P0651: The 5-volt reference supply (circuit B) that powers a group of sensors is out of range

Sensor Reference Voltage B Circuit

Severity: Inspect soon

One failing reference circuit can knock out several sensors at once, which can cause stalling, poor running or limp mode. It is often a single shorted sensor, so it is worth finding soon.

It gets more serious if:

Stop: Stop driving if the engine stalls, stumbles badly or goes into limp mode, especially in traffic.

Source: how we rate severity

P0651 in short

P0651 means the computer found a problem with sensor reference voltage circuit B, the shared 5-volt supply for a group of sensors. A shorted sensor, damaged wiring or a bad connector is the usual cause, and the computer itself is rare. Several sensors may act up at once, so get it checked soon.

The engine computer sends a regulated 5-volt reference to several sensors, such as the throttle, pedal, pressure and position sensors. The circuit is split into groups, labeled A, B and so on, and the manufacturer service information says which sensors share circuit B.

P0651 sets when the voltage on that supply is out of range. The usual cause is one sensor or its wiring shorted to ground or another wire, which pulls the whole supply down. A bad connector or, rarely, the computer can do the same.

Since all sensors on the circuit lose their reference together, you may see several other codes and symptoms like poor running or limp mode.

Most likely causes

Cause 1: A sensor on the shared 5V circuit is shorted
Common general cause
Why it ranks here
Both references describe the supply being pulled out of range by a failing sensor or its wiring, and suggest unplugging sensors one at a time to find it.
What would change this
Rises if the voltage returns to normal when one sensor is unplugged. Falls if no sensor change affects it.
Cause 2: Damaged wiring or a bad connector
Common general cause
Why it ranks here
Chafed wires, corrosion or loose terminals can short or open the reference supply.
What would change this
Rises if wiring inspection finds damage. Falls if the harness tests fine.
Cause 3: Secondary code with P06DE on GM engines (broken oil piston nozzles)
Supported by vehicle data
Why it ranks here
GM PIP5247A says P0651 may be stored with P06DE and points to broken oil piston nozzles when oil pressure is low or the oil pan is removed.
What would change this
Rises on a covered 2013-2019 GM model with P06DE stored and low hot oil pressure. Falls on other vehicles or without P06DE.
Cause 4: Engine computer fault
Possible — needs testing
Why it ranks here
Both sources treat the computer as a rare cause, only after sensors and wiring are ruled out.
What would change this
Rises only if the reference stays wrong with all sensors unplugged and wiring tested.
How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

Step 1: Read all stored codes and note which other sensor codes appear with P0651. They show which sensors share the failing supply.
Low riskTool: OBD-II scan tool
- IfP06DE is also stored on a 2013-2019 GM model
  It meansGM links the two codes; follow the P06DE diagnostics and bulletin PIP5247A.
  Points to: Secondary code with P06DE on GM engines (broken oil piston nozzles)
- IfSeveral sensor codes are stored together
  It meansA shared reference is the likely issue; check which sensors share circuit B in the service information.
  Go to step 2
- IfOnly P0651 is stored
  It meansInspect wiring and connectors first.
  Go to step 3
Step 2: Have a technician unplug the sensors on circuit B one at a time with the key on and watch the reference voltage.
Best left to a shopTool: scan tool, multimeter
Warning:Unplug sensors only with the ignition off, and avoid probing airbag circuits.
- IfThe voltage returns to normal when one sensor is unplugged
  It meansThat sensor is shorted.
  Points to: A sensor on the shared 5V circuit is shorted
- IfVoltage stays wrong
  It meansInspect wiring and connectors.
  Go to step 3
Step 3: Inspect the harness and connectors serving circuit B for chafing, corrosion, water or pushed-out pins.
Low risk
- IfDamage is found
  It meansRepair the wiring or connector.
  Points to: Damaged wiring or a bad connector
- IfEverything is fine
  It meansThe computer may be at fault; get a professional diagnosis.
  Points to: Engine computer fault

Symptoms

Check engine light on
Poor running or reduced power
Several other sensor codes at once
Stalling Gets more serious: stop and have it checked.

How to fix

Step 1: Read all stored codes and write them down; the other codes help find which sensors share the failing supply.

Parts and cost context

Engine control module (ECM / PCM):The computer is rarely the cause; find the shorted sensor or wiring first. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

2013–2019 · Malibu
Supported by vehicle data
GM says P0651 can be stored alongside P06DE; the bulletin points to broken oil piston nozzles when oil pressure is low or the oil pan is removed. Applies to many 2013-2019 GM models. Whether it is current is not verified.

PIP5247AStatus unverified
P06DE with P0651 possibly also set: inspect oil piston nozzles
2013–2019camaro, colorado, equinox, impala, malibu, traverse, blazer · issued May 17, 2021 · NHTSA 10193443
GM says P0651 may be stored with P06DE; follow the P06DE diagnostics and, if they lead to the oil pan or hot oil pressure is low, inspect and replace broken oil piston nozzles.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Bentley

2021–2024 · Continental
Supported by vehicle data
Bentley technical information describes which sensors share ECM 5V reference circuit B and how to isolate faults for P0651, P0652 and P0653 on 2021-2024 Continental GT and Flying Spur. Whether it is current is not verified.

2081243/2Status unverified
ECM 5V reference circuits A, B and C: sensors per circuit and isolation guidance
2021–2024continental-gt, continental-gt-cabrio, flying-spur · issued July 16, 2026 · NHTSA 11035305
Technical information listing the sensors on each ECM 5V reference circuit and guidance for isolating faults when P0651, P0652 or P0653 and the related A and C circuit codes are stored.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P0651 yet.

All Engine computer (ECM/PCM) codes

P0651 questions

Why do I have several sensor codes with P0651?

Sensors on the same 5-volt supply lose their reference together, so a single short can set codes for each of them.

Sources and review

P0651 Code: Sensor Reference Voltage B Circuit Open — Kelley Blue Book
P0651 OBD Code: Sensor Reference Voltage B Circuit Open — PartsAvatar
GM PIP5247A: P06DE (with P0651 possibly also set) and broken oil piston nozzles — General Motors / NHTSA , May 17, 2021
Bentley TPI 2081243/2: ECM 5V reference circuits (A, B and C), including P0651/P0652/P0653 — Bentley Motors / NHTSA , July 16, 2026

Last reviewed: October 15, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

Severity: Inspect soon

Most likely causes

Cause 1: A sensor on the shared 5V circuit is shorted

Cause 2: Damaged wiring or a bad connector

Cause 3: Secondary code with P06DE on GM engines (broken oil piston nozzles)

Cause 4: Engine computer fault

What to test first

Step 1: Read all stored codes and note which other sensor codes appear with P0651. They show which sensors share the failing supply.

Step 2: Have a technician unplug the sensors on circuit B one at a time with the key on and watch the reference voltage.

Step 3: Inspect the harness and connectors serving circuit B for chafing, corrosion, water or pushed-out pins.