If you are building a standalone ECU adapter (e.g., for a MaxxECU or Link ECU), the top-side pinout allows you to solder wires directly to the connector pins bypassing the original vehicle harness. This is common in race car conversions.
From the top perspective, with the connector facing you, the pin arrangement is typically:
Crucial note: The "Simos 33A" is often paired with the Simos 18.x software family. Many online pinouts for "Simos 18" apply directly to the 33A hardware. Do not confuse this with the older Simos 3.8 or Simos 8.5.
When an engine has a misfire, test from the top side at the connector pins: simos 33a pinout top
This is the most critical plug for bench testing. This is where the high-current power is delivered.
Tip for Bench Technicians: When bench wiring a SIMOS 33A, you must supply +12V to Pin 1 and Pin 6, with grounds on Pins 2 and 3, to establish communication with a flashing tool.
Connector Type: 60-pin rectangular (Motive / Tyco) View: Looking into the ECU connector on the wiring harness OR top side of the ECU PCB (component side). Pin numbering is mirrored if viewing from the back. If you are building a standalone ECU adapter (e
| Pin | Typical Wire Color | Function | Notes / Conditions | |-----|--------------------|-----------------------------------------------|----------------------------------------------| | 1 | Red/Yellow | Permanent battery voltage (ECU main power) | 30a, fused | | 2 | Brown | ECU ground (main chassis ground) | GND, connects to engine block / chassis | | 3 | Black/Yellow | Ignition switched power (15) | Provides +12V when key is in ON/START | | 4 | - | Not connected | | | 5 | - | Not connected | | | 6 | Grey/Red | Throttle position sensor (TPS) – signal | Linear 0-5V output | | 7 | Brown/Green | Intake air temperature (IAT) – sensor ground | Shared sensor ground | | 8 | Yellow/Black | Engine speed sensor (RPM) – signal positive | Variable reluctance sensor | | 9 | Yellow/Blue | Engine speed sensor – signal negative | | | 10 | Blue/Black | Knock sensor – signal | Shielded wire | | 11 | Green | Injector cylinder 3 – control (ground switch) | Low-side output | | 12 | Grey/White | Injector cylinder 1 – control | | | 13 | Green/Yellow | Fuel pump relay control | Activates relay (ground trigger) | | 14 | Green/White | EGR valve (if equipped) – control | PWM output | | 15 | Black/Green | Secondary air injection relay (if equipped) | Ground trigger | | 16 | White/Green | Ignition coil – cylinder 1 & 4 control | Waste-spark ignition (paired) | | 17 | White/Black | Ignition coil – cylinder 2 & 3 control | Waste-spark ignition (paired) | | 18 | Brown/Yellow | Lambda (O2) sensor – heater ground | Shared sensor return | | 19 | White/Yellow | Lambda (O2) sensor – signal (bank 1) | 0-1V narrowband | | 20 | Blue/White | Coolant temperature sensor – signal | NTC sensor, voltage divider | | 21 | - | Not used | | | 22 | Brown/Red | Engine speed sensor – shield / ground | | | 23 | Blue/Grey | Injector cylinder 4 – control | | | 24 | Brown/Black | Injector cylinder 2 – control | | | 25 | Black/Grey | Idle air control (IAC / idle stepper) – coil A| Bipolar stepper motor | | 26 | Brown/White | IAC – coil B | | | 27 | Black/Blue | IAC – coil C | | | 28 | Brown/Red | IAC – coil D | | | 29 | White/Grey | MAP sensor – signal (if speed-density system) | 0-5V output | | 30 | Brown/Blue | MAP sensor – ground | | | 31 | Yellow/Grey | Oxygen sensor heater – control (ground side) | PWM driven | | 32 | Blue/Yellow | Camshaft position sensor (if equipped) – signal| Used for sequential injection (late SIMOS 33A)|
Note: Pins may be arranged on two rows (1-16, 17-32) or (1-20, 21-40) depending on plastic housing revision.
Below is the Simos 33A pinout top view for the main 154-pin connector. This table lists pins visible from the top side when the connector is unmated from the ECU and facing upward. From the top perspective , with the connector
| Pin | Signal Name | Function | Typical Color (OEM) | |------|----------------|------------------------------------|------------------------| | A1 | BATT+ | Main battery voltage (30) | Red / Red-Blue | | A2 | BATT+ | Main battery voltage (30) | Red / Red-Blue | | A3 | BATT+ | Main battery voltage (30) | Red | | A4 | GND | Power ground | Brown / Black | | A5 | GND | Power ground | Brown | | A6 | GND | Power ground | Brown | | A7 | 15_IGN | Ignition switched power (15) | Green-Black | | A8 | 87_WU | Relay output (main relay) | Red-Yellow | | B1 | INJ_1 | Injector cylinder 1 | Yellow | | B2 | INJ_2 | Injector cylinder 2 | White | | B3 | INJ_3 | Injector cylinder 3 | Blue | | B4 | INJ_4 | Injector cylinder 4 (if 4-cyl) | Violet | | B5 | IG_A | Ignition coil A (cyl 1 & 4) | Green | | B6 | IG_B | Ignition coil B (cyl 2 & 3) | Green-Yellow | | C1 | O2_11 | Lambda sensor 1, bank 1 (pre-cat) | Black / Gray | | C2 | O2_12 | Lambda heater ground | White / Brown | | C3 | O2_21 | Lambda sensor 2, bank 1 (post-cat) | Gray | | C4 | TPS_5V | Throttle position sensor 5V ref | Orange | | C5 | TPS1_SIG | TPS signal (main) | Orange-Black | | C6 | TPS2_SIG | TPS signal (redundant) | Orange-Red | | D1 | CAN_H | CAN bus (high) | Orange / Yellow | | D2 | CAN_L | CAN bus (low) | Orange / Brown | | D3 | K_LINE | K-line diagnostic (ISO 9141) | Purple | | D4 | CKP_SIG | Crankshaft position sensor signal | Shielded pair (Blue/White) | | D5 | CMP_SIG | Camshaft position sensor signal | Shielded pair (Green/White) | | D6 | ECT_SIG | Engine coolant temperature sensor signal | Brown-Red |
📌 Note: This table shows the most common assignments for a 4-cylinder Simos 33A. V6 or diesel variants may have different pinouts. Always check your specific OEM documentation.
If diagnostic tools cannot connect: