Check For Intermittent Problems

BRAKE CONTROL: VEHICLE STABILITY CONTROL SYSTEM: CHECK FOR INTERMITTENT PROBLEMS

1. CHECK FOR INTERMITTENT PROBLEMS

HINT
A momentary interruption (open circuit) in the connectors and/or wire harness between the sensors and ECUs can be detected using the ECU Data List function of the Techstream.

(a) Turn the ignition switch off and connect a Techstream to the DLC3.

(b) Turn the ignition switch to ON. Follow the directions on the Techstream to display the Data List and select areas where momentary interruption should be monitored.





HINT
* A momentary interruption (open circuit) cannot be detected for 3 seconds after the ignition switch is turned to ON (initial check).
* If the status remains on (ERROR displayed), check the continuity between the ECU and the sensors, or between ECUs.
* The ERROR display on the Techstream remains on for 1 second after the harness signal changes from momentary interruption (open circuit) to normal condition.

ABS/VSC/TRAC:





(c) While observing the screen, gently jiggle the connector or wire harness between the ECU and sensors, or between ECUs.





Result:

ERROR display does not change.

HINT
If the display changes, the connector and/or the wire harness has caused a momentary interruption of the circuit. Repair or replace the connector and/or wire harness as one of them is faulty.

2. SYMPTOM SIMULATION

HINT
The most difficult case in troubleshooting is when no symptoms occur. In such cases, a thorough customer problem analysis must be carried out. Then the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be reproduced. No matter how experienced or skilled a technician may be, if he/she proceeds to troubleshoot without confirming the problem symptoms, he/she will likely overlook something important and make a wrong guess at some points in the repair operation. This leads to a standstill in troubleshooting.

(a) Vibration method: When vibration seems to be the major cause.





HINT
Perform the simulation method only during the primary check period (for approximately 6 seconds after the ignition switch ON).

(1) Slightly vibrate the part of the sensor considered to be the problem cause with your fingers and check whether the malfunction occurs.

(2) Slightly shake the connector vertically and horizontally.

HINT
Shaking the relays too strongly may result in open relays.

(3) Slightly shake the wire harness vertically and horizontally. The connector joint and fulcrum of the vibration are the major areas to be checked thoroughly.