Check the driver-side lower dash first to locate the primary electrical module and confirm each circuit using the printed label on the cover before replacing any blown link. Match amperage ratings exactly, as installing a higher-rated element can damage wiring and control units.
The cabin unit typically handles lighting, infotainment, power windows, and climate controls, while the engine compartment assembly manages ignition, cooling fans, ABS, and charging circuits. Use a test light or multimeter to verify continuity rather than relying only on visual inspection, since some links fail without visible breaks.
Remove the protective cover carefully and inspect the legend printed inside it. Each slot is numbered and tied to a specific system, allowing quick tracing of faults such as inoperative headlights, non-working outlets, or intermittent starting issues. Always disconnect the battery before working on high-current sections under the hood.
2017 Lexus IS300 Fuse Box Diagram Locations and Circuit Guide
Locate both electrical distribution units first, then cross-check each slot number with the cover legend before removing any protective link. Always pull components using a plastic extractor to avoid damaging terminals and verify amperage ratings stamped on top.
The interior assembly sits near the driver-side kick panel and contains circuits for cabin electronics, including audio system, interior lighting, and power accessories. The engine compartment unit, positioned near the battery, manages high-load systems such as ignition coils, radiator fans, and brake control modules. Each slot is mapped to a specific system, allowing quick fault tracing when a device stops working.
Use this quick reference for common circuit identification:
- Low-profile 10A slots – interior lights, infotainment memory
- 15A–20A slots – power outlets, wipers, accessory sockets
- 30A and above – blower motor, ABS, cooling fans
- Relays – starter control, fuel pump activation, headlight switching
Check continuity with a multimeter instead of relying on visual inspection, as internal breaks may not be visible. If multiple systems fail at once, inspect shared power lines and main distribution links under the hood before replacing individual components.
How to Identify Each Fuse and Relay Function in 2017 Lexus IS300
Read the cover legend inside each electrical unit and match the slot number with its labeled system before removing anything. Use the printed amperage value and position index to confirm the exact circuit tied to each protective element or switching module.
Interior circuits are grouped by function, with lower-rated components assigned to lighting, multimedia memory, and control switches, while mid-range ratings handle power windows, seat adjustment, and accessory outlets. Under the hood, higher-rated elements supply ignition coils, cooling fans, braking electronics, and charging systems. Each relay is identified by a symbol or code that corresponds to switching roles such as starter engagement or fuel delivery.
Check the color coding and stamped numbers on each piece, since manufacturers use consistent formats: small transparent units for low-current lines and larger opaque ones for high-load systems. If unsure, test with a multimeter by probing both terminals; a working part shows continuity, while a failed one reads open.
Trace faults by isolating the affected system first, then locating its assigned slot using the legend. Replace only with identical ratings and verify operation immediately after installation to confirm the issue is resolved without affecting adjacent circuits.