Anti-Lock/Traction Control: Description

NOTE: Discovery and Discovery II can be identified by VIN number. The 4th and 5th digits of the VIN are JY on Discovery, TY on Discovery II. This article applies to Discovery II. For information on Discovery, see ANTI-LOCK - DISCOVERY article.

NOTE: Some vehicles have optional Self Leveling System (SLS). SLS CPU shares its housing with the ABS CPU, but operates independently. On all vehicles, with or without SLS, manufacturer refers to Anti-Lock Brake System (ABS) Electronic Control Module (ECU) as Self Leveling and Anti-Lock Brake System (SLABS) ECU. SLS is not part of ABS system and is not covered in this article.

Brake system is diagonally split, dual hydraulic system with vacuum servo power assistance. ABS system is 4-channel, all terrain system. Braking at each wheel is individually controlled. ABS system can detect and will adjust braking for smooth road and rough road conditions. The SLABS ECU monitors each wheel 250 times per seconds and can cycle brakes up to 10 times per second. The ABS system consists of SLABS ECU, wheel speed sensors, modulator, brake master cylinder, brake servo assembly (vacuum booster), switches, relays, fuses and wiring harness. See Fig 1 and Fig 2 .

Standard features on all models are Anti-Lock Brake System (ABS), Electronic Brake Distribution (EBD), Electronic Traction Control (ETC) and Hill Descent Control (HDC). The ABS system is designed to prevent wheel lock-up during hard braking. This allows driver to maintain vehicle steering control and stability. EBD uses braking intervention to control distribution of hydraulic pressure between front and rear axles to maintain vehicle stability during braking. EBD replaces mechanical pressure limiting valve of previous system. ETC uses brake intervention to prevent wheel spin and maintain even torque distribution to wheels. ETC improves traction on loose and slippery surfaces. HDC uses brake intervention to provide controlled descent ability in off road conditions when engine braking is insufficient to control vehicle speed.

NOTE: For more information on brake system, see DISC article.

Fig 1: Identifying Anti-Lock Brake System Control Components

Courtesy of LAND ROVER NORTH AMERICA, INC.

Fig 2: Locating ABS System Hydraulic Components

Courtesy of LAND ROVER NORTH AMERICA, INC.