Operating Light Control Rheostat does not Change Light Brightness: Procedure

1. Disconnect the E4 light control rheostat connector.
   Fig 1: Identifying Light Control Rheostat Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   E4-4 (T) - Body ground	Tail light ON	11 to 14 V

3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   E4-5 (E) - Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *a	Front view of wire harness connector (to Light Control Rheostat)

4. Reconnect the light control rheostat connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Remove the light control rheostat but without disconnecting the connector.Refer to REMOVAL .
   Fig 2: Checking Light Control Rheostat (With Waveform Graph)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch to ON.
3. Using an oscilloscope, check the signal waveform of the light control rheostat.

   Item	Contents
   Terminal connection	E4-3 (-) - Body ground
   Tool setting	5 V / DIV, 50 ms / DIV
   Vehicle condition	Ignition switch ON

   OK

   Waveform is as shown in the illustration.

   TEXT IN ILLUSTRATION
   
   

   *a	Component with harness connected (Light Control Rheostat)
   *b	Waveform

   HINT: 

   Duty ratio changes as the illumination dims. (A becomes longer)

4. Reinstall the light control rheostat.

NG → See step   4 

OK: Go to next step 

1. Disconnect the E13 combination meter assembly connector.
2. Disconnect the E4 light control rheostat connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   E13-11 (ILL-) - E4-3 (-)	Always	Below 1 Ω

4. Reconnect the combination meter assembly connector.
5. Reconnect the light control rheostat connector.

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   5