000 | 1–3 hrs | Shop |
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
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.
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
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