Description of On-Board Diagnostics
General InformationABS malfunction can be classified into two types, those which can be detected by the ABS warning light and those which can be detected as a vehicle abnormality by the driver. In either case, locate the fault in accordance with the "BASIC DIAGNOSTIC FLOWCHART" and repair. Please refer to Brakes / Testing and Inspection for the diagnosis of mechanical troubles such as brake noise, brake judder (brake pedal or vehicle vibration felt when braking), uneven braking, and parking brake trouble.
ABS Service Precautions
Required Tools and Items:
^ Box Wrench
^ Brake Fluid
^ Special Tool
Some diagnosis procedures require the installation of a special tool.
J-39200 High Impedance Multimeter
When circuit measurements are requested, use a circuit tester with high impedance.
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.
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 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 30 km/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".
NOTICE:
^ 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.
NOTICE: 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.
Normal Operation
"ABS" Warning Light
When the ignition is first moved from "OFF" to "ON" , the amber "ABS" warning light will turn "ON" . The "ABS" warning light will turn "ON" during engine starting and will usually stay "ON" for approximately three seconds after the ignition switch is returned to the "ON" position. The warning light should remain "OFF" at all other times.