5A4-8 ANTI-LOCK BRAKE SYSTEM (ABS) General Service Precautions The following are general precautions which should be observed when servicing and diagnosing the Anti-lock Brake System and/or other vehicle systems. Failure to observe these precautions may result in Anti-lock Brake System damage. If welding work is to be performed on the vehicle using an electric arc welder, the EHCU connector should be disconnected before the welding operation begins. The EHCU connector should never be connected or disconnected with the ignition “ON”. The EHCU is not separately serviceable and must be replaced as assemblies.
Do not disassemble any component which is designated as non- serviceable in this Section. If only rear wheels are rotated using jacks or drum tester, the system will diagnose a speed sensor malfunction and the “ABS” warning light will illuminate. But actually no trouble exists. After inspection stop the engine once and re-start it, then make sure that the “ABS” warning light does not illuminate. If the battery has been discharged The engine may stall if the battery has been completely discharged and the engine is started via jumper cables. This is because the Anti-lock Brake System (ABS) requires a large quantity of electricity.
In this case, wait until the battery is recharged, or set the ABS to a non-operative state by removing the fuse for the ABS. After the battery has been recharged, stop the engine and install the ABS fuse. Start the engine again, and confirm that the ABS warning light does not light. case of such trouble as can be detected by the driver as a vehicle symptom, however, it is necessary to give a test drive following the test procedure mentioned below, thereby reproducing the symptom for trouble diagnosis on a symptom basis: 1. Start the engine and make sure that the “ABS” W/L goes OFF. If the W/L remains ON, it means that the Diagnostic Trouble Code (DTC) is stored.
Therefore, read the code and locate the fault. 2. Start the vehicle and accelerate to about 30km/h (19 mph) or more. 3. Slowly brake and stop the vehicle completely. 4. Then restart the vehicle and accelerate to about 40 km/h (25 mph) or more. 5. Brake at a time so as to actuate the ABS and stop the vehicle. 6. Be cautious of abnormality during the test. If the W/L is actuated while driving, read the DTC and locate the fault. 7. If the abnormality is not reproduced by the test, make best efforts to reproduce the situation reported by the customer. 8. If the abnormality has been detected, repair in accordance with the “SYMPTOM DIAGNOSIS”. NOTE:
Be sure to give a test drive on a wide, even road with little traffic. If an abnormality is detected, be sure to suspend the test and start trouble diagnosis at once. “ABS” Warning Light When ABS trouble occurs and actuates when possible the “ABS” warning light, the trouble code corresponding to the trouble is stored in the EHCU. Only the ordinary brake system is available when the ABS is turned OFF. When the “ABS” warning light is actuated, if the starter switch is set ON after setting it OFF once, the EHCU checks up on the entire system and, if there is no abnormality, judges ABS to work currently and the warning light works normally even though the trouble code is stored. NOTE:
Illumination of the “ABS” warning light indicates that anti-lock braking is no longer available. Power assisted braking without anti-lock control is still available. Note on Intermittents As with virtually any electronic system, it is difficult to identify an intermittent failure. In such a case duplicating the system malfunction during a test drive or a good description of vehicle behavior from the customer may be helpful in locating a “most likely” failed component or circuit. The symptom diagnosis chart may also be useful in isolating the failure. Most intermittent problems are caused by faulty electrical connections or wiring.
When an intermittent failure is encountered, check suspect circuits for: Suspected harness damage. Poor mating of connector halves or terminals not fully seated in the connector body (backed out). Improperly formed or damaged terminals. Normal Operation “ABS” Warning Light When the ignition is first moved from “OFF” to “ON”, the amber “ABS” warning light will turn “ON” for 2 seconds and will turn “OFF”. Test Driving ABS Complaint Vehicles In case that there has been an malfunction in the lighting pattern of “ABS” warning light, the fault can be located in accordance with the “DIAGNOSIS BY “ABS” WARNING LIGHT ILLUMINATION PATTERN”. In