When a BMW CAS3++ module is left corrupted after an unsuccessful ISTA-P programming attempt, the vehicle may no longer start because the rolling codes between the CAS and DME are no longer matched. In this case, the Xhorse VVDI Key Tool MIDI can repair the CAS using its ISTAP repair function.
Why the CAS Needs Repair
The problem started after the CAS module was programmed with ISTA-P. After the failed programming, the vehicle would no longer start.
ISTA showed an EVS-related synchronization and communication problem between the CAS and DME, indicating that the required data exchange between the two modules was no longer correct.
The repair approach was to first restore a clean CAS EEPROM dump containing the vehicle’s ISN and VIN data, then use the ISTAP repair function on the CAS.
Prepare the CAS
- Read the CAS EEPROM with VVDI PROG
Use VVDI PROG to read the CAS EEPROM and prepare a clean dump containing the vehicle’s ISN and VIN data.
- Write the clean EEPROM dump back
Write the prepared EEPROM dump back to the CAS module. The ZB number shown on the CAS module was 9278746.
Run ISTAP Repair
- Turn on the power supply and connect the CAS module. Insert the key into the ignition and follow the device prompts.
- On theKey Tool MIDI, follow the complete path:Immo Programming → BMW → Select from system → CAS3/CAS3+ immo system → ISTAP repair → Start programming → Use the known CAS series number to repair, the value can be obtained by “Vehicle Information” function → CAS ID: 9278746
- Follow the prompts and press OK. The device then erases the flash and performs the programming. The repair took around 5 minutes in this case.
Check ISTAP Repair Compatibility
ISTAP repair does not support every CAS part number or software version. The tested information was as follows:
- The tested CAS used SW 22.5, and the repair was successful.
- Newer versions around SW 21 and above were found suitable in this test.
- Older versions such as SW 12.5 may not be supported, depending on the CAS part number.
- Other tested part numbers, including 9237046 and 9226238, were not confirmed for this repair.
The CAS information also shows the hardware, software, diagnostic, and index versions. The tested module used C4 hardware.
Check for EEPROM Problems
The Key Tool MIDI may also report an EEPROM or key-file problem during other operations, such as uploading the EEPROM, making a dealer key, or running a signature check.
If the EEPROM data has been corrupted during programming with ISTA or KFP, the EEPROM repair function may be required before continuing with the related operation.
Reinstall the Repaired CAS
After the ISTAP repair is finished, reinstall the repaired CAS module in the vehicle. The key had already been generated with the Key Tool MIDI and stored in slot 1.
The repaired CAS was reinstalled, the vehicle started normally, and the basic vehicle functions were working.