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This guide details a revised in-dash kill switch for a 2022 Toyota Land Cruiser 300 Series GR Sport (diesel, RHD, Australia). An SPST switch controls an SPDT Switching Relay to interrupt the fuel pump relay control signal (from Engine ECU). When SPST is ON (normal mode), the vehicle primes and starts. When SPST is OFF (armed mode), start attempts route the ECU signal to the timer, pulsing horn and parking lights for ~10s, then stops. All components are mounted behind the dashboard (passenger side, left) for concealment. The one-shot timer relay ensures pulsing stops automatically after ~10 seconds.
Qty
Item
1
SPST micro toggle switch (10A 12V, compact, ~15x10mm; hidden in glovebox or blank button)
1
12V 30A SPDT relay (with socket, ~2.5x2.5cm; Switching Relay for ECU signal)
1
12V solid-state flasher module (compact, ~3x3cm; LED-compatible)
2
12V 30A micro SPDT relays (with sockets, ~2.5x2.5cm; for horn and parking lights)
1
12V adjustable one-shot timer relay (1-10s interval, ~4x3cm; monostable, 10s pulse)
2
Inline fuse holders (5A for flasher, 10A for timer/Switching Relay input)
8m
Automotive wire (0.5mm² for signals, 1mm² for relays)
10
Flyback diodes (1N4007; for spike protection)
1
Optional: 100Ω resistor (to mimic relay coil load and prevent ECU DTCs)
-
Solder, heat shrink, crimp terminals, split loom, electrical tape, cable ties
-
Multimeter, OBD-II scanner, trim removal tools, firewall grommet
Multimeter (voltage/continuity)
OBD-II scanner (DTC checks)
Trim removal tools
Soldering iron or crimping tool
Toyota wiring diagram (TIS or IH8MUD for LC300 diesel Engine ECU pins and fuel pump control)
SPST Switch ON (Normal Mode): Switching Relay energized; ECU signal connected to fuel pump relay coil via NO contacts. Vehicle primes and starts on button press.
SPST Switch OFF (Armed Mode): Switching Relay de-energized; ECU signal routed to one-shot timer via NC contacts. Start attempt (button press) triggers timer, which outputs a 10-second pulse to the flasher, pulsing horn and parking lights for ~10s, then automatically stops via timer’s monostable function. Pulsing occurs only on start attempts, not constantly.
The push-button start (dash-mounted) indirectly triggers the system via ECUs:
Button press (with brake) signals Certification ECU (passenger compartment, left dash) for key verification.
Verified signal goes to Engine ECU (engine bay), which outputs a momentary control signal (~1-2s, +12V or ground) to the fuel pump relay coil for priming.
This ECU signal wire is interrupted by the Switching Relay. When SPST is OFF, button presses reroute the signal to the timer input, activating pulsing only on attempts—no direct button wiring needed to avoid CAN/immobilizer issues.
Optional: Add 100Ω resistor across Switching Relay’s NO path to simulate coil load, reducing DTC risks (e.g., P0087 fuel pressure).
Locations:
Fuel Pump Relay: Engine Fuse Box 1/2 (under hood, left/right near battery; FUEL PMP, 20-30A, Engine ECU-controlled).
Horn Relay: Engine Fuse Box 1 (HORN, 15A).
Parking Lights: TAIL-related fuses (10A, engine bay or passenger fuse box, left dash; e.g., ECU-IGR NO.3).
Mounting: Behind glovebox or lower left dash (passenger side, RHD).
Connections (Revised for Swapped SPST Functions):
Identify fuel pump relay coil control wire from Engine ECU (multimeter: activates ~12V/ground on start button press with brake; confirm type—often ground-switched).
Cut coil control wire; run ECU side through firewall grommet (near steering column) to Switching Relay’s common terminal. Run relay coil side to Switching Relay’s NO terminal (normal start when SPST ON).
