ABS/TRACS - Diagnostics and Improvements: Overview
SECTION5
GROUP
59
NO.
801
DATE
Mar. 1996
1996 ABS/TRACS Diagnostics 800 M/Y 1996
REFERENCE: SECTION 5, BRAKES (INCL. ABS AND TRACS); 850 1996-
1996 ABS/TRACS Diagnostics
ABS Mk 20 with an integral Electronic Brake force Distribution (EBD) function has replaced the earlier ABS Mk IV system and the reducing valve for the rear breaks. As before, TRACS is available as a factory option.
Among other advantages, the new ABS system offers:
^ Improved and more precise utilization of rear braking force using the EBD function. This means that rear braking force can be increased under normal braking conditions and that a higher braking force can be applied to the rear wheels when the car is heavily loaded, to help balance brake wear.
^ Quieter operation due to the new design.
^ Lower weight and fewer components.
ABS Mark 20 is an electronic control system which is mainly designed to control the hydraulic pressure in the braking system to help prevent the wheels locking when braking. By stopping the wheels from locking, the ABS system helps prevent loss of control of the car's steering and transmits as much braking effort to the road as possible.
TRACS is an anti-wheel slip system integral to the ABS system. TRACS distributes power between the driving wheels so that most power goes to the wheel with the best grip. The system is mainly designed to help when pulling away on slippery surfaces at up to around 40 km/h (25 mph).
TRACS switches on every time ignition is switched on; it can also be switched on and off via a switch by the instrument panel.
ABS/TRACS Noise Diagnostics
IB1
Begin fault-tracing structure "A" in service manual: Brakes (incl. ABS and TRACS), 850 1996-.
IB2
Check that self test function is operating normally. The system performs a self-diagnostic test when the vehicle reaches a speed of approx. 12 mph. If noise in this speed range is not the usual self-test noise, go to IB5.
IB3
The ABS may cycle when brakes are applied on rough roads or on an incline while making a short turn (refer to IB7 also).
If the brake pedal is applied while the vehicle is driven over uneven road surface, the ABS may cycle and the driver may sense a pulsation in the brake pedal, accompanied by a slight up and down movement of the pedal height and a clicking sound.
This may also happen while driving up an inclined surface such as a driveway while making a sharp turn. Both these concerns represent normal operation of the Anti-Lock Braking System.
IB4
The ABS system helps improve vehicle control (stopping and steering) during severe braking conditions by limiting, brake lock-up, when the system "senses" impending lock-up, braking pressure is automatically modulated in order to help prevent lock-up, which could lead to a skid.
If the ABS operation works normally, no further action is needed. If the system is not functioning correctly, refer to the service manual: Brakes (incl. ABS and TRACS) 850 1996- for further diagnostic information.
IB5
Remove the fuse box cover and inspect for green marking as illustrated under Electrical distribution unit, overview. If marking is present, refer to service manual:
Brakes (incl. ABS and TRACS) 850 1996- for further diagnostic information.
If marking is not present on fuse panel, refer to page 6 of this service bulletin.
IB6
When driving hard on rough roads, the ABS pump may cycle in preparation for the next ABS operation. Also refer to IB3.
IB7
TRACS is a system designed as an aid when starting/driving off if one of the driving wheels has poor traction due to weather conditions or the road surface and is connected to the ABS control module.
TRACS engages automatically at speeds below 40 km/h (25 mph) when one of the drive wheel loses traction. It disengages automatically when speed exceeds 40 km/h (25 mph). The sound which can be heard when the system is operating comes from the ABS system.
TRACS
^ is always active when the ignition is switched on, and may subsequently be activated/deactivated by means of a spring-loaded push-button.
^ A lamp bearing the text "TRACS OFF" is lit when the system is disengaged.
WARRANTY STATEMENT: Claims may be submitted under the New Car Limited Warranty when a manufacturing defect is present using claim type: 01
Operation No. Labor description Time allowance
37912-2 Cable splices in ABS sensor cable replacement 2.0 hr