This page provides a detailed and easy-to-read pinout reference for the Bosch Motronic M1.3 engine control unit used in early BMW M20 and M40 engines. The wiring diagram clearly illustrates every ECU pin, its assigned function, and the corresponding sensor or actuator connection.
The diagram is designed to support technicians, enthusiasts, and anyone performing diagnostics, harness repairs, engine swaps, or custom wiring work. All essential circuits—including power supply, grounds, ignition control, injectors, idle control, load signals, oxygen sensor input, and diagnostic K-line—are accurately labeled and structured for quick identification.
Whether you are troubleshooting electrical issues, rebuilding an engine harness, or studying Bosch Motronic systems, this M1.3 pinout diagram provides a precise and reliable reference for professional use.
M30 with EML Wiring Diagram
DME Bosch M1.3 Pinout (E34) 1992
X6000
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 1 | A | Ignition terminal | Ignition coil | Primary signal |
Oscillos cope |
Engine test, test step 05 |
| 2 | M | Ground | Ground point | Ground | ||
| 3 | A | EKP relay and TR signal (crankshaft reference) | EKP relay and electronic transmission control unit | Ground with superimposed signal | ON | Can only be measured when crankshaft rotating |
| 4 | Not used | |||||
| 5 | A | Evaporative valve | Evaporative valve | Pulsed ground |
CLOSED/ OPEN |
Perform component activation, ground => closed |
| 6 | A | Engine speed signal | Instrument cluster | Square wave signal | One signal per tgnition | |
| 7 | E | Air flow meter signal | Air flow meter | $0...5\ V | Load signal ms | See status monitoring |
| 8 | E |
Cylinder identification sensor (ignition) |
Cylinder identification sensor (connection B) | ON/OFF | See status monitoring | |
| 9 | Not used | |||||
| 10 | M | Ground, oxygen sensor | Oxygen sensor | Ground | ||
| 11 | Not used | |||||
| 12 | A | Voltage supply, air flow meter | Air flow meter | $-5\ V$ | ||
| 13 | E | RxD diagnostic data line | Diagnostic connector | $> 10\ V$ | When cover of diagnostic connector closed |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 14 | M | Ground, injection valves | Ground point | Ground | ||
| 15 | A | Indicator "Check engine" | Instrument cluster | Ground | Comes on if emission related error code is stored, and comes on during starting | |
| 16 | A | Injection valves cyl. (1 + 3 + 5) | Injection valve | Pulsed ground | Injection time ti |
Ground Rightarrow injector valves open, see component activation |
| 17 | A | Injection valves cyl. (2 + 4 + 6) | Injection valve | Pulsed ground | Injection time ti |
Ground \Rightarrow injector valves open, see component activation |
| 18 | E | Hot at all times | Terminal 30 | $> 10\ V$ | ||
| 19 | M | Ground for electronics and sensor shields | Ground point | Ground | ||
| 20 | Not used | |||||
| 21 | Not used | |||||
| 22 | Not used | |||||
| 23 | Not used | |||||
| 24 | M | Ground, remaining output stages (except for ignition and injection valves) | Ground point | Ground | ||
| 25 | Not used | |||||
| 26 | M | Ground, air flow meter | Air flow meter | Ground | ||
| 27 | E | Ignition terminal 15 | Ignition switch | > 10\ V | ||
| 28 | E | Oxygen sensor signal | Oxygen sensor |
Pulsating voltage up to approx. 1\ V |
Voltage value | Can only be measured with the engine running at operating temperature |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 29 | Not used | |||||
| 30 | Not used | |||||
| 31 | E | Cylinder identification sensor (ignition) | Cylinder identification sensor (connection A) | ON/OFF | See status monitoring | |
| 32 | A | Measuring signal (KVA signal) | Instrument cluster | Square wave signal | Multimeter function pulse duration | Oscilloscope |
| 33 | Not used | |||||
| 34 | Not used | |||||
| 35 | Not used | |||||
| 36 | A | DME main relay terminal 85 | DME main relay terminal 85 | Ground | ON | Diagnosis not possible if not fitted, connect jumper at relay terminal 30 and 87 |
| 37 | E | U-Batt from DME main relay | Main relay terminal 87 | U-Batt | Voltage value | Perform status monitoring. Diagnosis not possible if signal not applied. Connect jumper terminal 30 and 87 on relay |
| 38 | E | Drive away protection | On-board computer | > 10 V | ||
| 39 | E | Programming voltage | Diagnostic connector | Only activated for control unit programming | ||
| 40 | Not used | |||||
| 41 | E | Auxiliary fan signal | EML control unit | 12V | ON/OFF | |
| 42 | E | Drive range P/N | Transmission selector lever switch | Ground | ON | When position P/N |
| 43 | Not used | |||||
| 44 | E | Intake air temperature | Air quantity meter | 0...5V | ^\circ\text{C} | Temperature dependent |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 45 | E | Engine coolant temp. | Engine coolant temp. sensor | $0...5\ V$ | $^\circ\text{C}$ | Temperature dependent |
| 46 | Not used | |||||
| 47 | E | Inductive pulse generator (connection A) | Pulse generator engine speed, crankshaft position | A/C voltage | Engine speed | Between Pins 47 and 48 (can only be measured with crankshaft rotating) |
| 48 | E | Inductive pulse generator (connection B) | Pulse generator engine speed, crankshaft position | A/C voltage | Engine speed | Status monitoring at or above starting rpm |
| 49 | Not used | |||||
| 50 | E | Torque cutout signal | ABS/ASC control unit | |||
| 51 | E | Ignition timing intervention | Electronic transmission control unit | Ground | ON | Only active during gear shift |
| 52 | E | Idle signal | EML control unit | Ground | ON | See status monitoring on set idle speed |
| 53 | E | Full load signal VL | EML control unit | Ground | ON | At full load (kick-down) |
| 54 | E | Torque converter clutch WK | Electronic transmission control unit EGS | Ground | ON | When WK engaged, see status monitoring |
| 55 | E/A | TxD diagnostic data line | Diagnostic connector | Ground | When cover of diagnostic connector closed |