What it means
The ECM detects a low fault on the dc/dc converter voltage sensor b. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
DC/DC converter voltage sensor B measures a voltage used by the control module to assess converter operation. P0E38 sets when sensor B's signal falls below the expected range, which can happen if the signal is pulled toward ground or the sensor is internally shorted.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
Symptoms
- Hybrid/EV system warning light may turn on
- Reduced power or charging performance
How to diagnose it
- Check freeze-frame and live data to confirm sensor B is reading low, and compare it with sensor A and other available converter voltage readings.
- With the system safely powered down, inspect sensor B's signal wire and connector for chafing, trapped wiring, corrosion, or contact with ground.
- Using the manufacturer's wiring diagram, test the sensor B signal for an unintended ground and check its power and ground circuits.
- If the harness is not shorted, test sensor B according to the manufacturer's procedure to determine whether its internal signal is low.
- After repairing the short or replacing a confirmed failed sensor, clear the code and confirm the signal responds plausibly.
Common fixes
- Repair chafed or pinched sensor B signal wiring that is touching ground.
- Clean or repair corroded or damaged terminals at the sensor B connector.
- Restore a faulty sensor B power or ground connection.
- Replace voltage sensor B if its signal remains low with a sound harness.
Can I keep driving?
A low sensor B signal can lead to reduced power or charging performance. Keep driving to a minimum and stop safely if the vehicle loses power or displays a hybrid/EV warning.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.