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 Techstream.

1. Turn the ignition switch off.
2. Connect Techstream to the DLC3.
3. Turn the ignition switch on (IG).
4. Turn Techstream on.
5. Follow the directions on Techstream to display the Data List and select areas where momentary interruptions should be monitored.
   Fig 1: Display Harness Signals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT: 

   • A momentary interruption (open circuit) cannot be detected for 3 seconds after the ignition 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 Techstream will remain displayed 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	-
   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	-
   IG Voltage Value Increased	IG voltage value increase detection / ERROR or NORMAL	ERROR: Increase NORMAL: Normal	-
   FR Speed Sensor Voltage Open	FR speed sensor voltage open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   FL Speed Sensor Voltage Open	FL speed sensor voltage open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   RR Speed Sensor Voltage Open	RR speed sensor voltage open detection / ERROR or NORMAL	ERROR: Momentary interruption NORMAL: Normal	-
   RL Speed Sensor Voltage Open	RL speed sensor 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	-
   Brake Pedal Switch Open	Brake pedal load sensing switch open detection / ERROR or NORMAL	ERROR: Momentary interruption 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.
   Fig 2: Jiggling Connector Or Wire Harness Between ECU And Sensors

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   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.