Illumination Circuit [11/2015 - 08/2019]: Procedure

2018 Toyota Prius Two EcoSECTION Procedure
  1. CHECK ILLUMINATION 
    1. Check if the illumination for the radio and display receiver assembly, steering pad switch assembly, heater control switch or others (hazard switch, transmission control switch, etc.) comes on when the light control switch is turned to the head or tail position.

      Result

      Result Proceed to
      Illumination comes on for all components except steering pad switch assembly. A
      Illumination comes on for all components except radio and display receiver assembly. B
      Illumination comes on only for steering pad switch assembly. C
      No illumination comes on (radio and display receiver assembly, hazard switch, heater control switch, etc.). D

    Result: 

    See step  5

    Result: 

    GO TO METER / GAUGE SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2015 - ] 

    Result: 

    GO TO LIGHTING SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2015 - ] 

    Result: 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (ILLUMINATION SIGNAL) 
    1. Disconnect the F21 spiral cable with sensor sub-assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      F21-13 (IL+2) - Body ground Power switch off
      Light control switch in tail or head position
      11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. INSPECT STEERING PAD SWITCH ASSEMBLY 
    1. Remove the steering pad switch assembly.

      Refer to REMOVAL [11/2015 - 12/2018] , or refer to REMOVAL [12/2018 - 07/2020]

    2. Inspect the steering pad switch assembly.

      Refer to REMOVAL [11/2015 - 12/2018] , or refer to REMOVAL [12/2018 - 07/2020]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE STEERING PAD SWITCH ASSEMBLY. Refer to  REMOVAL [11/2015 - 12/2018]  , or refer to  REMOVAL [12/2018 - 07/2020] 

    Result: 

    OK 

    See step  4

  4. INSPECT SPIRAL CABLE WITH SENSOR SUB-ASSEMBLY 
    1. Remove the spiral cable with sensor sub-assembly.

      Refer to REMOVAL [11/2015 - 12/2018] , or refer to REMOVAL [12/2018 - 07/2020]

    2. Inspect the spiral cable with sensor sub-assembly.

      Refer to INSPECTION [11/2015 - 12/2018] , or refer to INSPECTION [12/2018 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SPIRAL CABLE WITH SENSOR SUB-ASSEMBLY - RADIO AND DISPLAY RECEIVER ASSEMBLY, METER CIRCUIT PLATE) 

    Result: 

    NG 

    REPLACE SPIRAL CABLE WITH SENSOR SUB-ASSEMBLY. Refer to  REMOVAL [11/2015 - 12/2018]  , or refer to  REMOVAL [12/2018 - 07/2020] 

  5. CHECK HARNESS AND CONNECTOR (ILLUMINATION SIGNAL) 
    1. Disconnect the F32 radio and display receiver assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      F32-10 (ILL+) - Body ground Power switch off
      Light control switch in tail or head position
      11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (RADIO AND DISPLAY RECEIVER ASSEMBLY - METER CIRCUIT PLATE) 
    1. Disconnect the F33 radio and display receiver assembly connector.
    2. Disconnect the F6 meter circuit plate connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      F33-5 (ILL-) - F6-39 (ILL-) Always Below 1 Ω
      F33-5 (ILL-) or F6-39 (ILL-) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [11/2015 - 08/2019] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.