[MaseratiByChance]

• The warning light comes on EXACTLY 10 seconds after releasing the brake pedal.
• The warning light stays on.
• When the brake pedal is pushed, the light goes out after approximately 0.5 seconds.
• Release the pedal, and 10 seconds later, the light comes on again and stays on.

Additional observation: When I disconnect BOTH rear light clusters, the error is gone and doesn't come back. Disconnect only one, and the error remains, regardless of which one is disconnected. Taillights are original like the streetcar, but only the outer ones are used. The inner ones are disconnected and only there for esthetics.

The most intriguing thing here is the exact 10 seconds it takes every time before the error starts after releasing the pedal. So, I think there must be some kind of checking procedure the TCU is doing that takes exactly 10 seconds.

Can anybody provide insight into what could be the reason? What is measured or checked by the TCU? What takes 10 seconds?

This may sound lame but try replacing all your tail/brake lamp bulbs with the OEM parts. Could be the bulb resistance is higher or lower on one of them causing the fault.

 

[MaseratiByChance]

The car uses the standard light clusters with the leds. So no bulbs to replace.
I measured the current through the switch in several situations.

• 970 mA when both taillights are connected.
• 520 mA when left light is disconnected. So that’s the right taillight + TCU
• 450 mA when right light is disconnected. So that’s te left twilight +TCU
• 1mA when both are disconnected. So that’s only the TCU

Is there another similar vehicle that you could use to measure the current or do a swap? Is there a number you could call to speak with a tech/engineer to ask about the resistance/current through the lamps?

Thinking outside the box, measure the resistance of each lamp and replace the lamps with a resistor of each value to see if that fixes the problem. Should not be to difficult. Determine the brake circuit and ground and insert a modified resistor attached to a similar terminal. For example, put a 26 ohm resistor across both lamps (lamps disconnected), the try putting a 23 ohm resistor across the lamps.

I think the current/resistance should be equal but don't know for sure. In every day vehicles when a bulb burns out or has a higher resistance that will turn on a warning lamp.

 

[MaseratiByChance]

Thanks for all the input.

But I think I’ve solved the issue!!

I was thinking it could be some kind of noise on the wires, when the wires aren’t connected. The tcu sees this noise and triggers the error.

so I put a 2K Ohm resitor parallel with the switch. This way there is a minuscule current of 6 mA constantly flowing, getting rid of the noise.
While braking the resistor is shorted and thus eliminated.

this current is to low to light the brake light or to be seen by the tcu.

I’ve tested it in real life and everything seems to work now as it should.🥳🤩🥳.


What do you all think? Is this a good solution? Should i implement this resistor permanently?

I still of the mind it has something to do with the resistance of the brake lamps. One or the other may have too high or low value. They should be of equal value. But glad you stopped the warning lamp from coming on.