Speed Signal Circuit: Procedure

1. The circuit that sends vehicle speed signals to the combination meter system is inspected in the meter information. Refer to Speed Signal Circuit .

NEXT: Go to next step 

1. Disconnect the D78 windshield wiper relay assembly connector and D18 combination meter connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   D78-19 (SPD) - D18-10 (+S)	Always	Below 1 Ω
   D78-19 (SPD) or D18-10 (+S) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Check the output waveform.
   Fig 1: Inspecting Combination Meter (Speed Sensor Signal) With Waveform

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Remove the combination meter assembly with the connector still connected. Refer to REMOVAL .
   2. Connect an oscilloscope to terminal D18-10 (+S) and body ground.
   3. Turn the ignition switch to ON.
   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	Driving at approx. 20 km/h (12 mph)

      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.

   TEXT IN ILLUSTRATION
   
   

   *a	Component with harness connected (Combination Meter Assembly)

NG → See step   5 

OK → See step   4