Speed Signal Circuit: Procedure

1. Check the output waveform.
   Fig 1: Identifying Combination Meter Assembly (Speed Sensor Signal) Connector Terminals & Waveform

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Remove the combination meter assembly with the connector still connected.
   2. Connect an oscilloscope to terminal H14-19 (+S) and body ground.
   3. Turn the engine switch on (IG).
   4. Turn a wheel slowly.
   5. Check the signal waveform according to the condition(s) in the table below.

      Item	Condition
      Tool setting	5 V/DIV., 20 ms./DIV.
      Vehicle condition	Wheel being rotated

      OK

      The waveform is similar to that shown in the illustration.

      HINT: 

      When the system is functioning normally, one wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

      TEXT IN ILLUSTRATION
      
      

      *a	Component with harness connected (Combination Meter Assembly)

NG → See step   4 

OK: Go to next step 

1. Disconnect the H51 windshield wiper relay assembly connector and H14 combination meter assembly connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   H51-24 (SPD) - H14-19 (+S)	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   3