P0202 — Injector Circuit/Open - Cylinder 2 — LLY / LBZ / LMM Duramax
Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. P0202 indicates the ECM has detected an electrical fault in the fuel injector circuit for cylinder 2.
What it means
The engine control module has detected an electrical fault in the fuel injector circuit for cylinder number two. On LLY/LBZ/LMM Duramax, injectors are Bosch common-rail units mounted externally (not under valve covers) and the platform uses CP3 common rail with pump-mounted fuel pressure regulator.1
Most likely causes
- Open or high resistance in injector 2 harness/connector — External injector wiring and connector for cylinder 2 can develop opens, corrosion, or terminal fretting leading to circuit malfunction detection.1
- Short to ground or short to voltage in injector 2 circuit — Chafed harness or damaged insulation can cause a short that the ECM flags as a circuit malfunction.1
- Faulty injector 2 solenoid/electrical coil — Internal electrical failure of the injector solenoid produces an out-of-range circuit signature.1
- ECM driver fault for injector 2 — Internal ECM injector driver issue can set a circuit code for a specific cylinder.1
How to diagnose
- Verify code P0202 is present and check for accompanying misfire codes P0300/P0302; platform-specific misfire contributors include fuel-rail pressure control/CP3/regulator/injector balance.
- Inspect external injector 2 connector and harness for damage, corrosion, oil intrusion, and proper seating; injectors are externally mounted on LLY/LBZ/LMM.
- Perform pin-to-pin continuity and isolation tests of injector 2 circuit from ECM connector to injector connector; compare resistance to other cylinders.
- Measure injector 2 solenoid resistance per service spec and compare to cylinders 1,3,4,5,6,7,8; significant deviation suggests injector electrical fault.
- Check ECM injector driver outputs with a lab scope during commanded injection; abnormal waveform indicates wiring or ECM issue.
- Clear codes, run engine and monitor for P0202 reset; if code returns with no wiring fault, suspect injector or ECM.
- Note LLY/LBZ/LMM use CP3 common rail, pump-mounted fuel pressure regulator, VGT turbo, glow plugs + control module, EGR/DOC (+DPF on LMM only), no DEF/SCR.
Parts and tools you may need
- Digital multimeter
- Lab scope
- Terminal release tools
- Dielectric grease
- Service information for injector resistance specs
Tools you’ll need
- OBD-II scan tool — Read and clear P0202 and related misfire codes, then monitor live data and injector balance rates during a test drive to confirm the fault returns.
- digital multimeter — Measure injector 2 solenoid resistance and perform continuity/isolation tests from ECM to injector connector to find opens, shorts, or high resistance.
- lab scope — Capture ECM injector driver waveform for cylinder 2 during commanded injection to identify abnormal drive signals versus wiring or ECM faults.
- fuel pressure gauge — Verify CP3 rail pressure control is normal so fuel delivery issues are not masking the electrical injector circuit fault.
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) | $300–$550 | 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 circuit tests pass but P0202 persists, or if injector replacement is considered, have a qualified diesel technician perform injector electrical testing and ECM verification. Do not attempt high-pressure fuel system service without proper training and safety equipment. High-pressure fuel lines are safety-critical; diagnosis only, no step-by-step repair instructions here. If misfire or performance issues continue, professional diagnosis is recommended.
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: P0202 on the LLY-LMM 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
Run a LLY / LBZ / LMM Duramax? This goes straight to the editor — it is not published.