Check One-Touch Interior Light System

WARNING: This page is about a different car, the 2021 Subaru Ascent. However, it is still accessible from the selected car via links, so may be relevant.

Trouble symptom:

Spot map lights (switch in DOOR position) and reading lights do not turn on/off even if the one-touch interior light switch is pressed.

CHECK INTERIOR LIGHT ILLUMINATION .
1. Turn the spot map light switch to the DOOR position.
2. Press the one-touch interior light switch.
Do the indicators (displayed in MET) of spot map lights, reading lights and one-touch interior light turn on/off in accordance with one-touch interior light switch operation?

Yes : The one-touch interior light switch system is normal.

No : Go to 2.

If only the one-touch interior light indicator does not turn on/off, check the LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
CHECK THE LIGHTS .
Check the spot map light and reading light.

Are the spot map light and reading light normal?

Yes : Go to 3.

No : Replace the spot map light and reading light.
CHECK CURRENT DATA .
1. Turn the ignition switch to ON.
2. Display the [One-touch All Interior Lights ON/OFF Switch Input] data using Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .
Does the display switch between [OFF] <-> [ON] when the one-touch interior light switch is operated?

Yes : Go to 5.

No : Go to 4.
CHECK SWITCH .
Check the one-touch interior light switch.

Is the one-touch interior light switch normal?

Yes : Go to 5.

No : Replace the one-touch interior light switch.
CHECK HARNESS .
1. Disconnect the connectors of body integrated unit and one-touch interior light switch.
2. Check the harness between body integrated unit and one-touch interior light switch.
  Connector & terminal
  
  (i84) No. 4 - (i374) No. 1:
Is harness normal?

Yes : Go to 6.

No : Repair or replace the harness.
CHECK HARNESS .
Check the harness between one-touch interior light switch connector and chassis ground.

Connector & terminal

(i374) No. 4 - Chassis ground:

Is harness normal?

Yes : Go to 7.

No : Repair or replace the harness.
CHECK CURRENT DATA .
1. Turn the ignition switch to ON.
2. Display the data of [Map lamp output] and [Battery Power Supply Output for Interior Lights] using Subaru Select Monitor, Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .
  - Does the display of [Map lamp output] switch between [OFF] <-> [ON] when the one-touch interior light switch is operated?
  - Is [Battery Power Supply Output for Interior Lights] [ON]?
Yes : Go to 8.

No : Check the body integrated unit and replace it if defective.
- Inspection: Ref. to BODY CONTROL (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
- Replacement: Ref. to SECURITY AND LOCKS>BODY INTEGRATED UNIT .
CHECK FUSE AND RELAY .
1. Turn the ignition switch to OFF.
2. Check F/B fuse No. 26 and O/T ILL RELAY. Ref. to LIGHTING SYSTEM>Relay and Fuse>INSPECTION .
Is the F/B fuse No. 26 and O/T ILL RELAY normal?

Yes : Go to 9.

No : Replace the defective fuse or relay.
CHECK HARNESS .
1. Disconnect the connectors of spot map light, reading light and O/T ILL RELAY.
2. Measure the voltage between each connector and chassis ground.
  Connector & terminal
  
  (B225) No. 36 (+) - Chassis ground (-):
  
  (B225) No. 34 (+) - Chassis ground (-):
  
  (R405) No. 1 (+) - Chassis ground (-):
  
  (R369) No. 1 (+) - Chassis ground (-):
  
  (R370) No. 1 (+) - Chassis ground (-):
  
  (R371) No. 1 (+) - Chassis ground (-):
  
  (R372) No. 1 (+) - Chassis ground (-):
Is the voltage 8.5 - 16.5 V?

Yes : Go to 10.

No : Repair or replace the harness.
CHECK HARNESS .
1. Disconnect the connectors of body integrated unit, spot map light, reading light and O/T ILL RELAY.
2. Check the harnesses between each light connector and body integrated unit.
  Connector & terminal
  
  (i171) No. 11 - (B225) No. 35:
  
  (i171) No. 10 - (R405) No. 4:
  
  (i84) No. 9 - (R369) No. 3:
  
  (i84) No. 9 - (R370) No. 3:
  
  (i171) No. 16 - (R371) No. 3:
  
  (i171) No. 16 - (R372) No. 3:
Is harness normal?

Yes : Go to 11.

No : Repair or replace the harness.
CHECK HARNESS .
Check the harnesses between spot map light and reading light connectors and chassis ground.

Connector & terminal

(R405) No. 13 - Chassis ground:

(R369) No. 5 - Chassis ground:

(R370) No. 5 - Chassis ground:

(R371) No. 5 - Chassis ground:

(R372) No. 5 - Chassis ground:

Is harness normal?

Yes : Check the body integrated unit and replace it if defective.
- Inspection: Ref. to BODY CONTROL (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
- Replacement: Ref. to SECURITY AND LOCKS>BODY INTEGRATED UNIT .
No : Repair or replace the harness.