P0A0CHigh Voltage System Interlock Circuit A Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- The voltage sensed on interlock loop A is too low while the module drives the loop – typically an opened loop or a short to ground. GM documents it codegenau: in its 2016 HPC2 table P0A0C sets when the sensed interlock voltage stays below 30 % of the 5 V test signal in 2 of 2 samples (12.5 ms each) with the 12 V supply above 10.2 V; it is Type A, so the MIL lights after one trip. The 2011 Volt tables used a 10 % threshold. Mercedes-Benz model line 243 stores P0A0C00 in the DC converter and on-board charger as a short to ground in the interlock circuit. The opposite fault is P0A0D. Since the loop guards against live HV parts, the system drops the contactors and the car will not drive on electric power.
- What you may notice
- Check engine light (GM Type A) and hybrid/EV warning
- No ready mode, electric drive unavailable
- Charging may be blocked
- Likely causes
- LikelyHV connector, cover or service disconnect open, interrupting the loop
- PossibleInterlock wire shorted to ground, e.g. chafed at a module or the body
- PossibleCorroded or pushed-back interlock pins
- RareFaulty interlock source or sense stage in the battery or hybrid module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.