Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1994 Lexus SC 400FACTORY OEM SERVICE PROCEDURE
Connecting Tachometer
CAUTION:
Ensure tachometer is compatible with ignition system. DO NOT allow tachometer terminal (IG-) to become grounded, as it could result in damage to ignitor and/or ignition coil.
Connect tachometer between chassis ground and terminal IG- of DLC No. 1. See Figure. See COMPONENT LOCATIONS .
COMPONENT LOCATIONS
| Component | Location | |
|---|---|---|
| Air Intake Chamber | On top center of engine, bolted to intake manifold. | |
| AM2 Fusible Link (30-Amp) | Forward of left front strut tower, in fuse/relay block. | |
| Camshaft Sensors | One on each distributor housing. | |
| Cold Start Injector | On bottom of air intake chamber. See Figure. | |
| Cold Start Injector Time Switch | Above water inlet (where lower radiator hose is attached to engine). See Figure. | |
| Crankshaft Sensor | To left of crankshaft pulley. | |
| Data Link Connector (DLC) No. 1 | Near left front corner of air intake chamber. See Figure. | |
| EFI Fuse (30-Amp) | Forward of left front strut tower, in fuse/relay block. | |
| EFI Main Relay | Forward of left front strut tower, in fuse/relay block. | |
| EGR Temperature Sensor | On left side of air intake chamber, on bottom of EGR valve adapter. | |
| EGR Vacuum Modulator (Except Calif.) | Forward of EGR valve. See Figure. | |
| EGR Vacuum Switching Valve | At left rear corner of air intake chamber. | |
| EGR Valve | On left side of air intake chamber. | |
| Engine Control Module (ECM) | Under right front floor mat and protective cover. | |
| Engine Coolant Temp. (ECT) Sensor | On water inlet, where lower radiator hose is connected to engine. | |
| EVAP (Charcoal) Canister | In right rear corner of engine bay. | |
| EVAP Check Valve | At end of hose that is connected to bottom of EVAP canister. | |
| EVAP Vacuum Switching Valve (VSV) | On right side of right cylinder head, near front. | |
| Fuel Filter | Under vehicle, forward of left rear wheel. | |
| Fuel Pressure Pulsation Damper | On rear end of left fuel rail. | |
| Fuel Pressure Regulator | On front end of right fuel rail. | |
| Fuel Pressure Regulator Vacuum Switching Valve (VSV) | On top of engine, at left front corner of air intake chamber. | |
| Fuel Pump | In fuel tank (pump is accessible with rear seat back removed, but electrical connector is accessible through luggage compartment). | |
| Fuel Pump Connector | In luggage compartment, behind rear seat back. | |
| Fuel Pump ECU | Under left rear window, behind trim panel (remove seat for access). | |
| Idle Air Control (IAC) Valve | On front end of air intake chamber. | |
| IGN Fuse (7.5-Amp) | Behind left side of instrument panel, in fuse block. | |
| Ignitors No. 1 & 2 | At left front strut tower. | |
| Ignition Coils | One to left of each distributor. | |
| Ignition Main Relay | Forward of left front strut tower, in fuse/relay block. | |
| Intake Air Temp. (IAT) Sensor | Part of Volume Airflow (VAF) sensor. | |
| Knock Sensors | Under intake manifold, on top of cylinder block. | |
| Oxygen Sensor | ||
| Main | One in each exhaust manifold. | |
| Sub (Calif.) | One downstream of each pre-catalytic converter. | |
| Park/Neutral Position (PNP) Switch | On left side of transmission, near front. | |
| PCV Valve | On top of left valve cover. | |
| Starter Relay | Forward of left front strut tower, in fuse/relay block. | |
| ST Fuse (7.5-Amp) | Behind left side of instrument panel, in fuse block. | |
| Sub-Throttle Actuator Motor (With TRAC) | On throttle body. See Figure. | |
| Vehicle Speed Sensor (VSS) No. 1 | On right side of transmission (do not confuse with VSS No. 2 on left side). See Figure. | |
| Volume Airflow (VAF) Sensor | In intake air hose. | |
Factory Service Tools
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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.
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