Speed Signal Circuit: Procedure

1. Check the input waveform.
   Fig 1: Identifying L27 Combination Meter Connector Terminal And Output Waveform

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Remove the combination meter assembly with the connector(s) still connected.
   2. Connect an oscilloscope to terminal L27-7 (+S) and body ground.
   3. Turn the power switch on (IG).
   4. Turn the 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

      TEXT IN ILLUSTRATION
      
      

      *a	Component with harness connected (Combination Meter Assembly)

      OK

      The waveform is displayed as 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.

NG → See step   4 

OK: Go to next step 

1. Disconnect the L140 vehicle approaching speaker controller connector.
2. Disconnect the L27 combination meter assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L140-6 (SPD) - L27-7 (+S)	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   3