P0E99DC/DC Converter Voltage Sensor C Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- With P0E99 the controller finds the voltage sensor C reading of a DC/DC converter pinned near its upper limit. That points to the signal touching a battery feed or reference supply, or to a broken sensor ground that lets the input float up, rather than to a real converter overvoltage. No manufacturer documents P0E99 publicly. For channels A and B GM's 2025 engine tables (25OBDG03A) use more than 28 V as the limit for a 12 V converter, far beyond any genuine output, and confirm P0E34 or P0E39 after 320 of 400 failed samples as Type B. CARB demands such out-of-range checks. Comparing sensor C with the other channels and the battery voltage quickly separates a wiring fault from a converter problem; low readings are P0E98.
- What you may notice
- MIL and charging or 12 V warning possible
- Converter limits or stops its output
- Start-stop function unavailable
- Likely causes
- LikelySensor C signal shorted to battery voltage or reference supply
- PossibleOpen sensor ground letting the signal float high
- RareActual overvoltage from a faulty converter regulation
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.