Powertrain, generic · Hybrid propulsion

P0A0D High Voltage System Interlock Circuit A High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

The voltage sensed on interlock loop A is higher than expected – most often a short to a voltage source, or the loop not being pulled down when the module expects it. GM checks both states: in the 2016 HPC2 table P0A0D sets when the sensed voltage exceeds 24 % of 5 V with the source switched off (5 of 8 samples) or 44 % with it switched on (4 of 6 samples), Type A with MIL after one trip. Hyundai's Sonata Hybrid 2011-2015 bulletins send P0A0D straight to the HEV safety plug, alongside high-voltage path and relay codes, with check engine light and no ready mode. Mercedes model line 243 stores P0A0D00 in the battery management as a short to positive. P0A0C is the low-side counterpart; both leave the HV system switched off.

Likely causes

Service/safety plug not fully inserted or with poor contact (Hyundai Sonata Hybrid)
Interlock wire shorted to a 12 V or reference voltage
Damaged interlock harness or connector after body or battery work
Faulty interlock stage in the battery or hybrid control module

Symptoms

  • No ready mode or ready light blinking
  • Check engine and charging warning lights on
  • Vehicle cannot be started

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.5–4 h

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

Parts involved

hv interlock loophv service connector

Related codes

P0A0AP0A0BP0A0CP0A0EP0D18

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.