P0A1F on Mercedes-Benz: How to Diagnose & Fix
Motor Generator B - Performance
1 Mercedes-Benz model · 1 documented issue · 1 critical
P0A1F on Mercedes-Benz by model: symptoms, diagnosis and fix
Other control units on the EVA2 bus continuously send diagnostic requests to the high-voltage battery management system. The BMS memory overflows, the module shuts down, and the HV contactors open - disconnecting the 108 kWh pack from the drive unit. The result is an instant loss of propulsion at speed with the red turtle icon on the display, even with a nearly full state of charge. NHTSA recall 24V-372 covered 14,912 EQE/EQS sedans and SUVs, and owners reported the failure occurring on freeways before the fix.
Common Symptoms
- Complete loss of drive power while driving
- Red turtle warning icon on display
- "Electrical system malfunction" message
- Vehicle coasts to a stop with charge remaining in the pack
- Restart required to regain drive
How to Fix
Dealer reflashes the battery management system software under recall 24V-372 (no cost). If loss-of-power events continue after the flash, the shop should check for a weak 12V auxiliary battery and pull HV network fault memory, since a low 12V supply produces the same symptom set.
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Sources for this issue (3)
P0A1F code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0A1F mean on a Mercedes-Benz?
P0A1F stands for "Motor Generator B - Performance." In standard usage this hybrid code corresponds to 'Battery Energy Control Module Performance,' meaning the module that manages the high-voltage battery failed an internal performance or self-test check. This control module monitors the hybrid battery pack's charge, temperature, and cooling, and runs internal integrity checks on its own memory and processing. When those checks don't meet specification, the code is set, and it usually points to an internal module fault rather than the battery cells themselves. Expect a hybrid warning light and possibly reduced electric assist or readiness. On Mercedes-Benz it is documented across 1 model: EQS SUV.
What are the most common causes of P0A1F?
The most common causes of P0A1F are: Internal fault within the battery energy control module, Software/calibration corruption in the module, Damaged wiring or connectors at the module, Poor power or ground supply to the module, Low 12V (auxiliary) battery voltage, Moisture/corrosion intrusion at the module, Faulty hybrid battery pack sensor inputs. The specific cause varies by vehicle.
How much does it cost to fix P0A1F on a Mercedes-Benz?
Repair costs vary widely with the root cause and Mercedes-Benz model; each issue on this page carries its own estimate where one is published.
Looking for P0A1F on a different make?
View P0A1F across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.