Faulty voltage sensor on the DC/DC converter circuit; Damaged or corroded wiring or connector at the sensor or converter; High resistance in the sensor ground circuit; Internal failure within the DC/DC converter affecting sensor output; Poor connection at the powertrain control module connector; Software calibration issue in the control module (less common)

DTC codes / P0Exx · Hybrid propulsion / P0E38

P0E38DC/DC Converter Voltage Sensor B Low

Q: What does code P0E38 mean?

DC/DC Converter Voltage Sensor B Low. P0E38 indicates that the voltage sensor circuit for the DC/DC converter's secondary side is reporting a voltage below the expected range, which the powertrain control module uses to monitor converter performance. The computer detects this when the sensor signal stays lower than the calibrated threshold for a set time, often pointing to a wiring issue, a failing sensor, or a problem within the converter itself.

P0E38 indicates that the voltage sensor circuit for the DC/DC converter's secondary side is reporting a voltage below the expected range, which the powertrain control module uses to monitor converter performance. The computer detects this when the sensor signal stays lower than the calibrated threshold for a set time, often pointing to a wiring issue, a failing sensor, or a problem within the converter itself.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced or fluctuating output from the DC/DC converter, leading to dim lights or slow accessory operation
Battery warning light or charging system message on the dashboard
Electrical accessories such as infotainment or climate control behaving erratically
In some cases, the vehicle may enter a reduced power mode or fail to start due to a discharged auxiliary battery

Common causes, most likely first

Faulty voltage sensor on the DC/DC converter circuit
Damaged or corroded wiring or connector at the sensor or converter
High resistance in the sensor ground circuit
Internal failure within the DC/DC converter affecting sensor output
Poor connection at the powertrain control module connector
Software calibration issue in the control module (less common)

How to diagnose and fix it

Perform a visual inspection of the sensor wiring and connectors for damage or corrosion
Use a scan tool to check for related codes and freeze-frame data to confirm the fault conditions
Measure sensor reference voltage and ground at the sensor connector with a multimeter
Check resistance and continuity of the signal circuit between the sensor and the control module
Compare sensor live data against actual converter output using a known-good meter
If wiring and sensor test good, follow the manufacturer's diagnostic flow for converter internal faults
Replace the faulty sensor or converter as indicated by test results, then clear codes and verify repair

When the sensor is not the real culprit

A low voltage sensor reading often results from a poor ground connection rather than a failed sensor, so always load-test the ground circuit before condemning parts.
The DC/DC converter on hybrid and electric vehicles may set this code due to a low auxiliary battery, which can mimic a sensor fault and lead to unnecessary replacement.
Corrosion inside a connector can cause intermittent low signals that only appear under certain temperature or vibration conditions, so wiggle-test wiring while monitoring live data.
Some vehicles require a software update to the control module to correct overly sensitive thresholds for this code, so check for technical service bulletins before diagnosing hardware.
This code can be set by a failing 12-volt battery that drags down the converter output, so always verify battery health and charging system operation first.

Can I keep driving with P0E38?

You can usually drive with this code if the vehicle runs normally, but avoid relying on electrical accessories for long periods and do not ignore a battery warning light. If the vehicle enters reduced power mode or the battery drains, stop driving and seek professional diagnosis to prevent being stranded.

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.