P2BC4 code meaning
Battery Charging System Positive Contactor B Circuit
What P2BC4 means
P2BC4 is the catch-all electrical code for positive contactor B of the charging system, the second charging switch on the plus side next to contactor A (P0D07). Which charging path B serves is up to the maker: Mercedes-Benz files its B codes under the DC charge connection unit of its plug-in hybrids, EQB and eSprinter, Mazda under the on-board charger branch of its two large plug-in SUVs, and Audi calls it charging contactor 2 on the Q8 e-tron. No manufacturer documents P2BC4 itself publicly. Under CARB the charging system of plug-in vehicles has to be supervised, and a GM patent judges such contactors by their coil current. Fused or non-closing contacts are P2BC5/P2BC6, driver faults P2BC7–P2BCA, the minus side P2BCB. Usually only the affected charging mode is lost.
P2BC4 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2BC4
- DC fast charging or on-board charger charging (depending on design) refused
- Charging fault message in the cluster or app
- Driving usually still possible
Common causes of P2BC4
- PossibleCoil of positive contactor B open or shorted
- PossibleWiring or connector fault in the contactor B branch
- Less likelyFault or software issue in the controlling module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bcs pos contactor bWiring harnessBms
What each part of P2BC4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| B | Area: hybrid propulsion. |
| C4 | The exact fault in that area. |
What to do next
- Note P2BC4 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 P2BC4
What does P2BC4 mean?
P2BC4 means "Battery Charging System Positive Contactor B Circuit". P2BC4 is the catch-all electrical code for positive contactor B of the charging system, the second charging switch on the plus side next to contactor A (P0D07). It is a generic code, so it means the same on every make.
Is it safe to drive with P2BC4?
P2BC4 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2BC4 fail an emissions test?
P2BC4 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 P2BC4 to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P2BC4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.