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 by using the ECU Data List function of Techstream.

1. Turn the ignition switch OFF and connect Techstream to the DLC3.
2. Turn the ignition switch ON.
3. Follow the prompts on Techstream to display the Data List and select areas where a momentary interruption should be monitored.

   HINT:

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

     Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   ABS/VSC/TRAC: 

   MEASUREMENT ITEM/RANGE AND DIAGNOSTIC NOTE
   
   

   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	Deceleration 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	-
   Master Cylinder Open	Master cylinder pressure sensor open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-

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

   OK: ERROR display does not change. 

   HINT:

   The connector and/or wire harness have a momentary interruption (open circuit) if the display changes. Repair or replace the connector and wire harness if either of them is faulty.