SPST Switch: One side to +12V ACC (10A fused, passenger fuse box); other side to Switching Relay coil (energizes relay when SPST ON for normal mode).
Switching Relay: NC terminal to timer input (routes ECU signal to timer when SPST OFF for pulsing). Ground relay coil to chassis; diode across coil (cathode to +12V).
Optional: Solder 100Ω resistor parallel to NO path.
Timer output to flasher input (10s pulse via one-shot timer).
Flasher output splits to Relay 1 (horn) and Relay 2 (parking lights) coils.
Relay 1: NO contacts pulse ground to horn control wire (splice, engine bay or Body ECU).
Relay 2: NO contacts pulse +12V to TAIL circuit (fuse tap or splice).
Diodes across all relay/timer coils (cathode to +12V).
Fuses: 10A on ACC power (for SPST/Switching Relay and timer); 5A on flasher output.
Disconnect battery (negative, engine bay, right side).
Remove dash trim: Left lower panel (passenger footwell) and glovebox.
Access engine Fuse Boxes 1/2; identify FUEL PMP, HORN, TAIL wires (diagram/multimeter—test with start button presses).
Cut fuel pump coil control wire; route ECU side through firewall (seal grommet) to Switching Relay (in-dash).
Mount SPST switch (hidden, e.g., glovebox); Switching Relay, other relays, timer, flasher behind glovebox (adhesive brackets).
Splice horn/parking light controls; protect wires in loom, away from airbag/HVAC.
Refit trim; reconnect battery.
SPST Switch ON: Press start button (with brake)—fuel pump primes (whir), engine starts. No horn/lights.
SPST Switch OFF: Press start button—cranks, no start. Horn and parking lights pulse ~10s only after button press, then automatically stop (via one-shot timer). No pulsing without button attempt.
Scan for DTCs (OBD-II, left dash); clear if needed (e.g., P0087).
Check battery drain (<50mA when SPST OFF). Test in GR Sport modes (Sport, Off-Road).
Verify concealment.
Firewall: Use existing grommet (near brake booster/steering column); seal with silicone.
Switch: Consider Toyota blank button (~$10-20 AUD, eBay) for factory look.
Compliance: Confirm pulsing horn/lights is legal (NSW RMS). Optional: Use piezo siren (~$15, Jaycar) instead of horn.
Professional Install: Recommended to avoid ECU damage (e.g., ARB, Opposite Lock).
Sources: Fuse/relay details from LC300 maintenance data; ECU control from Toyota wiring info.
These instructions are for an experienced auto electrician installing the revised in-dash kill switch system above. For clarity, the system interrupts the fuel pump relay control signal from the Engine ECU to prevent starting when the SPST kill switch is OFF (armed mode), while triggering a 10-second pulsing of the horn and parking lights on push-button start attempts. When the SPST switch is ON (normal mode), the vehicle operates normally.
Assumptions and Prerequisites:
You have access to a Toyota TIS (Technical Information System) subscription or equivalent service manual for LC300 diesel wiring diagrams (e.g., Engine ECU pinouts, fuse/relay locations). Key references: Fuel pump relay (FUEL PUMP or EFI NO.2, 20-30A) in Engine Compartment Fuse Box No.1 or No.2 (under hood, left/right near battery); horn relay (HORN, 15A) in Fuse Box No.1; parking lights (TAIL, 10A) in passenger compartment fuse box (left dash, behind lower trim).
Use standard Bosch-style 5-pin SPDT automotive relays (30/40A rating) for the Switching Relay, Relay 1 (horn), and Relay 2 (parking lights). Pinout: 30 (common), 87 (NO), 87a (NC), 86 (coil +12V), 85 (coil ground).
One-shot timer relay: Assume a standard adjustable module (e.g., 12V monostable, terminals: +12V, ground, trigger input, output).
Solid-state flasher: Standard automotive (terminals: +12V input, ground, pulsing output).
SPST switch: Simple toggle (terminals: 1 for +12V input, 2 for output to Switching Relay coil).
