Powertrain, generic (extended)

P2AD4 Intermediate System Voltage Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Weak or deeply discharged 48 V battery
Starter-generator not charging the intermediate network
DC/DC converter drawing the network down
Loose or corroded high-current connection

Symptoms

  • Warning lamp or message about the electrical system
  • Start-stop and electric boost unavailable
  • Engine may not restart via the starter-generator

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time1–6 h

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

Parts involved

dc dc converterstarter generatorwiring harness

Related codes

P2AD5P0562P0A94

References: law.cornell.edu, en.wikipedia.org.