Diesel Data: Automotive Repair

Operating Light Control Rheostat Does Not Change Light Brightness








METER: METER / GAUGE SYSTEM (for Sedan): Operating Light Control Rheostat does not Change Light Brightness

Operating Light Control Rheostat does not Change Light Brightness

DESCRIPTION

The combination meter assembly controls the combination meter illumination in accordance with the light control signals from the light control rheostat.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM (RHEOSTAT)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Select the item below in the Data List, and read the value displayed on the Techstream.
Body Electrical / Combination Meter / Data List::






OK:
Light brightness can be changed within the specified range by actual operation.
NG -- INSPECT FUSE (GAUGE)
OK -- REPLACE COMBINATION METER ASSEMBLY
2. INSPECT FUSE (GAUGE)
(a) Remove the GAUGE fuse from the main body ECU.
(b) Measure the resistance.
OK:
Below 1 Ohms
(c) Reinstall the GAUGE fuse.
NG -- REPLACE FUSE
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (FUSE (GAUGE) - LIGHT CONTROL RHEOSTAT)




(a) Disconnect the D29 light control rheostat connector.
(b) Measure the voltage.
Standard voltage:





(c) Reconnect the light control rheostat connector.
OK -- INSPECT LIGHT CONTROL RHEOSTAT
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - LIGHT CONTROL RHEOSTAT)




(a) Disconnect the D29 light control rheostat connector.
(b) Disconnect the 4P main body ECU connector.
(c) Measure the resistance.
Standard resistance:





(d) Reconnect the light control rheostat connector.
(e) Reconnect the main body ECU connector.
NG -- REPLACE MAIN BODY ECU
OK -- Continue to next step.
5. INSPECT LIGHT CONTROL RHEOSTAT




(a) Remove the light control rheostat but without disconnecting the connector.
(b) Turn the ignition switch ON.
(c) Using an oscilloscope, check the signal waveform of the light control rheostat.






OK:
Waveform is as shown in the illustration.
HINT: Duty ratio changes as the illumination dims. (A becomes longer)
(d) Reinstall the light control rheostat.
NG -- REPLACE LIGHT CONTROL RHEOSTAT
OK -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - LIGHT CONTROL RHEOSTAT)




(a) Disconnect the D1 combination meter assembly connector.
(b) Disconnect the D29 light control rheostat connector.
(c) Measure the resistance.
Standard resistance:





(d) Reconnect the combination meter assembly.
(e) Reconnect the light control rheostat connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE COMBINATION METER ASSEMBLY