01 B1700 – Body Network Communication Fault: Module Data Loss • 02 Tire Bubbles: Understanding the Dangers and How to Address … • 03 The ABS Light That Changes How Your Brakes Behave Without W… • 04 Troubleshooting a Manual Transmission: FAQs and Solutions • 05 The Benefits of Catalytic Converters in Vehicle Exhaust Sys… • 06 Why are Catalytic Converters Stolen and How to Prevent It • 07 From Lap Belts to Three-Point Safety Belts: A History of Ve… • 08 How to Clean Piston Ring Grooves: A Complete Guide • 09 The Mechanic Who Rebuilt 100 Engines Explains What Drivers … • 10 What Causes a Car Engine to Use More Water? •

DTC codes / P21xx · Fuel and air metering / P2151

P2151Fuel Injector Group 'B' Supply Voltage Circuit High

P2151 means the powertrain control module (PCM) has detected an abnormally high voltage on the supply circuit feeding fuel injector group 'B', which is a set of injectors wired together on the same power feed. The PCM expects this circuit to sit near battery voltage when the injectors are off and to drop only slightly when they fire, so a reading above the expected threshold tells the module that the supply line is shorted to voltage or has lost its normal ground path.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaFuel and air metering

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire that may be intermittent and worse when the engine is hot
  • A dead miss on the cylinders served by injector group 'B' if the circuit is fully shorted
  • Poor fuel economy or a rich-running smell from unburned fuel in the affected cylinders
  • Reduced engine power or limp-home mode on some vehicles when the fault is active
  • Hard starting or a stall after startup when the injector driver is disabled by the PCM

Common causes, most likely first

  1. Chafed or shorted injector supply wire touching a higher-voltage source or another power wire in the harness
  2. Corroded, loose or backed-out terminal at the injector group 'B' connector or at the PCM connector
  3. Failed fuel injector with an internally shorted coil winding pulling the supply circuit high
  4. Open or high-resistance ground at the injector group 'B' ground point, which raises the measured supply voltage
  5. Damaged PCM injector driver or internal supply circuit after a shorted injector or harness fault
  6. Aftermarket alarm, remote starter or accessory wiring tapped into the injector supply circuit
  7. Water intrusion into the harness or connector causing intermittent voltage bleed onto the supply line

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P2151, then clear the code and verify whether it returns immediately or only under specific conditions
  2. Inspect the injector group 'B' harness and connectors for chafing, corrosion, pushed pins and signs of water intrusion
  3. Measure supply voltage at each injector in group 'B' with the key on and engine off, comparing against battery voltage and the other injector groups
  4. Check resistance and continuity of the injector group 'B' ground circuit back to the engine block and battery negative
  5. Disconnect the injectors one at a time and watch the supply voltage to isolate a shorted injector from a harness fault
  6. Load-test the supply wire with a bulb or test light to confirm it can carry current without a voltage drop
  7. If the harness and injectors test good, perform a PCM driver test or substitute a known-good module to rule out an internal PCM fault

What a high injector supply voltage really means

  • A high supply voltage reading often comes from a missing ground rather than a true short to power, because the PCM measures the circuit relative to ground and a lifted ground makes the supply line look elevated.
  • Injector group 'B' is a wiring grouping, not a physical bank, so the affected injectors may be spread across both sides of a V-engine and the misfire can seem random.
  • A shorted injector coil can pull the supply circuit high and damage the PCM driver if the code is ignored, so diagnosing the injectors before replacing the module is critical.
  • Aftermarket accessories tapped into the injector harness are a common hidden cause, especially on vehicles with remote starters or alarm systems installed after purchase.
  • P2151 can set intermittently from a harness rubbed through only at a certain engine torque angle, so a wiggle test of the harness while watching live voltage data often finds it when a static meter test does not.

Can I keep driving with P2151?

You can usually drive a short distance to a repair shop if the engine still runs smoothly, but avoid heavy throttle and long trips because a shorted injector circuit can damage the PCM driver and cause a misfire that overheats the catalytic converter. If the engine is misfiring badly or the check engine light is flashing, stop driving and have the vehicle towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage