Suzuki Jimny MB91F062BS Mileage Correction by iProg Clone

Suzuki Jimny 2018/2019 mileage data is stored in the Fujitsu MB91F062BS mcu rather than eeprom 93c** chip. iProg clone is the least expensive device to correct mileage on this model.


Original KM: 45,000 km

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European panel Suzuki 34110-78RA0

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Test connection with expected errors


Disassemble the instrument cluster

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It turned out that the cluster uses a microcontroller (MCU) – Fujitsu MB91F062BS.

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MCU Fujitsu MB91F062BS + pins for connecting the programmer are visible on the left
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Close-up connection pins (we do not pay attention to this microcircuit)

This means that there is no separate EEPROM chip and the data must be read directly from the MCU. It has 2 memory zones:
– Workflash (64kb) – EEPROM emulation
– Mainflash (1Mb) – The firmware itself



Mileage correction plan

1. Take the dumps from the cluster
2. Contact expert for services on the necessary dump edits.
3. Write back


Now for the steps.

1. I ordered the Chinese version of the iProg + programmer. Looking ahead – reading / writing Workflash is excellent.

At the same time I found out that there are options with MB91F061BS – almost the same MCU but 512kb Mainflash instead of 1Mb on * 062BS .

I crossed my fingers and ordered the iprog programmer, which surprisingly came from a local warehouse in 2 days. I prepared a virtual machine with Windows 7 (later I borrowed a laptop with W10 from a friend) and set up the software. Light flour was to find iProg with working scripts for the Chinese. the kit included a disk that had nowhere to insert in 2023, but a little later the seller answered and gave a link to download from Mega, but by that time I had already found another working version.

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The insides of the programmer

Connecting the device to the programmer

In my case, I just took the references from wiring diagram and played it on the table, referring to the schematic for this MCU in iProg

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Scheme from iProg
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Soldering to the dash
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Used adapter with simple connector pinout

Next comes the successful draining of the original dumps and their backup in case you need to fill in everything as it was.

Power connection on the table

Here I am attaching a power supply connection diagram for the cluster on the table, regarding the CAN pins, I called them on the board from the microcircuit that works with CAN, according to the datasheet, it’s better to double-check, but everything seems to be correct.
For power – be sure to connect both GNDs.

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Jimny JB74 Denso dash pinout


Additional training

In the back of the Internet, 2 other variants of Workflash dumps were found so that there was something to start the comparison with.
1 – EU (like Portuguese) with all the errors as in mine
2 – Japanese without radar errors, without TPMS, oil, etc.


Brief summary

In fact, the results are not expected for a long time, but from what I could break. Everything described below concerns only Workflash so far :
– All dumps in HEX form are 95% different, but have the same division in addressing.
For example:
– It was possible to turn off the oil indicator light in the EU dump by zeroing blocks C30E-C33B . The most useless information, and with further attempts to decompile in IDA Pro, the assembler code in this place did not prompt me to any thoughts, but I’m zero in the assembler and the decompilation is not sure that it was correct.
– I tried to clean the firmware completely. Then the cluster rolls into the Japanese version, without errors, but without the rest of the functionality.

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– I tried to clean everything a little bit, and as a result, one firmware with cleaned module works like European until the last one, however, when the last DAC0 module is changed , it switches to Japanese. This generally makes me think that to disable errors in the European version, you need to edit Mainflash and not Workflash.
— At some point, I thought that I won, I got a European cluster but without errors, like the Japanese version. The joy was short-lived, it turned out that I just got all the Japanese stripped down without errors but with English, although everything is reset to Japanese if you throw it into defaults from the cluster menu.

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I wanted to try playing with Mainflash using iprog+. when trying to record, it crashes with an error at the zeroing stage, and I even thought that the games ended when it erased 20% of Mainflash and the cluster no longer turned on. But then it turned out that if you click on the record 100 times, then it falls but advances in zeroing, and then it correctly writes everything from the file to Mainflash.