Simos 33a Pinout Top May 2026
When you remove the lid of a Simos 33A ECU, the top side reveals the following key landmarks:
The connector has 4 rows (A, B, C, D) with 15 pins each.
Sometimes you don't have a pinout table. Using the top view of the PCB, you can identify critical connections with basic tools. simos 33a pinout top
| Pin | Function | Signal Type | Notes | |-----|----------|-------------|-------| | 1 | Ignition coil output (cyl 1) | Output | Low side driver | | 2 | Injector output (cyl 1) | Output | Saturation driver | | 3 | Injector output (cyl 2) | Output | | | 4 | Injector output (cyl 3) | Output | | | 5 | Injector output (cyl 4) | Output | | | 6 | Fuel pump relay control | Output | Grounds relay coil | | 7 | Lambda probe heater (front) | Output | Ground side | | 8 | Throttle valve position sensor (TPS) ground | Sensor Ground | | | 9 | TPS signal (wiper) | Input | 0.5-4.5V | | 10 | TPS 5V supply | Output | +5V reference | | 11 | Intake air temp (IAT) signal | Input | | | 12 | Coolant temp (ECT) signal | Input | | | 13 | MAP sensor signal | Input | Manifold absolute pressure | | 14 | MAP sensor 5V supply | Output | | | 15 | MAP sensor ground | Sensor Ground | | | 16 | Ignition coil output (cyl 2) | Output | | | 17 | Ignition coil output (cyl 3) | Output | | | 18 | Ignition coil output (cyl 4) | Output | | | 19 | +12V main relay output | Power | To sensors/actuators | | 20 | +12V permanent (battery) | Power | Direct from battery | | 21 | +12V from main relay | Power | ECU main supply | | 22 | Ground (power) | Ground | High current | | 23 | Ground (power) | Ground | High current | | 24 | Ground (sensor) | Sensor Ground | | | 25 | CAN High (if equipped) | Comm | Drivetrain CAN | | 26 | CAN Low (if equipped) | Comm | | | 27 | Knock sensor 1 signal | Input | | | 28 | Knock sensor 2 signal | Input | | | 29 | Crank position sensor (CKP) signal | Input | 60-2 wheel | | 30 | CKP sensor ground | Shield/Ground | | | 31 | Cam position sensor (CMP) signal | Input | Hall effect | | 32 | CMP sensor supply | Output | +5V or +12V | | 33 | CMP ground | Ground | | | 34 | Lambda probe signal (front) | Input | 0-1V narrowband | | 35 | Lambda probe ground (front) | Ground | | | 36 | Vehicle speed sensor (VSS) | Input | | | 37 | Brake light switch signal | Input | | | 38 | Clutch switch signal | Input | | | 39 | A/C request signal | Input | | | 40 | A/C compressor enable | Output | | | 41 | EPC warning lamp | Output | | | 42 | Check engine lamp (MIL) | Output | | | 43 | Diagnostic K-line (ISO 9141) | Comm | | | 44 | Idle air control (IAC) - close | Output | Stepper motor coil | | 45 | Idle air control (IAC) - open | Output | Stepper motor coil | | 46 | EVAP purge valve control | Output | | | 47 | Secondary air injection (SAI) relay | Output | | | 48 | Oxygen sensor heater (rear) | Output | If present | | 49 | Idle air control (IAC) - coil B | Output | | | 50 | Idle air control (IAC) - coil A | Output | | | 51 | Not used | - | | | 52 | Not used | - | | | 53 | +12V switched (e.g., from alternator) | Input | Load signal | | 54 | Power ground | Ground | | | 55 | Power ground | Ground | | | 56 | Sensor ground | Ground | | | 57 | Ignition switch input (Terminal 15) | Input | +12V when key ON | | 58 | Start signal (Terminal 50) | Input | +12V during cranking | | 59 | Engine speed output (to tachometer) | Output | Low side driver | | 60 | +12V backup (for adaptive memory) | Power | Permanent |
Before trying to communicate with the ECU, you must power it up correctly on the bench. When you remove the lid of a Simos
Pro Tip for Bench Testing: When powering the SIMOS 33A on a bench, you need to supply Terminal 30 (12V+) and Terminal 15 (Ignition 12V+), along with a solid **Ground
This is the most critical plug for bench testing. This is where the high-current power is delivered. Before trying to communicate with the ECU, you
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.