: Identify the number of plugs (e.g., 2-plug, 3-plug, or 4-plug) and the pin count per plug to match with online databases like Lextreme or ToyoDIY.
Toyota ECUs trigger the fuel pump relay through the FC pin once they sense a cranking speed via the NE sensor. If FC isn't wired correctly to your chassis relay, the pump will run only while cranking ( STA ) and cut out the moment you release the key. Eratic Idle or "Limp Mode"
Look for the on the ECU case label:
Found on legendary engines like the 4A-GE 20V, early 1UZ-FE, and non-VVTi 1JZ/2JZ platforms. These configurations typically use three distinct yellow or grey high-density connectors. The 4-Plug and 5-Plug Multi-Row Era (Late 90s - 2000s) toyota 89661 ecu pinout
Usually features 2 to 3 rows of pins spread across 2 or 3 distinct yellow plastic connectors (e.g., 10px24px18p).
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Because miswiring an ECU can permanently destroy its internal circuit board, never guess a pin's function. Use this systematic approach to find the verified diagram: : Identify the number of plugs (e
Ultimate Toyota 89661 ECU Pinout Guide: Wire Your Engine Right
Proper pinout documentation is critical for engine swaps. Many forums report successful swaps using 89661 ECU pinouts, including , where the owner found the VSS pin for speedometer to fix transmission shifting.
Identifies the component as a Toyota/Lexus Engine Control Unit. Eratic Idle or "Limp Mode" Look for the
This older unit often has pin labels printed directly on the circuit board inside the casing. 89661-13038 (7A-FE Engine) Features a three-connector setup: 26-pin (A) 16-pin (B) 12-pin (C) 89661-50241 (Lexus/Celsior 1UZ-FE): Uses a four-connector layout with 34, 22, 16, and 28-pin Modern Units (2015+): Typically follow a more standardized wiring scheme where: Ground (E1): Often found at pin 81 of the largest connector. Constant Power (BATT): Usually pin 1 or 20. Switched Power (IGSW): Commonly pin 4 or 28. CAN Communication: Pins for CANH and CANL are used for vehicle networking. How to Identify Your Specific Pinout Check the Casing:
If you encounter erratic TPS or Coolant temperature readings, ensure that sensor ground E2 is isolated from the chassis frame. Intermixing engine ground with sensor ground introduces voltage offsets that confuse the microprocessor.
| Pin | Function | Wire Color (typical) | |-----|----------|----------------------| | A1 | Injector #1 | Red or Light Green | | A2 | Injector #2 | Yellow or Light Green | | A3 | Injector #3 | Blue or Light Green | | A4 | Injector #4 | White or Light Green | | A5 | Ignition coil #1 | Black/Red | | A6 | Ignition coil #2 | Black/Red | | A7 | Ignition coil #3 | Black/Red | | A8 | Ignition coil #4 | Black/Red | | A9 | EGR vacuum solenoid | Red/White | | A10 | Fuel pump relay control | Blue/Red or Green/Red | | A11 | Main relay control | Yellow/Black | | A12 | +12V battery backup (constant) | White/Red | | A13 | Ground (ECU power) | Brown/White | | A14 | Ground (ECU power) | Brown/White | | A15 | +12V from main relay (switched) | Black/Yellow | | A16 | +12V from main relay (switched) | Black/Yellow | | A17 | O2 heater (front) | Black/White | | A18 | O2 heater (rear) | Black/White | | A19 | Idle air control (IAC) – open | Red/White | | A20 | Idle air control (IAC) – close | Red/Black | | A21 | VVT solenoid (if equipped) | Yellow/Black | | A22 | Cooling fan relay | Green/Black |
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