Speed Signal Circuit

LIGHTING (EXT): LIGHTING SYSTEM: Speed Signal Circuit
- Speed Signal Circuit

DESCRIPTION

The headlight leveling ECU assembly receives the vehicle speed signal from the combination meter sub-assembly.

HINT
* 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.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK METER / GAUGE SYSTEM

(a) The circuits that send vehicle speed signals to this system are inspected in the meter section Speed Signal Circuit.

(b) 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.

NEXT -- Continue to next step.

2. CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU ASSEMBLY - COMBINATION METER SUB-ASSEMBLY)

(a) Disconnect the L27 combination meter sub-assembly connector.

(b) Disconnect the A48 headlight leveling ECU assembly connector.

(c) 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 SUB-ASSEMBLY (OUTPUT WAVEFORM)

(a) Check the output waveform.





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

(2) Connect an oscilloscope to terminal L27-15 (+S) and body ground.

(3) Turn the power switch on (IG).

(4) Check the signal waveform according to the condition(s) in the table below.





OK:

The waveform is displayed as shown in the illustration.

Text in 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.

NG -- REPLACE METER CIRCUIT PLATE Removal

OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Exterior Lighting System