P2AD4Intermediate System Voltage Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2AD4 reports that the voltage of an intermediate system, a supply level between the 12 V network and a high-voltage traction battery, has fallen below its lower limit. In practice this describes 48 V networks of mild hybrids, which carry a belt or integrated starter-generator and loads such as electric compressors; German makers agreed on such a level in 2011, and Audi and Mercedes-Benz use it since 2018. No manufacturer publicly documents P2AD4, so the exact meaning (which module measures, which threshold) remains maker specific. Plausible causes are a weak or deeply discharged 48 V battery, a DC/DC converter that drains the network, poor connections or a starter-generator that does not charge. CARB treats hybrid components in (f)(15.2.3) but grants mild-hybrid exemptions. Drivers lose start-stop and boost assistance.
- What you may notice
- Warning lamp or message about the electrical system
- Start-stop and electric boost unavailable
- Engine may not restart via the starter-generator
- Likely causes
- LikelyWeak or deeply discharged 48 V battery
- PossibleStarter-generator not charging the intermediate network
- PossibleDC/DC converter drawing the network down
- RareLoose or corroded high-current connection
- 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: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.