The navigation ECU receives a vehicle speed signal from the combination meter assembly.
A voltage of 12 V or 5 V is output from each ECU 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 its respective systems based on this 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.
|*1||to Other Systems|
|*2||Combination Meter Assembly|
CHECK COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)
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 O3-19 (+S) and body ground.
Turn the power switch on (IG).
Turn a wheel slowly.
Check the signal waveform according to the condition(s) in the table below.
|Measurement terminal||O3-19 (+S) - Body ground|
|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 (NAVIGATION ECU - COMBINATION METER ASSEMBLY)
Disconnect the O150 navigation ECU connector.
Disconnect the O3 combination meter assembly connector.
Measure the resistance according to the value(s) in the table below.
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here
REPAIR OR REPLACE HARNESS OR CONNECTOR