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Severity: High Code type: Generic (all makes)

P2149 Code: Fuel Injector Group B Supply Voltage Circuit/Open

The shared supply to the second injector group dropped out, often an intermittent wiring fault tied to heat.

At a glance

Severity: 4/5 – High4/5

Severity: High

Meaning
Fuel Injector Group B Supply Voltage Circuit/Open
System
Fuel & Air Metering · Powertrain
Safe to drive?
With caution
Typical repair cost
$100–$2,200
DIY difficulty
Hard

Direct-injection gasoline engines and common-rail diesels power their injectors from boosted voltage stages inside the ECU, and each stage feeds a group of injectors. P2149 reports that the supply circuit for group B is open or carries no current. What makes this code tricky in practice is that it's often intermittent. On many diesel trucks and some DI engines the injector wiring runs inside the valve cover and exits through a sealed pass-through connector; engine oil can creep along the wires into that connector, and heat cycles loosen terminals until the circuit drops out only when hot, or only over bumps. Another pattern is the code appearing only during a long, weak crank, when the ECU can't build its boost voltage because the batteries are tired. When group A shows up at the same time, stop looking at the group B wiring and check what both groups share.

Can I keep driving? If the engine runs smoothly and the code is stored rather than active, you can drive carefully to a shop. If cylinders are dropping out, expect sudden power loss and possibly stalling at low speed, so avoid highways and heavy traffic until it's repaired.

How to read P2149

How to read P2149P12213494
  1. P Powertrain
  2. 2 Generic (SAE)
  3. 1 Fuel & air metering
  4. 49 Specific fault

Symptoms

  • Intermittent stumble or several cylinders dropping out, then recovering
  • Fault appears mainly when the engine is hot or over rough roads
  • Code sets after a slow crank on a cold morning
  • Loss of power, sometimes limp mode or stalling at idle
  • Oil found inside an injector harness connector

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Oil wicking into the injector harness pass-through or group B connector 24%
  2. Harness chafed under the valve cover or against a bracket, opening when hot or moving 22%
  3. Loose or heat-fatigued terminals in the group B supply path 18%
  4. Weak batteries or poor cranking voltage stopping the ECU from building boost voltage 14%
  5. Poor ECU ground or power supply (usually sets group A codes too) 12%
  6. Internal ECU fault in the group B output stage 10%

Diagnosis step by step

Diagnostic flow: P21491Read freeze frame and code status2Test batteries and cranking voltage3Check ECU power and grounds4Look for oil in the injectorconnectors5Wiggle test with live data6Repeat the checks hot

  1. Read freeze frame and code status

    Check whether P2149 is active or stored, and look at engine temperature, rpm and battery voltage when it set. A code logged at cranking speed with low voltage points toward batteries; one logged hot at cruise points to wiring.

    Tools: OBD-II scanner

  2. Test batteries and cranking voltage

    Load-test the battery or both batteries on dual-battery diesels and watch voltage while cranking. If it dips below roughly 9.5 volts, fix that first: the ECU needs a stable supply to charge its injector boost circuit.

    Tools: Multimeter

  3. Check ECU power and grounds

    If P2146 is also stored, measure voltage drop on the ECU ground and power feeds under load. More than a few tenths of a volt on a ground is enough to make the boost stages misbehave.

    Tools: Multimeter

  4. Look for oil in the injector connectors

    Unplug the group B connectors at the valve cover or head pass-through and look for oil film or wet pins. Oil there means the seal has failed; cleaning helps briefly, but the seal or the harness section must be replaced.

    Tools: Flashlight, Gloves

  5. Wiggle test with live data

    Engine idling, watch misfire counters or cylinder contribution for the group B cylinders while gently moving the outside harness and connectors. A change the moment you move a section locates the fault; don't pull on wires under the valve cover with the engine running.

    Tools: OBD-II scanner

  6. Repeat the checks hot

    If nothing shows cold, repeat the continuity check from the ECU pin to each group B injector right after a drive, when the engine is fully warm. Heat-related opens often disappear within minutes of cooling down.

    Tools: Multimeter

Where the parts are

Ignition: coils and spark plugs per cylinder – P21491234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Replace batteries and recheck cranking Yes $180–$450
Replace pass-through connector seal and clean terminals No $150–$450
Replace internal injector harness No $300–$900
Repair ECU grounds and power feeds No $100–$300
Replace and program ECU No $900–$2,200

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Emissions / smog test impact

Will fail

With P2149 stored the check engine light is on and the vehicle fails a state OBD-II test. Intermittent faults often come back after clearing, so drive for several days after the repair before going to the test station.

Frequently asked questions

The code comes and goes. How do I catch it?

Use freeze frame to see the conditions and try to reproduce them: fully hot engine, rough road or cold crank. Then check wiring continuity and do the wiggle test under exactly those conditions.

Can weak batteries really set P2149?

Yes, on some engines. The ECU charges a capacitor-based boost circuit to fire the injectors; if voltage sags too far during a long crank it can't supply a group and logs the fault. It's worth ruling out before touching wiring.

Both P2146 and P2149 are stored. What does that mean?

Two groups failing together rarely means two separate wiring faults. Check the ECU's main power, grounds and battery voltage first, and the ECU itself only after those are confirmed.

Why is there oil in my injector connector?

Where the harness passes out of the valve cover or head, a seal keeps oil in. When it hardens, oil creeps along the wires by capillary action into the connector and upsets the circuit, especially when hot.

Sources