The headlight leveling ECU assembly receives the vehicle speed signal from the combination meter sub-assembly.
A voltage of 12 V or 5 V is output from each ECU and then input to the combination meter. The signal is changed to a pulse signal at the transistor in the combination meter. 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.
CHECK METER / GAUGE SYSTEM
The circuits that send vehicle speed signals to this system are inspected in the meter section Click here.
During inspection for the meter/gauge system, if there is an instruction that indicates to go back to inspections for the lighting system, proceed to the next step.
CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU ASSEMBLY - COMBINATION METER SUB-ASSEMBLY)
Disconnect the L27 combination meter sub-assembly connector.
Disconnect the A48 headlight leveling ECU assembly connector.
Measure the resistance according to the value(s) in the table below.
REPAIR OR REPLACE HARNESS OR CONNECTOR
INSPECT COMBINATION METER SUB-ASSEMBLY (OUTPUT WAVEFORM)
Component with harness connected
(Combination Meter Sub-assembly)
Check the output waveform.
Remove the combination meter sub-assembly with the connector still connected.
Connect an oscilloscope to terminal L27-15 (+S) and body ground.
Turn the power switch on (IG).
Check the signal waveform according to the condition(s) in the table below.
|Tool setting||5 V/DIV., 20 ms./DIV.|
|Vehicle condition||Driving at approximately 20 km/h (12 mph)|
|The waveform is displayed as 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.
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here
REPLACE METER CIRCUIT PLATE Click here
REPLACE COMBINATION METER SUB-ASSEMBLY Click here