Hill Descent Control (HDC) HDC Relay

Hill Descent Control (HDC) HDC Relay

The HDC relay (C0575) is located in the engine compartment fuse box, and is provided a feed by the ABS ECU (C0500) on a BR wire. Operation of the HDC relay is controlled by the ABS ECU via the HDC switch (C0365 on manual vehicles, C0878 on automatic vehicles) on a W wire (see below).

When energised, the HDC relay (C0570) provides a feed to the following on GP wires:

The ABS ECU (C0500). The LH brake lamp (C0121). The RH brake lamp (C0125). The CHMSL (C0613).

HDC Switch (Manual Transmission) The HDC switch (C0365) is mounted on the gear lever, and informs the ABS ECU (C0500) when HDC has been selected. When HDC is selected, the switch contacts close, and a feed is provided to the ABS ECU on a PS wire.

HDC Switch (Automatic Transmission) The HDC switch (C0878) is mounted on the centre console, and informs the ABS ECU (C0500) when HDC has been selected. When HDC is selected, the switch contacts close, and a feed is provided to the ABS ECU (C0500) on a PS wire.

NOTE: The ABS ECU will only initiate HDC if either 1st or reverse gear are selected, and brake temperature doesn't exceed 400 ° °

C (752 F).

For more information on HDC, refer to the Brakes section of the System Description and Operation Workshop manual.

Diagnostic Socket

The diagnostic socket (C0040) is connected to the ABS ECU (C0500) by a K wire, enabling the ABS ECU to be interrogated by TestBook or T4.