Note: B13-B24 on the K20Z3 typically contain O2 heater circuits and fuel pump relay control (Fuel Pump – Pin B23 – White/Black).
Before we look at the pins, you must understand that the K20Z3 uses a specific generation of Honda electronics. It sits between the early K20A (RSX Type-S) and the later 9th-gen K24Z7. The ECU of choice is the series (typically RRB-A11 or RRB-A12 for USDM).
| Pin | Wire Color | Function | Notes | |-----|------------|----------|-------| | A1 | Blk | Power Ground (GND) | Sensor/ECU ground | | A2 | Blk | Power Ground (GND) | Injector/ignition ground | | A3 | Blk | Power Ground (GND) | Shield ground | | A4 | Blk | Power Ground (GND) | Main ground | | A5 | Red/Wht | +12V Battery (Backup) | Constant power | | A6 | Yel/Blk | +12V Ignition (Main Relay) | Switched power | | A7 | Brn/Yel | Injector #1 (Cyl 1) | Peak-and-hold driver | | A8 | Brn/Blu | Injector #2 (Cyl 2) | | | A9 | Brn/Red | Injector #3 (Cyl 3) | | | A10 | Brn | Injector #4 (Cyl 4) | | | A11 | Blu/Blk | Ignition Coil #1 | | | A12 | Yel/Blk | Ignition Coil #2 | | | A13 | Red/Blk | Ignition Coil #3 | | | A14 | Wht/Blk | Ignition Coil #4 | | | A15 | Grn/Yel | VTEC Solenoid Valve | 12V output | | A16 | Grn/Red | VTEC Oil Pressure Switch | Input (ground when oil pressure OK) | | A17 | Blk | Ground for sensors (sensor return) | | | A18 | Pur/Wht | Fuel Pump Relay Control | Ground-side switching | | A19 | Wht/Red | Alternator FR (Field Control) | Alternator duty signal | | A20 | Blu/Red | Alternator C (Control) | Alternator command | | A21 | Red/Blu | Power Steering Pressure Switch | | | A22 | Grn/Wht | Radiator Fan Relay | Low speed | | A23 | Grn/Blk | A/C Clutch Relay | | | A24 | Blu | Brake Pedal Position Switch (input) | For cruise/VSA | | A25-A32 | Various | Not used or spare on some models | Check factory diagram | k20z3 ecu pinout
If the radiator fan doesn't work after a swap, you may need to enable "Use Primary Coolant Sensor" in FlashPro/KTuner.
Have a specific pin you’re struggling with? Check continuity to ground and never assume a wire color is universal—alwaysverify with a multimeter against the pins listed above. Note: B13-B24 on the K20Z3 typically contain O2
RPM and Vehicle Speed Signal (VSS) are typically found on the A connector for aftermarket devices.
The ECU is paired to a specific pedal part number: (06-08 Si) or 37950-SVB-A03 (09-11). Using a Civic LX pedal will cause APP sensor mismatch and immediate limp mode. The ECU of choice is the series (typically
If you are deep into the world of Honda performance, the code needs no introduction. Found under the hood of the 2006–2011 Honda Civic Si (FG2/FA5), this engine is a masterpiece of naturally aspirated engineering. With its high-revving 8,000 RPM redline, factory LSD, and aggressive cam profiles, it’s a favorite for tuners, swappers, and track-day enthusiasts.
If you swap a K20Z3 into a non-Honda or older Honda, the stock ECU will kill fuel and injectors unless you: