Faulty input voltage sensor B on battery charger A; Damaged or chafed wiring in the sensor circuit, causing a short to voltage; Corroded, loose, or disconnected electrical connector at the sensor or control module; Failed battery charger A assembly with an internal fault; Powertrain control module software error or internal circuit fault; High resistance in the ground circuit for the sensor, skewing the voltage reading; Aftermarket accessories improperly wired into the charger circuit

DTC codes / P0Exx · Hybrid propulsion / P0EFA

P0EFABattery Charger A Input Voltage Sensor B Circuit High

Q: What does code P0EFA mean?

Battery Charger A Input Voltage Sensor B Circuit High. P0EFA indicates that the powertrain control module has detected an abnormally high voltage on the input voltage sensor circuit for battery charger A, sensor B. This sensor monitors the voltage feeding the charger, and a high reading tells the module that the circuit is seeing more voltage than expected, which can affect charging system operation and trigger the warning light.

P0EFA indicates that the powertrain control module has detected an abnormally high voltage on the input voltage sensor circuit for battery charger A, sensor B. This sensor monitors the voltage feeding the charger, and a high reading tells the module that the circuit is seeing more voltage than expected, which can affect charging system operation and trigger the warning light.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message
Often no symptoms besides the warning light
Charging system warning lamp may also be on
Battery may not charge properly, leading to a no-start or slow crank condition
Electrical accessories may behave erratically or dim
Possible reduced engine performance or limp mode in some vehicles

Common causes, most likely first

Faulty input voltage sensor B on battery charger A
Damaged or chafed wiring in the sensor circuit, causing a short to voltage
Corroded, loose, or disconnected electrical connector at the sensor or control module
Failed battery charger A assembly with an internal fault
Powertrain control module software error or internal circuit fault
High resistance in the ground circuit for the sensor, skewing the voltage reading
Aftermarket accessories improperly wired into the charger circuit

How to diagnose and fix it

Scan all modules and record freeze-frame data to confirm the code is current and not history
Visually inspect the sensor, connector, and wiring for damage, corrosion, or loose pins
Measure reference voltage and signal voltage at the sensor connector with a digital multimeter and compare to manufacturer specifications
Check the sensor ground circuit for excessive resistance with a voltage drop test
Back-probe the signal wire at the control module to rule out a wiring short to voltage
If wiring and connectors are good, test or replace the input voltage sensor B or battery charger A assembly as directed by service information
Clear codes and verify the repair by running the charger through its operating range and confirming no code returns

What a high charger input voltage really means

A short to voltage on the signal wire is a common cause that many technicians miss because they replace the sensor first without checking the harness.
The code can set intermittently from a poor connection that only acts up under vibration or temperature changes, so a wiggle test of the harness is essential.
A weak or failing battery can cause erratic charger operation and set this code, so always load-test the battery before condemning the charger.
Aftermarket accessories tapped into the charger circuit can back-feed voltage and trigger a high input signal, which is often overlooked during diagnosis.
This code does not always mean the charger itself has failed; the fault may lie entirely in the wiring or connectors between the sensor and the control module.

Can I keep driving with P0EFA?

You can usually drive the vehicle short distances to a repair shop, but avoid long trips and heavy electrical loads because a charging system fault can leave you stranded with a dead battery. If the battery warning light is on or the vehicle is slow to crank, stop driving and arrange a tow.

Tools that help

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