Start stop memory

[vcosta]

Recently acquired a Seat Leon MK4 2021, having same problem as anybody else with Start and stop resetting each time I turn off the car.

Looked in other threads, other forums, youtube, etc, and can't find any specific feedback for this model. Only option without hardware is the option of disabling the BMS of the battery, but that doesnt seem to be a good solution, as can bring other problems. Regarding the other option, with a module (hardware) from ali.express, Im afraid to use it and what it can cause.

Whats your feeback?

 

[smiffypr]

You need to set the flag in the HVAC module that tells the engine to keep running.

 

[vcosta]

You need to set the flag in the HVAC module that tells the engine to keep running.

Can you detail a bit more? Or provide a tutorial? Already ordered obdeleven but hasnt started coding yet, dont know how it works. Ty

 

[smiffypr]

Once you have the DBD tool, go into the HVAC module and look for a setting that says something like "Tell engine to keep running". Really it is as simple as that. The precise steps you go through will depend on the OBD tool and probably the software on your HVAC module. NOTE that if you turn the "Clima" off, the engine will not be sent the signal to keep running.

 

[vcosta]

Once you have the DBD tool, go into the HVAC module and look for a setting that says something like "Tell engine to keep running". Really it is as simple as that. The precise steps you go through will depend on the OBD tool and probably the software on your HVAC module. NOTE that if you turn the "Clima" off, the engine will not be sent the signal to keep running.

I dont really like that option, and its not even definitive

 

[TVK]

MK4 Can't be coded. Trick with coding works on a mk3.
Only thing you can do is to place a memory-module.
I got this on mine, and it works great:

Start/stop memory

 

[vcosta]

MK4 Can't be coded. Trick with coding works on a mk3.
Only thing you can do is to place a memory-module.
I got this on mine, and it works great:

Start/stop memory

Yeah, thats what I've investigated. Do you have a Leon mk4? I got similar module from ali but havent tested it yet, Im afraid of the errors.

Also, have you disconnected the battery as they say in the tutorial video? I have read that isnt a good ideia, you should let the car fall asleep and perform the installation instead.

Thanks

 

[smiffypr]

The HVAC flag change works on my 2025 model year Leon, I don't know what MK that is.
If you disconnect the battery, when you connect it back up there will be a few faults which disappear after a few yard of motion.
If you don't disconnect the battery you risk serious damage to all of the modules on the canbus that you disconnect and connect. It is a very small risk but the consequences could be major.

 

[vcosta]

The HVAC flag change works on my 2025 model year Leon, I don't know what MK that is.
If you disconnect the battery, when you connect it back up there will be a few faults which disappear after a few yard of motion.
If you don't disconnect the battery you risk serious damage to all of the modules on the canbus that you disconnect and connect. It is a very small risk but the consequences could be major.

I believe it works, but I dont consider it a good and definitive solution.

Regarding the battery, I agree with you, there are possible concerning consequences, I wonder some commentaries I read somewhere that talk about consequences of disconnecting it.

 

[TVK]

I installed the module on a 2022 Leon KL (Mk4).
AliExpress modules would likely work too, but since the Mk4 is quite sensitive regarding electronics—and to be safe and avoid issues—I opted for one from a reputable company rather than an AliExpress item.

Then there’s the plug on top of the battery.
This plug is for the car's battery monitoring system; the unit measures various parameters.
This system is also required if you have a hybrid version (I drive a 2.0 petrol engine, non-hybrid).
If you disconnect it, the start/stop system indeed stops working, but you get an error message on the dashboard every time you start the car, and stay on the dashboard.
(Been there, done that.)

I tried everything via coding to bypass and disable the start/stop system, but that resulted in errors, dashboard warnings, warning lights staying on, and so on.

The module I mentioned in my previous reply is the only option for disabling the start/stop system.

The only thing you see when starting the car is the message: "Start/stop system disabled."
You see this message just once, and then it disappears.

So, to reiterate: you CANNOT disable or manipulate the start/stop system on the Mk4—or any car built after 2020—via software coding.