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.

1. Turn the ignition switch off and connect a Techstream to the DLC3.
2. 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.
   Fig 1: ECU Blinking Pattern

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   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:
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   FR Speed Open	FR speed sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   FL Speed Open	FL speed sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   RR Speed Open	RR speed sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   RL Speed Open	RL speed sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   EFI Communication Open	EFI communication open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   Yaw Rate Open	Yaw rate sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   Deceleration Open	Acceleration sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   Steering Open	Steering angle sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-

3. While observing the screen, gently jiggle the connector or wire harness between the ECU and sensors, or between ECUs.
   Fig 2: Shaking Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   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.

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.

1. Vibration method: When vibration seems to be the major cause.
   Fig 3: Identifying Simulation Method

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   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.