A: The ignition signal from the ECU to the igniter is often labeled IGT (sometimes marked as IGT or IGT1). The feedback wire from the igniter is IGF . The color of the IGT wire varies but is often white or yellow. You can use a multimeter on these pins to check for a signal when cranking.
+12V input from ignition switch crank position to enrich starting fuel. Speed Sensor Input
Input from the Intake Air Temperature (IAT) sensor located in the intake piping. toyota 4afe ecu pinout
The 4A-FE system, particularly the OBD-I (earlier models) and OBD-II (later models), typically uses a multi-plug configuration.
The main ground wire bolted directly to the intake manifold or engine block. A: The ignition signal from the ECU to
: Switched 12V power from the ignition switch via the EFI main relay.
This guide provides a deep-dive into the 4AFE ECU pinout, covering connector types, sensor functions, common pin failures, and how to use this information for diagnostics. You can use a multimeter on these pins
Camshaft position positive signal.
: Idle switch signal from the TPS to tell the ECU the throttle is closed. : Speed sensor signal from the instrument cluster. ⚠️ Important Wiring Considerations Generation Shifts
If the engine cranks but won't start, back-probe the IGT pin while cranking. You should see a pulsing voltage. If IGT is pulsing but you have no spark, the igniter or ignition coil is bad. If IGF is missing, the ECU will cut fuel injector firing after approximately 2 to 3 seconds as a safety mechanism.