Initial Inspection and Diagnostic Overview
Anti-Lock Control - Stability AssistPrinciple of operation
The anti-lock brake system (ABS) modulates brake pressure on each wheel independently to maintain vehicle stability during braking. The ABS continually monitors the rotational velocity of each wheel anytime the ignition switch is in the ON position and determines if a tire is skidding when the brakes are applied. Only then does the ABS intervene to modulate the brake pressure to the skidding wheel. The modulation continues until the wheel rotates freely. The brake pressure is then restored and the modulate/restore cycle is repeated whenever skidding is detected. This cycle occurs at a rate of several times per second.
The ABS module is capable of detecting the following system conditions:
- hydraulic valve failure
- wheel speed sensor failure
- ABS power relay short circuit
- interconnect failures to the ABS sensors, power and ground to the ABS module
- over/under voltage conditions
The ABS provides failure messages, via the ABS indicator, in the instrument cluster. Failure of the ABS module, for whatever reason, will not compromise the normal operation of the brake system.
Dynamic Stability Control (DSC) equipped vehicles
DSC maximizes vehicle stability under all conditions. The DSC system compares actual vehicle course to that intended by the driver. If the intended course differs from the actual course due to over steer or under steer conditions, the DSC system will brake individual wheels and reduce engine torque to bring the vehicle back to the driver's intended direction. By using a combined yaw rate sensor and lateral accelerometer, the vehicles rotational motion around its vertical axis and centrifugal forces generated while cornering are calculated to determine the vehicle's actual behavior. Using additional sensors for detecting steering wheel position and road wheel speed enables the system to recognize the driver's intentions.
DSC/TCS is enabled/disabled via the DSC/TCS ON/OFF switch. When the switch is in the OFF position, the amber DSC/TCS warning lamp solidly illuminates within the instrument cluster message center. The DSC/TCS is automatically activated when the ignition is switched on. The DSC/TCS also provides failure messages via the instrument cluster message center.
On 2.0L vehicles the traction control system (TCS) is incorporated into the anti-lock brake system (ABS). Where DSC is fitted, traction control is a function within the DSC system. The vehicle's driven wheels are continually monitored for wheel spin relative to the calculated reference speed and to each other. If wheel spin is detected, the traction control function intervenes independently of the driver, applying brake pressure to the slipping wheel and reducing the engine drive torque supply. Meanwhile, brake pressure is modulated by the traction control until traction is reestablished. Traction control brake actuation is diminished above 40 km/h (25 mph). Above this speed traction control relies primarily on engine torque reduction.
The traction control brake intervention is automatically disabled whenever the brakes exceed a temperature limit. The traction brake intervention will remain disabled until the brakes have cooled, irrespective of ignition switch position or ignition switch cycling.
Inspection and Verification
1. Verify the customer concern.
2. Confirm if the ABS warning light was illuminated, or still is.
NOTE: An intermittent fault may allow the warning light to go off. This does not necessarily mean the fault is not present. Some warnings will appear to clear when the ignition is cycled. This is often because the warning has flagged as a result of one of the vehicle's on-board diagnostic routines having run to detect the fault. If the same routine is not run when the ignition is switched ON, the warning will not reflag until the routine does run.
3. In order to confirm the customer concern, it may be necessary to follow a drive cycle which will enable the system to perform it's diagnostic routine (see below).
Diagnostic Drive Cycles:
Visual Inspection
1. Visually inspect for obvious signs of mechanical or electrical damage.
Fuse Identification Table
Fuse Identification Table:
1. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
2. If the cause is not visually evident and the Jaguar approved diagnostic system is not available, use a fault code reader to retrieve the fault codes before proceeding to the Diagnostic Trouble Code (DTC) Index Chart.