Introduction
How to Perform Trouble Diagnoses for Quick and Accurate RepairINTRODUCTION
The ABS/TCS/VDC/HDC/HSA system has an electronic control unit to control major functions. The control unit accepts input signals from sensors and controls actuator operation. It is also important to check for air leaks in the booster or lines, lack of brake fluid, or other malfunctions in the brake system.
It is much more difficult to diagnose a malfunction that occurs intermittently rather than continuously. Most intermittent conditions are caused by poor electrical connections or damaged wiring. In this case, careful checking of suspicious circuits may help prevent the replacement of good parts.
A visual check only may not find the cause of the malfunction, so a road test should be performed.
Before undertaking actual checks, take just a few minutes to talk with a customer who approaches with an ABS/TCS/VDC/HDC/HSA complaint. The customer is a very good source of information, especially for intermittent conditions. Through the talks with the customer, find out what symptoms are present and under what conditions they occur.
Start your diagnosis by looking for "conventional" malfunctions first. This is one of the best ways to troubleshoot brake malfunctions on an ABS/TCS/VDC/HDC/HSA equipped vehicle. Also check related Service Bulletins for information.
For Fast and Accurate Diagnosis
PRECAUTIONS FOR DIAGNOSIS
^ Before performing diagnosis, always read precautions. Refer to BRC-86, "PRECAUTIONS".
^ If ABS actuator and electric unit (control unit), steering angle sensor, steering system parts or suspension system parts have been replaced, or if alignment has been adjusted, be sure to adjust neutral position of steering angle sensor before driving.
^ After diagnosis is finished, be sure to erase memory.
^ When checking continuity and voltage between units, be sure to check for disconnection, looseness, bend, or collapse of connector terminals. If any non-standard condition is found, repair or replace connector terminals.
^ For intermittent symptoms, possible cause is malfunction in harness, harness connector, or terminals. Move harness, harness connector, and terminals to check for poor connections.
^ If a circuit tester is used for the check, be careful not to forcibly extend any connector terminal.
^ To use CONSULT-II to perform self-diagnosis of ABS actuator and electric unit (control unit), active tests, or work support, first stop work, then connect CONSULT-II and select "ABS". Self-Diagnosis
^ CONSULT-II self-diagnosis results are displayed without regard to occurrence timing. In some cases later ones (timing value is small) appear on the next screen.
^ When self-diagnostic results of CONSULT-II show a malfunction, if CONSULT-II active test is performed, an engine system error may be indicated. In this case, start engine to resume the normal screen.
^ VDC/TCS/ABS system electronically controls brake operation and engine output. The following symptoms may be caused by normal operations:
