A very specific topic!
| Pin | Connector | Signal Name | Description | Typical Function | |------|-----------|----------------|--------------------------------|--------------------------| | 1 | A | Ground | Sensor ground | - | | 2 | A | EVAP Canister Purge Valve (N80) | Duty cycle control | Emissions | | 3 | A | Ground | Power ground for injectors/coils | - | | 4 | A | +12V Battery | Permanent power (Terminal 30) | ECU memory | | 5 | A | +12V Switched (Terminal 15) | Switched via ignition | Wake-up signal | | 6 | A | CAN-High | Drivetrain CAN bus | ABS, Instrument cluster | | 7 | A | CAN-Low | Drivetrain CAN bus | ABS, Instrument cluster | | 8 | A | Brake light switch signal | Input | Brake pedal | | 9 | A | Clutch pedal switch | Input | Cruise control / starting | | 10 | A | A/C compressor request | Input | Climate control | | 11 | A | Radiator fan activation (low speed) | Output | Cooling | | 12 | A | Radiator fan activation (high speed) | Output | Cooling | | 13 | A | --- | Not used | - | | 14 | A | Alternator excitation signal | Output | Charge warning | | 15 | A | Diagnostic K-Line (ISO 9141) | Bi-directional | OBD2 communication | | 16 | A | --- | Not used | - | | 17 | A | --- | Not used | - | | 18 | A | --- | Not used | - | | 19 | A | Fuel pump relay control | Output | Activates FP relay | | 20 | A | Engine speed output (RPM signal) | Output | Tachometer cluster | | 21 | A | MIL (Check engine light) | Output | Warning lamp | | 22 | A | EPC light | Output | Electronic Power Control | | 23 | A | +5V Sensor supply | Reference voltage | For MAP, TPS, etc. | | 24 | A | --- | Not used | - | | 25 | A | --- | Not used | - | | 26 | A | --- | Not used | - | | 27 | A | --- | Not used | - | | 28 | B | Knock sensor 1 (cyl 1 & 2) | Signal input | Ignition timing control | | 29 | B | Knock sensor 2 (cyl 3 & 4) | Signal input | Ignition timing control | | 30 | B | Sensor ground (shield) | For knock sensors | - | | 31 | B | Intake Air Temp (IAT) | Signal input | Inside MAF or TMAP | | 32 | B | Engine Coolant Temp (ECT) | Signal input | Temperature compensation | | 33 | B | Shield ground | For crank/cam sensors | - | | 34 | B | MAF signal | Frequency/duty cycle | Airflow metering | | 35 | B | MAF ground | Sensor return | - | | 36 | B | G28 Engine speed (crank sensor) | Differential signal (-) | RPM base timing | | 37 | B | G28 Engine speed (crank sensor) | Differential signal (+) | RPM base timing | | 38 | B | G40 Camshaft position sensor | Hall effect signal | Sequential injection | | 39 | B | Throttle position sensor (G187) | Signal 1 (closing) | ETC | | 40 | B | Throttle position sensor (G188) | Signal 2 (opening) | ETC redundancy | | 41 | B | Accelerator pedal position (G79) | Signal 1 | Driver demand | | 42 | B | Accelerator pedal position (G185) | Signal 2 | Redundant signal | | 43 | B | MAP sensor (Integrated) | Boost pressure signal | Inside ECU case | | 44 | B | MAP sensor ground | Internal ECU | - | | 45 | B | External MAP (for some models) | Boost input (rare) | - | | 46 | B | --- | Not used | - | | 47 | C | Injector cylinder 1 | Output (ground switch) | Fuel delivery | | 48 | C | Injector cylinder 2 | Output (ground switch) | Fuel delivery | | 49 | C | Injector cylinder 3 | Output (ground switch) | Fuel delivery | | 50 | C | Injector cylinder 4 | Output (ground switch) | Fuel delivery | | 51 | C | Ignition coil 1 (power stage) | Output | Spark | | 52 | C | Ignition coil 2 (power stage) | Output | Spark | | 53 | C | Ignition coil 3 (power stage) | Output | Spark | | 54 | C | Ignition coil 4 (power stage) | Output | Spark | | 55 | C | N75 Boost control valve | PWM output | Wastegate control | | 56 | C | Idle Air Control (N71) | PWM output (if not DBW) | Idle stabilization | | 57 | C | Secondary air injection pump relay | Output | Cold start emissions | | 58 | C | Secondary air injection valve (N112) | Output | Air diverter | | 59 | C | O2 sensor heater (Bank 1, Sensor 1) | Output | Lambda heating | | 60 | C | O2 sensor heater (Bank 1, Sensor 2) | Output (post-cat) | Heating | | 61 | C | O2 sensor (Sensor 1) signal | Input (0-1V or wideband) | AFR | | 62 | C | O2 sensor (Sensor 1) ground | Ground for lambda | - | | 63 | C | O2 sensor (Sensor 2) signal | Input | Post-cat monitoring | | 64 | C | O2 sensor (Sensor 2) ground | Ground | - | | 65 | C | Fuel tank pressure sensor | Input | Leak detection | | 66 | C | --- | Not used | - | | 67 | C | --- | Not used | - | | 68 | C | --- | Not used | - | | 69 | A | +12V Switched (Terminal 15) duplicate | Redundant | Safety | | 70 | A | Ground | Power ground | High current | | 71 | A | Ground | Power ground | High current | | 72 | A | +12V Battery duplicate | Redundant main power | - | | 73 | A | +12V Battery duplicate | Redundant main power | - | | 74-121 | --- | Various unused or vehicle-specific pins | (e.g., cruise control, A/C pressure) | Check wiring diagram | me7.4.5 pinout