Powertrain, generic (extended)

P2DB9 Battery Charging System B High Voltage Interlock Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2DB9 is stored when the sensed voltage of the charging system B interlock loop stays too low. Since the module feeds a test voltage into the loop, a low reading usually means current is escaping to ground: a chafed wire touching the body, moisture in a connector, or a failing measuring stage inside the module. No manufacturer documents P2DB9 publicly. For the A-side loop of the Chevrolet Volt, GM's 2011 and 2014 tables call the reading faulty when it drops under 30 % of the sourced 5 V in two of two 12.5 ms samples, rated Type A (P0D17); that logic is a fair model for loop B. The high counterpart is P2DBA, a clean open P2DB7. Path B will not be used for charging until the fault is cleared.

Likely causes

Interlock wire chafed through and touching ground
Water or dirt in an interlock connector causing leakage to ground
Defective interlock source or measuring stage in the control module

Symptoms

  • Charging through path B not possible
  • Charging system warning message

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–4 h

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

Parts involved

bcs b hv interlockwiring harnesson board charger

Related codes

P2DB7P2DB8P2DBAP2DBBP0D17

References: gsi.ext.gm.com, gsi.ext.gm.com.