P2DB9 code meaning
Battery Charging System B High Voltage Interlock Circuit Low
What P2DB9 means
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.
P2DB9 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2DB9
- Charging through path B not possible
- Charging system warning message
Common causes of P2DB9
- Most likelyInterlock wire chafed through and touching ground
- PossibleWater or dirt in an interlock connector causing leakage to ground
- Less likelyDefective interlock source or measuring stage in the control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bcs b hv interlockWiring harnessOn board charger
What each part of P2DB9 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| B9 | The exact fault in that area. |
What to do next
- Note P2DB9 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2DB9
What does P2DB9 mean?
P2DB9 means "Battery Charging System B High Voltage Interlock Circuit Low". P2DB9 is stored when the sensed voltage of the charging system B interlock loop stays too low. It is a generic code, so it means the same on every make.
Is it safe to drive with P2DB9?
P2DB9 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2DB9 fail an emissions test?
P2DB9 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2DB9 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P2DB9 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.