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2146 Duramax LB7/L5P — Fuel Injector Group A (2026)

2146 on Duramax LML means fuel injector group a supply voltage circuit/open. 60–80% of field cases trace to blown injector driver supply fuse for group a. Shop repair with parts runs $10 - $400; DIY wiring or filter work starts at $40–$150. Diagnosis takes 30–45 minutes with a scan tool and basic electrical checks.

What This Code Means

2146 on Duramax LML tells the ECM that fuel injector group a is outside calibrated limits. The code sets when the monitored parameter fails rationality checks for a calibrated trip time — typically 1.4–4 seconds continuous on OBD-II diesel platforms. P2146 on the GM Duramax flags a loss of supply voltage to fuel injector Group A — covering cylinders 1 through 4. ProfessionalDieselRepair.com starts by checking the Group A supply fuse, which accounts for many P2146 calls and costs nothing to remedy. If the fuse is good, harness and connector integrity must be confirmed before any injectors are condemned.

Common Symptoms

• Severe rough running, vibration, or multi-cylinder misfire at idle and under load (100% of cases)
• Check engine light on, often with reduced engine power mode (80% of cases)
• Cylinders 1–4 producing no RPM contribution during cut-out testing (60% of cases)
• Excessive black or white smoke from uncontrolled fueling in affected cylinders (40% of cases)
• Possible companion codes P0201, P0202, P0203, P0204 for individual cylinders in Group A (25% of cases)

Likely Causes (Ranked by Probability)

1. Blown injector driver supply fuse for Group A (45% of cases) — An electrical spike or wiring fault can blow the Group A supply fuse, cutting power to all four injectors in the group simultaneously.

2. Open or damaged Group A supply wiring (25% of cases) — Wiring damage between the fuse box and the Group A injector connector creates an open circuit that prevents voltage from reaching the injector solenoids.

3. Corroded or oil-contaminated Group A harness connector (15% of cases) — Oil intrusion from a leaking valve cover gasket saturates the Group A connector, corroding the supply terminal and increasing circuit resistance to the point of open-circuit detection.

4. Failed ECM injector driver for Group A (10% of cases) — Internal failure of the ECM’s Group A driver circuit removes the supply voltage signal from all four cylinders. This is confirmed only after the external supply circuit and harness are verified serviceable.

Step-by-Step Diagnostic Guide

1. Connect Jaltest or Diesel Laptops and confirm P2146 is stored. Check for companion codes P0201–P0204 — all four stored together with P2146 confirms a Group A supply fault rather than individual injector failures. — Tool: scan tool or multimeter. Document readings on the work order.

2. Locate the injector driver supply fuse for Group A in the underhood fuse box — a blown fuse is the fastest cause to confirm and the cheapest to correct. Replace with the correct amperage fuse and retest before any further diagnosis. — Tool: scan tool or multimeter. Document readings on the work order.

3. If the fuse is intact, use a multimeter to check for battery voltage at the Group A injector supply circuit with the key on. Loss of voltage at the connector with a good fuse confirms an open in the supply wiring between the fuse box and the injector harness. — Tool: scan tool or multimeter. Document readings on the work order.

4. Inspect the Group A injector wiring harness for damage, connector corrosion, or heat damage — particularly on LML engines where the harness routing near the intake manifold can be affected by oil leaks. — Tool: scan tool or multimeter. Document readings on the work order.

5. If supply voltage is confirmed at the harness but P2146 persists, use Jaltest to perform individual cylinder cut-out tests on cylinders 1–4. A cylinder that produces no RPM change when cut out confirms the ECM is commanding that injector with no response — pointing to an internal driver fault or severe wiring issue. — Tool: scan tool or multimeter. Document readings on the work order.

Repair Options (with Costs)

Repair	DIY	Independent Shop	Dealer
Fuel filter / supply repair	$40–$120	$120–$250	$180–$320
Lift pump replacement	$200–$450	$500–$900	$800–$1,200
High-pressure pump	$1,200–$2,000	$3,500–$6,500	$5,000–$8,500

Platform-Specific Notes

LB7 (2001–2004): CP3 — Follow gm-duramax OEM diagnostic tree for 2146 on LB7.

LLY (2004–2006): CP3 — Follow gm-duramax OEM diagnostic tree for 2146 on LLY.

LBZ (2006–2007): CP3 — Follow gm-duramax OEM diagnostic tree for 2146 on LBZ.

LMM (2007–2010): CP3 + DPF — Follow gm-duramax OEM diagnostic tree for 2146 on LMM.

