| Pin # | Description | | --- | --- | | 16 | Idle Air Control (IAC) Valve | | 17 | Fuel Pump Control (FPC) | | 18 | A/C Compressor Control (A/C) | | 19 | Fan Control (FC) |
: Constant 12V power directly from the battery (used for memory storage). E01 and E02 : Main power grounds for the computer. E1 : Computer ground terminal. Critical Sensor Inputs toyota 4afe ecu pinout
The 4A-FE is a speed-density fuel injection system, meaning it calculates fuel based on engine speed (RPM) and intake air density. The pinout routes three primary sensors to the ECU. First, the (AFM) or Manifold Absolute Pressure (MAP) sensor, depending on the revision—early 4A-FE engines use a flapper-door AFM (pin VG or KS), while later versions use a MAP sensor (PIM pin). Second, the Engine Coolant Temperature (THW) sensor, a thermistor whose varying resistance tells the ECU when to enrich the mixture for cold starting. Third, the Throttle Position Sensor (TPS) (IDL, VTA pins), which signals idle, part-throttle, and wide-open-throttle. Additional inputs include the Oxygen Sensor (OX1), whose narrow-band signal cycles between 0.1V and 0.9V to enable closed-loop fuel control, and the Distributor pickups (Ne and G signals), which provide crankshaft position and engine speed. | Pin # | Description | | ---
: Ignition Feedback signal sent from the igniter back to the ECU to confirm a spark occurred. Critical Sensor Inputs The 4A-FE is a speed-density
If you own a pre-1992 4A-FE, your ECU pinout will differ significantly. Do not use the pinout above for a 1989 Corolla.
– Especially pin A11 (G-) and A12 (IGt). The distributor signal wires become brittle near the ECU plug.