Diagnostic Strategies - Antilock Brakes / Traction Control Systems
FOREWORD [ABS/TCS]^ Before performing the steps in Symptom Troubleshooting, perform the On-board Diagnostic Inspection. To check the DTC, follow the DTC Inspection steps.
PRECAUTION [ABS/TCS]
1. Any one or a combination of the ABS warning light, BRAKE system warning light, TCS indicator light, and TCS OFF light illuminate even when the system is normal.
2. Precautions during servicing of ABS/TCS. The ABS/TCS is composed of electrical and mechanical parts. It is necessary to categorize malfunctions as being either electrical or hydraulic when performing troubleshooting.
1) Malfunctions in electrical system
^ The ABS/TCS HU/CM has an on-board diagnostic function. With this function, any one or a combination of the ABS warning light, BRAKE system warning light, TCS indicator light, and TCS OFF light will come on when there is a problem in the electrical system. Also, past and present malfunctions are recorded in the ABS/TCS HU/CM. This function can find malfunctions that do not occur during periodic inspections. Connect the WDS or equivalent to the DLC-2. Stored malfunctions will be displayed in the order of occurrence. To find out the causes of ABS/TCS malfunctions, use these on-board diagnostic results.
^ If a malfunction occurred in the past but is now normal, the cause is likely a temporary poor connection of the harness. The ABS/TCS HU/CM usually operates normally. Be careful when searching for the cause of malfunction.
^ After repair, it is necessary to clear the DTC from the ABS/TCS HU/CM memory. Also, if the ABS/TCS related parts have been replaced, verify that the no DTC has been displayed after repairs.
^ After repairing the ABS wheel-speed sensor or ABS sensor rotor, or after replacing the ABS/TCS HU/CM, the ABS warning light may not go off (*) even when the ignition switch is turned ON. In this case, drive the vehicle at a speed of more than 10 km/h (6.2 mph), make sure that ABS warning light goes off, and then clear the DTC.
^ The BRAKE system warning light also illuminates when there is any rear wheel deformations.
^ When repairing, if the ABS/TCS related connectors are disconnected and the ignition switch is turned ON, the ABS/TCS HU/CM will mistakenly detect a fault and record it as a malfunction.
^ To protect the ABS/TCS HU/CM, make sure the ignition is off before connecting or disconnecting the ABS/TCS HU/CM connector.
2) Malfunctions in hydraulic system
^ Symptoms in a hydraulic system malfunction are similar to those in a conventional brake malfunction. However, it is necessary to determine if the malfunction is in an ABS component or the conventional brake system.
^ The ABS hydraulic unit contains delicate mechanical parts. If foreign materials get into the component, the ABS may fail to operate. Also, it will likely become extremely difficult to find the location of the malfunction in the event that the brakes operate but the ABS does not. Make sure foreign materials do not get inside when servicing the ABS (e.g. brake fluid replacement, pipe removal).
Intermittent Concern Troubleshooting
Vibration method
If malfunction occurs or becomes worse while driving on a rough road or when the engine is vibrating, perform the steps below.
Note:
^ There are several reasons why vehicle or engine vibration could cause an electrical malfunction. Some of the things to check for are:
- Connectors not fully seated.
- Wire harnesses not having full play
- Wires laying across brackets or moving parts.
- Wires routed too close to hot parts.
^ An improperly routed, improperly clamped, or loose harness can cause wiring to become pinched between parts.
^ The connector joints, points of vibration, and places where wire harnesses pass through the firewall, body panels, etc. are the major areas to be checked.
Inspection method for switch connectors or wires
1. Connect WDS or equivalent to DLC-2.
2. Turn ignition key to ON (engine off).
Note:
^ If engine starts and runs, perform the following steps at idle.
3. Access PIDs for the switch you are inspecting.
4. Turn switch on manually.
5. Shake each connector or wire harness a bit vertically and horizontally while monitoring the PID. If PID value is unstable, check for poor connection.
Inspection method for sensor connectors or wires
1. Connect WDS or equivalent to DLC-2.
2. Turn ignition key to ON (engine off).
Note:
^ If engine starts and runs, perform the following steps at idle.
3. Access PIDs for the switch you are inspecting.
4. Shake each connector or wire harness a bit vertically and horizontally while monitoring the PID. It PID value is unstable, check for poor connection.
Inspection method for sensors
1. Connect WDS or equivalent to DLC-2.
2. Turn ignition key to ON (engine off).
Note:
^ If engine starts and runs, perform the following steps at idle.
3. Access PIDs for the switch you are inspecting.
4. Vibrate the sensor slightly with your finger.
^ If PID value is unstable or malfunction occurs, check for poor connection and/or poorly mounted sensor.
Malfunction data monitor method
1. Perform malfunction reappearance test according to malfunction reappearance mode and malfunction data monitor. The malfunction cause is found in the malfunction data.
Connector terminal check method
1. Check the connection condition of each female terminal.
2. Insert male terminal; fit the female terminal side to female terminal and check to see whether the malfunction is in the female terminal or not.