P0A0B code meaning
High Voltage System Interlock Circuit A Performance
Powertrain system Generic code P0Axx codes Check engine light
What P0A0B means
The interlock loop A responds electrically, but its behaviour does not match what the module expects – for example a loop resistance outside the window, a signal that does not follow the commanded test pattern, or two modules on the same loop disagreeing. Mercedes-Benz logs P0A0B00 in the battery management system, the DC converter and the on-board charger of model line 243 when the vehicle will not start; its listed causes include oxidised interlock pins in the low-voltage connectors, twisted or chafed harnesses and bent pins on HV components. Patent literature explains why voltage-based loops are prone to false alarms from contact resistance and interference. Unlike P0A0C/P0A0D this is not a clear short. Expect the HV system to stay off.
P0A0B at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0A0B
- Vehicle cannot be started
- High-voltage system warning in the instrument cluster
- Several modules store interlock codes at the same time
Common causes of P0A0B
- Most likelyOxidised interlock pins in low-voltage connectors raising loop resistance
- PossibleImproperly connected HV connector or bent interlock pins on an HV component
- PossibleTwisted or chafed interlock harness rubbing on the body
- Less likelyFaulty interlock driver or receiver in a control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv interlock circuit aWiring harnessBms
What each part of P0A0B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A | Area: hybrid propulsion. |
| 0B | The exact fault in that area. |
What to do next
- Note P0A0B 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 P0A0B
What does P0A0B mean?
P0A0B means "High Voltage System Interlock Circuit A Performance". The interlock loop A responds electrically, but its behaviour does not match what the module expects – for example a loop resistance outside the window, a signal that does not follow the commanded test pattern, or two modules on the same loop disagreeing. It is a generic code, so it means the same on every make.
Is it safe to drive with P0A0B?
Drive gently and only to a workshop. With P0A0B the car can go into limp mode (reduced power) to protect itself.
Will P0A0B fail an emissions test?
P0A0B 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 P0A0B to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P0A0B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.