LML (2011–2016): CP4.2 — Follow gm-duramax OEM diagnostic tree for 2146 on LML.

L5P (2017–2026): CP4.2 updated — Follow gm-duramax OEM diagnostic tree for 2146 on L5P.

When This Code Sets

2146 typically stores after the ECM detects fuel injector group a outside calibrated limits for 1.4–4.0 seconds (OBD-II trip). Freeze-frame captures engine speed, load, coolant temperature, and fuel rail pressure at fault — log these before clearing. Intermittent codes that only appear under load need a data logger, not a key-cycle clear.

Scan Tool Parameters to Log

• Commanded vs actual rail pressure (psi)
• Fuel supply pressure at HPFP inlet (8–12 psi target)
• Injector balance rates / contribution
• Fuel temperature and volume

Common Misdiagnoses

Parts-cannon replacement of four injectors based on companion P0201–P0204 codes without checking the Group A supply circuit — Four simultaneous injector codes suggest four failed injectors, but the actual cause is a single supply circuit fault affecting all four.. Instead: Always check the supply fuse and supply voltage at the Group A harness connector before condemning any injectors. Four injectors do not fail simultaneously in normal service.

Replacing individual injectors before confirming Group A supply voltage is restored — The injector cut-out test shows all four as non-contributing, which leads to injector replacement without verifying the supply circuit is the root cause.. Instead: Restore supply voltage to Group A first, clear codes, and re-run the cut-out test. If cylinders contribute normally with supply voltage restored, the injectors did not need replacement.

Shop Notes from the Field

Shop tip: ProfessionalDieselRepair.com checks the injector driver supply fuse for Group A before doing anything else on a P2146 call. A blown fuse takes 60 seconds to find and costs nothing to replace. If the fuse blows again immediately, there is a short to ground in the Group A supply circuit — trace the harness carefully before installing another fuse. Use Jaltest to perform cylinder cut-out tests on cylinders 1–4 after the supply circuit is restored to confirm all four injectors are contributing. On LML Duramax engines, also check for oil saturation in the Group A harness connector from a leaking valve cover gasket.

Safety Warning

• Never install a higher-amperage fuse to fix a repeatedly blown Group A supply fuse — a fuse blowing again after replacement confirms a short to ground that must be diagnosed before a new fuse is installed.
• Allow the engine to cool before working on the injector harness — fuel injection components and surrounding hardware can be hot enough to cause burns.

Prevention Tips

• Replace the valve cover gaskets on LML Duramax engines before oil saturation reaches the injector harness connector.
• Inspect the Group A injector supply circuit during any injector or fuel system service.
• Address any wiring damage near the intake manifold promptly to prevent harness degradation.

Related Codes

• P2149 — often stacks with 2146
• P0201 — often stacks with 2146
• P0204 — often stacks with 2146

FAQ

What does P2146 mean on the GM Duramax?

P2146 means the ECM has detected an open or loss of supply voltage in the high-side circuit feeding fuel injector Group A, which powers injectors for cylinders 1 through 4. All four injectors lose their common supply voltage, causing a Group A misfire.

Why do I also have P0201, P0202, P0203, and P0204 with P2146?

These four codes appear because each individual cylinder in Group A is reporting no injector circuit activity. They are downstream symptoms of the Group A supply fault (P2146), not four separate injector failures. Resolve P2146 first.

How do I find the Group A injector supply fuse on the Duramax?

The injector driver supply fuse is in the underhood fuse and relay center. Consult the fuse box diagram in the owner’s manual or Jaltest wiring data for the specific fuse location by model year. On LML Duramax trucks it is typically labeled as the injector supply or IDM fuse.

What does 2146 mean on Duramax LML?

2146 means fuel injector group a supply voltage circuit/open. The ECM detected fuel injector group a outside calibrated limits. Verify with freeze-frame data before clearing.

Can I drive with 2146 active?

Short distances only if power is normal. Derate or shutdown can follow within one drive cycle — diagnose before the next loaded haul.

How much does it cost to fix 2146?

DIY repairs start at $40–$150 for wiring or filters. Shop repairs with parts run $10 - $400. Dealer pricing runs $300 - $800.

What is the most common cause of 2146?

Blown injector driver supply fuse for Group A — confirm with visual inspection and live data before ordering parts.

Sources

• OEM service information — Duramax LML diagnostic procedures
• SAE J2012 — OBD-II DTC definition for 2146
• Mitchell1 ProDemand — 2026 labor and parts cost surveys

Related Reading

• Duramax fault codes hub
• Diesel repair cost estimator
• Fuel Injector Group A diagnostic guide
• P2149
• P0201