The Expert Guide to Clearing Crash Data and Re-Validating BMW SME Modules.
This is an advanced, expert-level guide that details the complete process for clearing "crash data" from a BMW High-Voltage Battery Management unit (SME / HVS_01) and re-validating it for use. This procedure is necessary after a vehicle has been in an accident, which typically logs the permanent fault code 21F37E.
The Problem: "Crash Data" Lock
After even a minor accident, the Airbag Control Module (ACSM) can trigger a safety protocol in the SME, permanently locking the high-voltage battery. This logs the fault code 21F37E - Impact detection: Crash detected due to ACSM signal. Once this flag is set, the battery will not charge or discharge, rendering the vehicle unusable until the SME is reset.
CRITICAL SAFETY WARNING
This entire procedure involves working with high-voltage battery systems and advanced diagnostic software. It is EXTREMELY DANGEROUS and should only be performed by certified high-voltage technicians with professional training. An error can result in fatal electric shock, fire, or explosion. Proceed at your own absolute risk.
The Reset & Validation Procedure
The process is divided into two main phases: validating the SME certificates with an engineering tool like E-Sys, and then restoring cell data using ISTA.
Phase 1: Certificate Validation (E-Sys)
The first step is to "virginize" the SME by restoring its security certificates. This process will take the module from an "EMPTY" state to an "OK" state.
1. Connect to the vehicle with E-Sys and navigate to the "Certificate Management" section for the SME module.
2. Use the function to "Create CBB Request File". This reads the unique data from your SME.
3. Use the provided solution files (CBB Response File) with the "Write data" function to upload the new certificate data back to the SME.
4. Before writing the new data, the certificate status will likely show as EMPTY, as seen below.
5. After you write the CBB Response File, the certificate status should change to OK. Use the "Check data" function to confirm this. This "OK" status means the SME is now successfully validated and ready for the next phase.
Phase 2: Restore Cell History (ISTA)
Now that the SME is validated, you must restore the battery cell history using ISTA to make it fully operational.
1. Close E-Sys and connect to the car with ISTA. Clear any existing fault codes in the fault memory.
2. Go to "Vehicle management" -> "Service functions" and find and select the following service plan: SME, control unit exchange: Restore the history of the cell modules from the partner control unit.
3. Execute this service function and follow all on-screen instructions carefully. ISTA will run a comparison between the EME and SME, reset the SME, and write the cell history.
Phase 3: Finalization
- Once the ISTA service function is complete ("The counters for the reuse of the cell modules were read out from the EME and written in the SME"), close the service plan.
- Perform a final "Delete fault memories" scan to clear all remaining errors.
- The crash data error will be gone, and the car will be ready.
The Core Logic (Important Note)
The principle of this method is: Validate with original "eeprom" data, save the file, then reset and write the "validated" file back to the SME. It is highly recommended to save the new, validated EEPROM file. This file will be needed if you ever update the vehicle's software in the future, otherwise you may encounter a validation error again. This method allows the SME to be installed on any compatible car, regardless of the original model.
System Requirements & Testing
- Operating System: The diagnostic software required for this procedure (E-Sys, ISTA) is Windows-based and has been tested on Windows 10 LTSC 2019.
- Required Hardware: An ENET Cable or ICOM interface.
- Required Software: BMW E-Sys and ISTA.