Tools: Multimeter (voltage/continuity/ground checks), OBD-II scanner (for DTCs), trim removal tools, soldering iron/crimps, heat shrink, wire loom, cable ties, firewall grommet sealant.
Safety: Work in a well-ventilated area. Verify all wire identifications with multimeter and wiring diagram to avoid ECU damage.
Time Estimate: 1-2 hours.
Wire Specs: 0.5mm² for signals (e.g., ECU control), 1mm² for relays/coils. Use automotive-grade wire.
Park the vehicle on a flat surface, engage parking brake, and chock wheels.
Disconnect the battery negative terminal (engine bay, right side for RHD; 12mm socket) to prevent shorts or ECU errors.
Remove lower dash trim on passenger side (left for RHD): Use trim tools to pry off the lower panel (footwell area) and glovebox (release clips, disconnect any wiring like glovebox light).
Locate key areas:
Passenger compartment fuse box: Behind lower left dash trim.
Engine compartment Fuse Boxes No.1/No.2: Under hood, left/right near battery (remove covers).
OBD-II port: Under left dash for post-install DTC scanning.
Firewall grommet: Near steering column or brake booster (left side) for routing wires from engine bay to dash.
Gather a Toyota LC300 diesel wiring diagram (e.g., from TIS). Identify:
Fuel pump relay control wire: From Engine ECU (engine bay) to FUEL PUMP relay coil in Fuse Box No.1/No.2. Typically ground-switched (ECU grounds the coil to activate); wire color often white/blue or blue/black (confirm with multimeter: ~12V at relay coil when key ON, drops to ground on start attempt).
Horn relay control wire: In Fuse Box No.1 (HORN 15A); ground-switched (black or similar; grounds coil when horn button pressed).
Parking light circuit: TAIL fuse (10A) in passenger fuse box or engine bay; +12V switched wire (often green or red/yellow; +12V when lights ON).
ACC power source: Tap a 10A-fused ACC circuit in passenger fuse box (e.g., ECU-ACC or CIG fuse; +12V with ignition ON, off when OFF).
Open engine compartment Fuse Boxes No.1/No.2 (remove plastic covers).
Locate the FUEL PUMP relay (20-30A, labeled; pull it out to access terminals).
Using multimeter:
Probe relay socket for coil terminals (low-current side; one always +12V, other ECU control).
Turn ignition ON (without starting); confirm +12V on one coil pin.
Attempt start (push button with brake); ECU control wire (white/blue typical) should ground or provide signal (~0V or pulse).
Cut the ECU control wire ~10-15cm from the relay socket (leave slack for splicing).
Label ends: "ECU side" (from Engine ECU) and "Relay side" (to fuel pump relay coil).
Route the "ECU side" wire through an existing firewall grommet (near steering column; enlarge if needed, seal with silicone) to the in-dash area (behind glovebox). Use fish tape for routing; protect with split loom.
Locate horn relay control wire: In Fuse Box No.1 (HORN); probe for ground-switched wire (grounds when horn pressed). Splice (T-tap or solder) without cutting; route extension wire (black, 1mm²) through firewall to dash if not accessible from passenger fuse box.
Locate parking light circuit: Tap TAIL fuse (10A) using a fuse tap (+12V when lights ON); or splice into control wire (green typical). Route extension wire (red, 1mm²) to dash.
Behind glovebox or lower left dash (passenger side): Secure all relays, timer, and flasher using adhesive brackets or cable ties (away from HVAC ducts, airbags, or moving parts).
Mount SPST switch in a hidden location (e.g., glovebox wall or disguised as a blank button). Ensure it's accessible but concealed.
Switching Relay (SPDT, Bosch-style pins):
Pin 30 (common): Connect to "ECU side" of cut fuel pump control wire (blue signal wire, 0.5mm²; solder and heat shrink).
