P2147 — Injector Group “A” Supply Voltage Circuit Low

Category

Powertrain → Fuel System (Electronic Injector Control)

What it means (plain English)

This code sets when the ECM detects the voltage in the Group “A” injector supply circuit is lower than expected. Unlike P2146 (circuit open), this means voltage is present but too weak to power injectors correctly.

Symptoms

  • MIL (Check Engine Light) on
  • Hard starting or extended cranking
  • Rough idle and poor throttle response
  • White/black smoke from unburned fuel
  • Engine derate or limp mode possible

Priority Level

High —
Low supply voltage can cause misfires or injector dropout, risking engine damage or breakdown.

Common Causes

  • Weak battery or poor charging system
  • High resistance in injector Group “A” wiring harness
  • Corroded, loose, or oil-soaked connectors
  • Short-to-ground pulling voltage down
  • Failing ECM injector driver circuit

How Pros Diagnose It

  1. Check battery/charging system voltage — confirm 13.8–14.5V running.
  2. Live data — monitor injector Group “A” voltage while cranking.
  3. Inspect harness/connector for corrosion, heat damage, or oil intrusion.
  4. Voltage drop test across harness — look for excessive resistance.
  5. Load test injectors — ensure one shorted injector isn’t pulling voltage down.

Likely Fixes

  • Repair/replace corroded wiring or connectors
  • Replace failed battery/alternator (if voltage supply issue)
  • Replace faulty injector(s) if shorted
  • Replace ECM if driver circuit is bad

Related/Companion Codes

  • P2146 — Circuit/Open
  • P2148 — Circuit High
  • P2150–P2155 — Injector Group “B” faults
  • P0201–P0208 — Individual injector codes

Tech Notes

  • Duramax LML often logs this when harness connectors at the valve cover corrode.
  • Cummins ISX — shorted injector coil can pull Group “A” circuit voltage low.

Severity: High — Repair Soon
A P2147 code means injector Group “A” isn’t receiving enough voltage. This causes rough running, hard starts, or loss of power. Fixing wiring, connectors, or injectors quickly prevents major downtime.

🔗 Sources: