GM Duramax · Fuel Injector Group B Supply Voltage CircuitHigh

GM Duramax P2149: Fuel Injector Group B Supply Voltage Circuit/Open

P-Code P2149 (FMI N/A) — Fuel Injector Group B Supply Voltage Circuit/Open

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Quick Answer

P2149 means a fault in the shared supply voltage circuit for one injector group, which can cause rough running across multiple cylinders rather than a single-injector misfire.

Overview: GM Duramax P-Code P2149

Because injectors are wired in groups on this platform, a shared circuit fault - or even a single shorted injector - can affect several cylinders at once.

Repair Snapshot

Time

2 - 5 Hours

Difficulty

Advanced

Parts Cost

$100 - $1,200

Dealer Labor

$500+

Tools Required

  • Multimeter
  • Scan Tool
  • Wiring Diagram

What P-Code P2149 Means

P2149 means the PCM detected a fault in the supply voltage circuit feeding one bank (group) of fuel injectors, which can cause a noticeable misfire or rough running condition affecting multiple cylinders at once rather than a single injector issue.

Symptoms Drivers Notice

  • Rough running or misfire affecting multiple cylinders on one bank
  • Reduced power
  • Check engine light
  • Possible hard start or stall if the fault is severe

Most Likely Root Causes

Corroded or damaged group connector

Common

Disrupts supply voltage to the entire injector group.

Chafed harness near valve covers

Common

Vibration and heat cycling wear insulation over time in this area.

Internally shorted injector pulling down the shared circuit

Occasional

A single failed injector can affect the whole group's supply voltage.

Common Misdiagnoses (Don't Waste Parts)

Replacing all injectors in the group

Why it happens: Multi-cylinder misfire feels like it needs multiple parts.

Do this instead: Check individual injector resistance first - often only one injector is truly at fault, pulling down the shared circuit.

Overlooking the connector and harness

Why it happens: Focus goes straight to the injectors.

Do this instead: Inspect and test the group's wiring and connector before assuming injector failure.

Master Tech Commentary

Mechanic's Notes

Shop tip: a single shorted injector can sometimes pull down the shared supply circuit for its whole group. Check individual injector resistance within the group before assuming it's purely a wiring fault.

Step-by-Step Diagnostic Procedure

  1. Step 1: Inspect the injector harness connector for the affected group for corrosion or damage.
  2. Step 2: Check the supply voltage circuit with a multimeter for proper voltage reaching the injector group.
  3. Step 3: Trace the harness for chafing near the valve covers or injector wiring looms.
  4. Step 4: Verify the injector driver module (if separate from the PCM) is functioning correctly.
  5. Step 5: Check individual injector resistance within the affected group to rule out an internal injector short pulling down the shared circuit.

Professional service / OEM-level scan tools are recommended before clearing this fault for good.

Live Data & Freeze-Frame Tips

Monitor individual cylinder contribution data while testing - cylinders in the affected group showing a shared pattern of misfire point to a common circuit issue rather than individual injector wear.

Safety Warnings

  • Relieve fuel system pressure before disconnecting injector-related fittings.
  • Disconnect the battery before extensive injector wiring diagnosis.

When to Limp In vs Tow

If the misfire is severe enough to cause a rough idle or stalling risk, avoid extended driving until diagnosed.

Prevention Tips for Fleets & Owner-Operators

  • Inspect injector harness connectors during valve cover service.
  • Address minor misfire symptoms early before they progress.
  • Keep wiring protected from heat and vibration damage.

Related Fault Codes

P0300

Random/multiple cylinder misfire that can result from this shared circuit fault.

Frequently Asked Questions

Does this mean all injectors in that group are bad?

Not necessarily - often just one injector or the shared wiring is the actual cause.

Can I drive with this code?

Not recommended for long distances - multi-cylinder misfire can cause further engine strain and reduced fuel economy.

Is this an expensive repair?

It varies - a wiring fix is moderate cost, while multiple injector replacements add up quickly.

How do I know if it's one injector or the wiring?

Testing individual injector resistance within the group helps isolate whether one injector or the shared circuit is at fault.

Will this cause long-term engine damage?

Extended operation with a multi-cylinder misfire can increase wear, so prompt diagnosis is worthwhile.

More GM Duramax codes on this system

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