Powertrain, generic

P0E39 DC/DC Converter Voltage Sensor B High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P0E39 reports that sensor B of the DC/DC converter reads far too high, a pattern GM attributes to a short to battery. The 2025 engine tables (25OBDG03A) set the bar at more than 28 V for raw voltage value 2, again needing 320 failing samples within 400 at 12.5 ms and a battery voltage of at least 6.6 V, with Type B confirmation over two trips. If only sensor B shows the excess while sensor A and the ECM's own run/crank reading stay normal, a wiring fault on the B path is far more likely than a converter that really puts out such a voltage. A lost reference ground can also let the signal float upward. Sensor A's high code is P0E34; a low reading on sensor B is P0E38, an implausible but valid one P0E37.

Likely causes

Sensor B signal shorted to a voltage-carrying wire
Open reference ground letting the signal float high
Failed measuring circuit for sensor B

Symptoms

  • MIL on after two trips (GM)
  • Start-stop switched off

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

dcdc voltage sensor bwiring harnessdcdc converter

Related codes

P0E34P0E36P0E37P0E38P0E3A

References: gsi.ext.gm.com, law.cornell.edu.