Check For Intermittent Problems

HINT

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

1. Turn the engine switch off.
2. Connect the Techstream to the DLC3.
3. Turn the engine switch on (IG).
4. Turn the Techstream on.
5. Follow the directions on the Techstream to display the Data List and select areas where momentary interruptions 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 ERROR display remains displayed, check for continuity between the ECUs and the sensors, or between ECUs
   • The ERROR display on the Techstream will remain displayed for 1 second after the harness signal changes from momentary interruption (open circuit) to normal condition
     Fig 1: Momentary Interruption Graph

     Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

     ABS/VSC/TRAC 

     ABS/VSC/TRAC NORMAL CONDITION
     
     

     Tester Display	Measurement Item / Range	Normal Condition	Diagnostic Note
     FR Speed Open	Front speed sensor RH open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     FL Speed Open	Front speed sensor LH open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     RR Speed Open	Rear speed sensor RH open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     RL Speed Open	Rear speed sensor LH 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	-
     IG Voltage Value Decreased	IG voltage value decrease detection / ERROR or NORMAL	ERROR Decrease NORMAL Normal	-
     FR Speed Sensor Voltage Open	Front speed sensor RH voltage open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     FL Speed Sensor Voltage Open	Front speed sensor LH voltage open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     RR Speed Sensor Voltage Open	Rear speed sensor RH voltage open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     RL Speed Sensor Voltage Open	Rear speed sensor LH voltage open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     M/C Pressure Sensor Noise	Master cylinder pressure sensor noise detection / ERROR or NORMAL	ERROR Malfunction NORMAL Normal	-
     Yaw Rate Sensor Voltage Open	Yaw rate sensor voltage open detection / ERROR or NORMAL	ERROR Momentary interruption NORMAL Normal	-
     EFI Communication Invalid	EFI communication invalid detection / ERROR or NORMAL	ERROR Invalid NORMAL Normal	-

6. While observing the screen, gently jiggle the connectors or wire harnesses between the ECUs and sensors, or between ECUs

   OK: NORMAL display appears. 

   HINT

   The connector and/or wire harness has a momentary interruption (open circuit) if the display changes Repair or replace the connectors and/or wire harnesses as one of them is faulty