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 Techstream.

1. Turn the engine switch off and connect Techstream to the DLC3.
2. Turn the engine switch on (IG). Follow the directions on 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 engine switch is turned on (IG) (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 Techstream remains on for 1 second after the harness signal changes from momentary interruption (open circuit) to normal condition.
     Fig 1: Harness Signal And Techstream Display Graph

     Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TESTER DISPLAY REFERENCE
   
   

   Tester Display	Measurement Item/Range	Normal Condition
   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
   Master cylinder Open	Master cylinder pressure 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.

   Result: 

   ERROR display does not change. 

   HINT:

   The connector and/or wire harness will be in momentary interruption (open circuit) if the display changes. Repair or replace the connector and/or wire harness as one of them is faulty.