The windshield wiper relay assembly receives a vehicle speed signal from the combination meter assembly 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 following diagram will not operate normally.
INSPECT COMBINATION METER ASSEMBLY (SPEED SENSOR SIGNAL)
Component with harness connected
(Combination Meter Assembly)
Check the output waveform.
Remove the combination meter assembly with the connector still connected.
Connect an oscilloscope to terminal H14-19 (+S) and body ground.
Turn the engine switch on (IG).
Turn a wheel slowly.
Check the signal waveform according to the condition(s) in the table below.
|Tool setting||5 V/DIV., 20 ms./DIV.|
|Vehicle condition||Wheel being rotated|
|The waveform is similar to that shown in the illustration.|
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.
GO TO METER / GAUGE SYSTEM Click here
CHECK HARNESS AND CONNECTOR (WINDSHIELD WIPER RELAY ASSEMBLY - COMBINATION METER ASSEMBLY)
Disconnect the H51 windshield wiper relay assembly connector and H14 combination meter assembly connector.
Measure the resistance according to the value(s) in the table below.
REPAIR OR REPLACE HARNESS OR CONNECTOR