Peugeot 406 (1998) ZF 4HP20 - "Stop Contactor" Fault & Limp Mode - Wiring/Pinout Help Needed

[bmwr80]

Hello everyone,

I am looking for technical assistance regarding a wiring/pinout issue on my 1998 Peugeot 406 (2.0 Petrol). I am stuck with a permanent "Stop Contactor" (Brake Switch) fault in the TCU, causing the transmission to go into Limp Mode (Sport/Snow lights flashing).

Vehicle Specifications:

Car: Peugeot 406 (Year: 1998)

Engine: 2.0 Petrol (Bosch MP5.2 ECU)

Transmission: ZF 4HP20 Automatic

TCU Hardware ID: Bosch 0 260 002 482

The Problem: The TCU keeps throwing a "Stop Contactor" fault. I cannot clear it. The Diagnostic tool shows an incoherence between the main brake switch and the secondary (safety) switch.

What I have checked so far:

The brake pedal has two separate physical switches.

I have tested both switches, and they are mechanically and electrically functional.

I have traced the wiring for the Main Switch: The signal successfully reaches Pin 10 on the TCU connector.

However, I cannot locate where the Secondary Switch connects to the TCU or the ECU. I am unable to find any signal from the second switch at the TCU connector.

My Issue: My version of Diagbox/SEDRE does not show the correct wiring diagram for this specific older model (Pre-mux/Transition era). The schematics I have do not match the car's actual wiring harness.

My Questions:

Does anyone have the correct Pinout for the Bosch 0 260 002 482 TCU?

Does anyone know exactly which Pin on the TCU (or the MP5.2 ECU) receives the signal from the Secondary Brake Switch (Red connector usually)?

Is there a known splice or "Borne Equipotentielle" where this specific line tends to fail?

Any help, correct schematic, or pinout data would be greatly appreciated.

Thank you!

[xantia_v6]

Are you sure that the transmission is a ZF 4HP20, not a Siemens AL4? I have not heard of a 4HP20 fitted to a 2.0 petrol. Which version of 2.0 engine is it?

It is typical for these transmissions that when with the diagnostic connected, you must keep your foot on the brake, or they will throw a permanent error code.

The second contact on the brake switch may just be for the cruise control.

Some 4HP20 installations had a hydraulic pressure switch on the brake line so that the TCU could detect heavy braking, but that was later deleted.