Speed Signal Circuit

WIPER / WASHER: WIPER AND WASHER SYSTEM (w/ Rain Sensor): Speed Signal Circuit
- Speed Signal Circuit

DESCRIPTION

The windshield wiper relay assembly receives a vehicle speed signal from the combination meter to control the automatic windshield wiper system.

A voltage of 12 V or 5 V is output from the combination meter assembly and then input to the skid control ECU.

A voltage of 12 V or 5 V is output from each ECU or relay and then input to the combination meter assembly.

The signal is changed to a pulse signal at the transistor in the combination meter assembly.

Each ECU controls the respective system based on the pulse signal.

If a short occurs in any of the ECUs or in the wire harness connected to an ECU, all systems in the diagram below will not operate normally.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK COMBINATION METER SYSTEM

(a) The circuit that sends vehicle speed signals to the combination meter system is inspected in the meter section Component Tests and General Diagnostics.

NEXT -- Continue to next step.

2. CHECK HARNESS AND CONNECTOR (WINDSHIELD WIPER RELAY ASSEMBLY - COMBINATION METER)

(a) Disconnect the D78 windshield wiper relay assembly connector and D18 combination meter connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. INSPECT COMBINATION METER (SPEED SENSOR SIGNAL)

(a) Check the output waveform.





(1) Remove the combination meter assembly with the connector still connected 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.





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





NG -- REPLACE COMBINATION METER Removal

OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Wiper and Washer System (w/ Rain Sensor)