P0201 — Injector Circuit/Open - Cylinder 1 — L5P Duramax
Diagnostic reference for P0201 on L5P Duramax (2017–present).
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
- Open or high resistance in injector 1 wiring harness or connector — Inspect harness for chafing, pin corrosion, or loose terminals at injector 1 and ECM. Check continuity and isolation to ground/power.1
- Failed injector 1 solenoid coil (open circuit) — Denso common-rail solenoid injectors are externally mounted on L5P. An open coil triggers P0201–P0208.1
- ECM driver fault for injector 1 — Internal ECM injector driver failure can set circuit/open code. Verify with known-good harness and injector before condemning ECM.1
- Poor ground or power supply to injector bank — Shared power/ground issues can appear as a single-cylinder circuit fault. Verify injector supply voltage and ground integrity.1
How to diagnose
- Verify code and freeze frame; confirm P0201 is current and not historical.
- Visually inspect injector 1 connector and harness for damage, oil intrusion, or corrosion.
- Measure injector 1 solenoid resistance per service spec and compare to other cylinders.
- Perform pin-to-pin continuity from injector 1 connector to ECM harness connector; check for opens/shorts to ground or battery.
- Command injector circuit test with scan tool if available; observe ECM driver feedback.
- Swap injector 1 electrical connector with adjacent cylinder to see if code follows wiring.
- If wiring and injector test good, evaluate ECM driver output.
Parts and tools you may need
- Digital multimeter
- Scan tool with bi-directional control
- Terminal release tools
- Dielectric grease
- Service information wiring diagram
Tools you’ll need
- digital multimeter — Measures injector 1 solenoid resistance and pin-to-pin continuity to ECM to find opens, shorts, or high resistance in the circuit.
- OBD-II scan tool — Confirms P0201 is current, reviews freeze frame, and can command injector circuit tests to observe ECM driver feedback.
- inspection light — Provides clear illumination for visual inspection of injector 1 connector and harness for damage, oil intrusion, or corrosion.
- terminal release tool set — Allows safe removal and reseating of injector 1 connector terminals for inspection and swap testing without 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) | $400–$700 | 1.5–3 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 ECM driver is suspected or high-pressure fuel system opening is required, have a qualified diesel technician perform diagnosis and repair. Do not service high-pressure fuel components without proper training and safety equipment.
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
Repair videos: P0201 on the L5P Duramax
Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.
Spotted an error, or something missing? Tell us
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