If your engine isn't running correctly, use a multimeter at the ECU harness: With the key ON, you should see 12V at +B .
, these are the most critical pins you will need to identify for basic engine operation: Switched ignition power (12V). Constant battery power for memory. E01 / E02: Computer grounds, usually connected to the engine block. Igniter signal (controls the firing of the ignition coils). #10, #20 (or #1, #2, #3, #4): Fuel injector signals. NE+ / NE-: Crankshaft position sensor signals. Camshaft position sensor signals. THA / THW: Intake air and coolant temperature sensor inputs. Troubleshooting Tips
Fuel injector trigger wires. Early 3S-FE models use batch-fire injection (two pins), while later models use sequential injection (four pins).
While exact pin locations vary by model year, the following matrix represents a typical mid-90s distributor-type 3S-FE ECU configuration: Connector Type Function Description Wire Color (Typical) Fuel Injector Cylinder 1 & 3 Control White/Blue Fuel Injector Cylinder 2 & 4 Control Ignition Trigger Output Black/White Ignition Feedback Confirmation Yellow/Green Power Ground 1 Power Ground 2 Plug B (16-Pin) Switched 12V Power Input Auxiliary Switched 12V Power Constant 12V Memory Power White/Blue Circuit Opening Relay (Fuel Pump) Main ECU Chassis Ground Plug C (22-Pin) 5V Sensor Reference Power Blue/Yellow MAP Sensor Signal Input Green/White Throttle Position Signal Yellow/Blue Engine Coolant Temp Signal Green/Black Intake Air Temp Signal Yellow/Black Engine RPM Speed Signal Sensor Ground Return Brown/Black Step-by-Step Troubleshooting with an ECU Pinout 3s-fe ecu pinout pdf
Constant 12V power from the battery (used for memory/diagnostic codes).
What is the of the vehicle you are working on to help identify the exact connector layout? Comparing Megasquirt PIN by PIN 3SFE and 3SGTE
: Provide expected voltage values at each pin for diagnostic testing. If your engine isn't running correctly, use a
Signal from the Intake Air Temperature (IAT) sensor.
For detailed schematics and terminal voltage values, you can find full documentation on platforms like Scribd's 3S-FE ECU Pinout for RAV4 or technical community guides on ToyotaNation
: A concise guide for the 1995–1997 2.0L 4-cylinder RAV4. E01 / E02: Computer grounds, usually connected to
at the main ECU harness or sensor plugs (TPS, O2, coolant temp). If you need to remove wires from the connector, you must lift the plastic locking tab with a flat-head tool before pulling the wire from the back. 3sfe 3sge Wiring Diagrams | PDF - Scribd
According to technical guides on Scribd and JustAnswer , key signals include:
Handles critical signals such as the Start signal (STA) , Injectors (1 and 3) , and diagnostic connections like TE1 .
The view looking directly at the metal pins protruding from the ECU housing.