Pin 87 (NO): Connect to "Relay side" of cut fuel pump control wire (blue, 0.5mm²; this path for normal start when SPST ON).
Pin 87a (NC): Connect to timer relay trigger input (blue, 0.5mm²; this path for alarm pulsing when SPST OFF).
Pin 86 (coil +12V): Connect to SPST switch output terminal (red, 1mm²).
Pin 85 (coil ground): Connect to chassis ground (black, 1mm²; use ring terminal on a clean metal point behind dash; confirm <0.5Ω resistance).
SPST Switch:
Terminal 1 (input): Connect to +12V ACC source (10A inline fuse from passenger fuse box; red, 1mm²; +12V only with ignition ON).
Terminal 2 (output): Connect to Switching Relay pin 86 (red, 1mm²; energizes relay when SPST ON for normal mode).
Optional: Solder 100Ω resistor (1/4W) parallel between Switching Relay pins 30 and 87 (across NO path) to mimic fuel pump relay coil load and prevent ECU DTCs.
Timer Relay (monostable, adjustable 1-10s; set to 10s via trimmer potentiometer):
+12V terminal: Connect to +12V ACC source (shared 10A fuse; red, 1mm²).
Ground terminal: Connect to chassis ground (black, 1mm²).
Trigger input: Connect to Switching Relay pin 87a (NC; blue, 0.5mm²).
Output: Connect to flasher module input (blue, 1mm²).
Add flyback diode (1N4007): Cathode (banded side) to +12V terminal, anode to output (protects from spikes).
Flasher Module:
+12V input: Connect to +12V ACC source (shared 10A fuse; red, 1mm²).
Ground: Connect to chassis ground (black, 1mm²).
Pulsing output: Split to Relay 1 and Relay 2 coil pins 86 (blue, 1mm²; add 5A inline fuse on this line).
Relay 1 (SPDT, Bosch-style):
Pin 30 (common): Connect to chassis ground (black, 1mm²).
Pin 87 (NO): Connect to horn relay control wire splice (black, 1mm²; pulses ground to activate horn).
Pin 87a (NC): Leave unconnected (or tape off).
Pin 86 (coil +12V): Connect to flasher output (blue, 1mm²).
Pin 85 (coil ground): Connect to chassis ground (black, 1mm²).
Add flyback diode: Cathode to pin 86, anode to pin 85.
Relay 2 (SPDT, Bosch-style):
Pin 30 (common): Connect to +12V ACC or battery source (red, 1mm²; optional 10A fuse if not using fuse tap).
Pin 87 (NO): Connect to parking light circuit splice or fuse tap (red, 1mm²; pulses +12V to activate lights).
Pin 87a (NC): Leave unconnected.
Pin 86 (coil +12V): Connect to flasher output (blue, 1mm²).
Pin 85 (coil ground): Connect to chassis ground (black, 1mm²).
Add flyback diode: Cathode to pin 86, anode to pin 85.
Protect all splices/connections with heat shrink tubing and electrical tape.
Route wires in split loom; secure with cable ties away from heat, moving parts, or sharp edges.
Seal firewall grommet with silicone to prevent water ingress.
Refit all dash trim and fuse box covers.
Reconnect battery negative terminal.
Clear any DTCs with OBD-II scanner (e.g., P0087 fuel pressure if present).
Test with SPST ON: Push start (brake depressed)—fuel pump primes (whir sound), engine starts. No horn/lights pulsing.
Test with SPST OFF: Attempt start—cranks but no fuel/run. Horn and parking lights pulse ~10s (sync with flasher rate), then auto-stop. Verify no pulsing without start attempt.
Check battery drain: Multimeter in series on negative cable; <50mA with SPST OFF and ignition OFF.
Road test: Drive in various GR Sport modes (Sport, Off-Road); ensure no interference or DTCs.
If issues: Re-check wire polarities (e.g., ground vs. +12V switched), relay pins, and timer settings. Scan DTCs and consult wiring diagram.
