BMW Siemens MS43 · MS43X-Custom-Firmware (ms4x)
Live Map Switch
Three calibration sets, switched on the fly from the cruise „+" button
- Choose ECU
- Check file
- Pay
- Download
What the patch does
The same three-slot patch as the well-known MS43X switch, but switched on the fly: the cruise „+" button (with cruise control off) opens a small menu after a short hold, „+" and „−" pick the slot, and the tachometer needle shows the chosen slot (1000 / 2000 / 3000). The change is only applied when you lift off the throttle, so there is no load step. Slot 1 stays untouched — exactly the calibration the file arrived with, your risk-free way back. Slots 2 and 3 start as copies of it and are calibrated by you in TunerPro.
The three slots
Stock / fallback
Unchanged: the calibration you uploaded. After flashing, the car drives exactly as it did before.
Stage 1
Starts as a copy of slot 1. Your everyday setting — ignition, lambda, boost and limiter all freely calibratable.
Stage 2
A second free set. Typically for E85, track use, or a valet setting with reduced power.
Switchable per slot
- Full-load ignition — RON98 and E85 separately
- Lambda/AFR targets — RON98 and E85 separately
- VANOS targets, intake and exhaust
- Boost: target (RON98/E85), pilot PWM, fixed PWM
- Launch control: on/off, rpm, ignition offset, AFR target
- Rolling antilag: ignition offset for RON98 and E85
- Overboost and scramble boost: threshold, hysteresis, offset
- Rev limiter including hysteresis
- Idle speed — standard, driving, A/C, driving + A/C
- Overrun cut: cut-off rpm, antilag rpm, minimum ignition
- Injection time correction curve
What you need
- Original files only, exactly as the ECU left the factory: no tuning and no added patches (for example launch control, ignition cut or pops code). EWS-off is allowed.
- It must be a fresh full read from your own car, complete and including the bootloader section. A partial read without that section is not enough.
- No bins from the internet. Files from MS4X, forums, collections or file swaps are not supported — they come from a different vehicle, are often already modified, and will not work on your ECU.
- An MS4x tool to correct the checksum and write the full flash — the shop deliberately does not calculate the checksum.
- TunerPro to calibrate slots 2 and 3.
Specifications
Questions about this product
How do I switch while driving?
With cruise control off, hold the „+" button on the wheel for about two seconds — the tachometer needle jumps to the current slot, showing the menu is open. Tap „+" and „−" briefly to pick the slot (the needle follows: 1000 = slot 1, 2000 = slot 2, 3000 = slot 3). Holding „+" for about a second confirms and closes the menu; after a few seconds without input it closes without changing anything. The change is applied smoothly on your next throttle lift-off, with no load step. Hold times and thresholds are parameters in the XDF.
What is the difference to the pedal map switch?
The switchable content is the same — the same three slots with ignition, lambda, VANOS, boost, launch control, no-lift-shift and limiter per slot. Only the operation differs: here you switch while driving through a menu on the cruise „+" button, instead of using the brake and throttle while stationary.
Does it interfere with the cruise control?
No. The menu only responds while cruise control is OFF. As soon as cruise is on, the buttons do their normal cruise job and the menu is locked out.
Why is the change only applied on throttle lift-off?
So the calibration never switches in the middle of load. You pick the slot in the menu, and the moment you lift off the throttle the ECU takes it — smoothly and with no noticeable step.
Why does slot 1 stay unchanged?
So there is always a state in which the car runs on exactly the calibration it had before flashing. New calibrations belong in slot 2 or 3.
Why does the file have to be stock?
The patch identifies the firmware by fixed byte patterns and writes into areas that are empty in stock files. An existing tune has changed those patterns and may have occupied those areas. The check rejects such files rather than quietly overwriting something — that would be the shortest path to a dead ECU.
Can I pass the file on to a friend?
No. Every file is created for exactly one vehicle and only runs there. A second car needs a second purchase.
Does the shop calculate the checksum?
No, deliberately not. The bin leaves the shop uncorrected; you fix the checksum with the MS4x tool you also flash with.
What does an update cost?
Nothing. Simply upload your bin again: the shop recognises you and releases the download without payment.