Powertrain, generic · Hybrid propulsion

P0B35 High Voltage Service Disconnect Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B35 sets when the service disconnect detection signal stays below its lower limit. Where the loop is coded with a resistor in the plug, as in a Lear patent, a reading near zero typically points to a short to ground in the loop wiring; the exact meaning depends on how the manufacturer powers the input. Ford traced an intermittent short to ground in the low-voltage interlock wiring as the cause of its open-loop code P0B37 on the C-Max Energi, which shows how chafed harnesses act here. No manufacturer documents P0B35 publicly. CARB treats such signals as monitored hybrid inputs. High, open and performance faults are P0B36, P0B37 and P0B34. The contactors usually stay open.

Likely causes

Detection loop wire chafed and shorted to ground
Moisture or corrosion in the plug base bridging to ground
Coding element in the plug shorted
Battery controller input stage fault

Symptoms

  • No ready mode or stall with a stop-safely message
  • MIL and high-voltage warning on
  • Charging not possible

Repair estimate

DifficultyShop_onlyWorkshop 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 service disconnect switchwiring harnessbms

Related codes

P0B33P0B34P0B36P0B37P0A0C

References: law.cornell.edu, patents.google.com, patents.google.com.