ABS Modulator

BRAKES

DESCRIPTION AND OPERATION

70-23

The following table describes the warning lamps, their associated faults and system response.

ABS Modulator
The ABS modulator controls the supply of hydraulic pressure to the brakes in response to inputs from the ABS ECU. 
The modulator is attached by three mounting bushes to a bracket on the LH inner wing, and connected to the primary 
and secondary hydraulic circuits downstream of the master cylinder assembly. Two electrical connectors link the ABS 
modulator to the vehicle wiring. Internal passages in the ABS modulator, separated into primary and secondary 
circuits, connect to the various components that control the supply of hydraulic pressure to the brakes. Valves and 
check valves control the flow through the internal circuits. A damper chamber and restrictor are included in each circuit 
to refine system operation. Inlet and outlet solenoid valves control the flow to the individual brakes. An expansion 
chamber is connected to each circuit to absorb pressure. A return pump is connected to both circuits to provide a 
pressure source.

System Status

Hand 

Brake 

Warning 

Lamp

Brake 

Warning 

Lamp

ABS 

Lamp

DSC Lamp

HDC 

Lamp

Message Centre

Lamp check

On for 2 

seconds

Amber for 

1 second 

then red 

for 1 

second

On for 2 

seconds

On for 2 

seconds

On for 2 

seconds

ECU under voltage

On, red 

and amber

On

On

Off

Hand brake On

On, red

Release park 
brake (when 
driving)

Low brake fluid level

On, red

Check brake fluid

Electric Brake Assist (EBA) 

failure) ABS & EBD available)

On, amber

Off

ABS Failure (EBD available)

On, amber

On

On

Off

EBD failure

On, red

On

On

Off

DSC failure

On, 

amber, or 

red

On

On

Single gong 1st 
time failure occurs

HDC failure

On, amber 

or red

On

Off

HDC Inactive

DSC activity (including engine 

intervention)

flash 2 Hz

ETC activity (brakes only)

DSC switched passive (TC 

function still available)

On

ETC activity while DSC 

switched passive

On

HDC switched on (not enabled 

or fading out)

flash 2 Hz

HDC switched on and enabled

On

HDC temporarily unavailable 

(brake overheat)

Off

HDC temp. Not 
available

HDC switching off (due to high 

speed in high range)

Off

No HDC - slow 
down

Driver attempt to switch on 

HDC at high speed in high 

range 

Off

No HDC - slow 
down