TROUBLE SHOOTING & DIAGNOSIS 14. General information: While the ignition is in position II, the ABS ECU monitors the system for faults. Diagnostic information and system function monitoring can be accessed by connecting diagnostic software to the vehicle diagnostic connector. After detecting a fault, the ABS ECU will select a suitable default strategy, which will retain, if possible, some operational ABS capability. If ABS is not active, conventional braking will be remaining available. Fault codes are stored in the ECU’s memory, which can be accessed, read and then cleared when the fault is rectified. (a) During driving the vehicle with ABS operative: 1.Observe warning lights, check parking brake/fluid warning light extinguishes after initial bulb check or when parking brake is released, indicating that power assistance is available. 2. In road conditions where surface friction is sufficient to slow or stop the vehicle without wheel lock, ABS does not operate. 3. In an emergency braking situation, if one or more wheels begin to slow rapidly in relation to vehicle speed, ABS will detect wheel-locking tendency and will regulate brake pressure to maintain wheel rotation. (b) Brake application with partial failure: 1. When power assistance is not available, ABS braking is not operative. Both warning lights are illuminated. Braking effort is available from master cylinder only. This result in longer pedal travel and greater pedal effort required to decelerate vehicle. 2. If master cylinder fails, i.e. there is insufficient fluid in master cylinder to create pressure, braking to all four wheels is retained and ABS remains operative. The red warning light (fluid level indica-tor lamp) will be illuminated if cause of the master cylinder failure is a fluid leak and level in fluid reservoir is low enough to actuate fluid level switch. WARNING If a fault develops in the brake system, it is essential that it be investigated immediately. NOTE If, during braking, a drastically reduced • resistance is detected at pedal and braking effectiveness is very much reduced, failure of the non-powered (master cylinder) portion of system is indicated. When this occurs, DO NOT PUMP BRAKE PEDAL. Push the pedal through free movement to obtain braking effort from the power circuit. It is essential that items such as extra floor mats not obstruct brake pedal travel. NOTE Foot pressure on the pedal, using master • cylinder only, will not achieve the same degree of braking as is available from power assistance. WARNING Longer pedal travel is required, but power assisted braking is available at reduced efficiency. NOTE The hydraulic connections to the hydraulic • modulator can be crossed over; the ECU self-diagnosis will not detect it as a fault; nor will it cause the system to be shut down or cause a fault code to be logged in the ECU. When the hydraulic modulator is exchanged or repaired, the brake pipes to the solenoids must be tested for correct assignment using a diagnostics tester. When the inlet and outlet valve are activated, e.g. on the front left wheel, this must generate the necessary changes at the wheel. If this does not happen, the pipes have been crossed over. This will cause the system to function incorrectly. BRAKE_PETROL 60
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