Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Software Downloads On The Most Network
The concept for downloading software is the same as for the CAN network. The CAN uses a PBL (primary boot loader) which is permanently installed in the control module, and a secondary program loading file (SBL - secondary boot loader) which is downloaded into a RAM while the control module is being programmed.
When downloading software for the MOST control modules, a third type of download module is used, GBL (Gateway boot loader). For downloads to the MOST control modules to work, the GBL must be loaded into the infotainment control module (ICM). SBL is used to program the infotainment control module (ICM), in the same way as for all other CAN control modules.
GBL downloading
A PROG command is transmitted on the CAN network to all control modules including the infotainment control module (ICM). This command sets all the control modules to reset mode. Before the infotainment control module (ICM) switches to reset mode, it switches off the light to all MOST control modules.
The PROG command sets all CAN control modules to programming mode. The MOST network is inactive during this phase.
The GBL is then downloaded to a RAM memory in the infotainment control module (ICM). The GBL is then activated and the infotainment control module (ICM) transmits light pulses on the MOST network. The GBL now functions as a connection between the CAN and MOST networks. The GBL sets the MOST control modules to programming mode. All the control modules on the MOST and CAN networks can then be addressed in the same way to download software.
In the event of a total software reload for the control modules on the MOST network, select the MOST network option. Select CAN network for control modules on the controller area network (CAN).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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