P0A0BHigh Voltage System Interlock Circuit A Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Vehicle cannot be started
- High-voltage system warning in the instrument cluster
- Several modules store interlock codes at the same time
- Likely causes
- 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
- RareFaulty interlock driver or receiver in a control module
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.