Welcome to the comprehensive Bosch Motronic M3.1 engine management system reference guide! This material is an indispensable tool for owners and mechanics working on classic BMW M50 6-cylinder engines (2.0L and 2.5L) without VANOS.
On this page, you'll find a complete wiring diagram and detailed pinout for the 55-pin DME M3.1 connector (ECU X6000).
What you'll find in our Service Manual:
- Complete pinout table: Detailed description of the functions of each of the 55 DME M3.1 pins (Ignition, Ground, EKP relay, Injectors, Oxygen sensor signal, Crankshaft sensor).
- M50 Wiring Diagram (Without VANOS): Visual and text information about where each wire connects—from the ignition coils to the crankshaft position sensor.
- Diagnostic recommendations: Instructions on signal type (A/M/E), required equipment (oscilloscope, multimeter) and expected readings (Tester Display).
Use our detailed DME M3.1 pinout chart to quickly troubleshoot and ensure reliable operation of your legendary M50.
BMW DME Bosch M3.1 Pinout. Schematic Diagram
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BMW DME Bosch M3.1 Pinout. Schematic Diagram
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Bosch M3.1 Pinout
X6000
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 1 | A | EKP relay and TR signal (crankshaft reference) | EKP relay and EGS control unit torque converter clutch | Ground with superimposed engine speed signal | ON | Can only be measured with crankshaft rotating (the EKP relay does not switch if the TR signal is not applied) |
| 2 | A | Idle speed actuator | Idle speed actuator | Pulsed ground | See status monitoring | |
| 3 | A | Injection valve cyl. 1 | Injection valve (EV) 1 | Pulsed ground | Injection time ti | Ground => injector valve open, see component activation |
| 4 | A | Injection valve cyl. 3 | Injection valve (EV) 3 | Pulsed ground | Injection time ti | Ground => injector valve open, see component activation |
| 5 | A | Injection valve cyl. 2 | Injection valve (EV) 2 | Pulsed ground | Injection time ti | Ground => injector valve open, see component activation |
| 6 | M | Ground, EV output stages | Ground point | Ground | ||
| 7 | Not used | |||||
| 8 | A | Defect lamp (US only) | Instrument cluster | Ground | Comes on if emission related error code is stored, and comes on during starting | |
| 9 | Not used |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 10 | Not used | |||||
| 11 | A | Throttle valve position | EGS control unit | Pulsewidth modulated | Voltage value | Depends on throttle valve position, oscilloscope |
| 12 | E | Throttle valve potentiometer | Throttle valve potentiometer | 0.4–4.2V | Voltage value | Depends on throttle valve position |
| 13 | A | Preheating | Air mass meter | Voltage increase for approx. 0.5 sec | Signal stops 4 sec after engine stop | |
| 14 | M | Ground, air mass meter | Air mass meter | Ground | ||
| 15 | Not used | |||||
| 16 | E | Cylinder reference signal (ignition) | Cylinder reference sensor (connection B) | A/C voltage | Oscilloscope | One signal per camshaft revolution |
| 17 | A | ti measuring signal (kVA signal, fuel consumption signal) | Instrument cluster | Square wave signal | Multimeter function Pulse duration | Oscilloscope |
| 18 | Not used | |||||
| 19 | Not used | |||||
| 20 | Not used | |||||
| 21 | Not used | |||||
| 22 | Not used | |||||
| 25 | A | Ignition terminal 1 | Ignition coil 2 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 25 | A | Ignition terminal 1 | Ignition coil 3 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 25 | A | Ignition terminal 1 | Ignition coil 1 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 26 | E | Steady voltage, terminal 30 | B+ terminal point | > 10 V | Diagnosis not possible if not fitted |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 27 | A | DME main relay | DME main relay terminal 85 | Ground | ON | Diagnosis not possible if not fitted – connect jumper at relay terminal 30 and 87 |
| 28 | M | Ground for electronics and shielding the sensors | Ground point | Ground | ||
| 29 | A | Idle speed actuator | Idle speed actuator | Pulsed ground | Component activation | |
| 30 | Not used | |||||
| 31 | A | Injection valve cyl. 5 | Injection valve | Pulsed ground | Injection time ti | Ground => Injector valves open, see component activation |
| 32 | A | Injection valve cyl. 6 | Injection valve | Pulsed ground | Injection time ti | Ground => Injector valves open, see component activation |
| 33 | A | Injection valve cyl. 4 | Injection valve | Pulsed ground | Injection time ti | Ground => Injector valves open, see component activation |
| 34 | M | Ground, remaining output stages (except for ignition and EV) | Ground point | Ground | ||
| 35 | Not used | |||||
| 36 | A | Fuel evaporation control valve | TE valve | Pulsed ground | CLOSED/OPEN | Perform component activation, Ground => closed |
| 37 | A | Oxygen sensor heating | Oxygen sensor relay | Ground | ON | Ground => Heating activated |
| 38 | Not used | |||||
| 39 | Not used | |||||
| 40 | Not used | |||||
| 41 | E | Signal air mass meter | Hot wire air mass meter | 0...5 V | Load signal in ms | See status monitoring |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 42 | Not used | |||||
| 43 | M | Ground for sensors | Temperature sensor | Ground | ||
| 44 | E | Cylinder reference signal (ignition) | Cylinder reference sensor (connection A) | A/C voltage | Oscilloscope | One signal per camshaft revolution |
| 45 | Not used | |||||
| 46 | Not used | |||||
| 47 | Not used | |||||
| 48 | A | A/C compressor control | Compressor control relay | Ground | Ground => Compressor OFF | |
| 49 | Not used | |||||
| 50 | A | Ignition terminal 1 | Ignition coil 4 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 51 | A | Ignition terminal 1 | Ignition coil 6 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 52 | A | Ignition terminal 1 | Ignition coil 5 | Primary signal | Oscilloscope | Engine test, test step 05 |
| 53 | Not used | |||||
| 54 | E | > 10 V from DME main relay | Main relay terminal 87 | > 10 V | Voltage value | Perform status monitoring. Diagnosis not possible if signal not applied – connect jumper terminal 30 and 87 on relay |
| 55 | M | Ground, ignition | Ground point | Ground | ||
| 56 | E | Ignition terminal 15 | Ignition switch | > 10 V | ||
| 57 | Not used | |||||
| 58 | Not used | |||||
| 59 | A | Component voltage | Throttle potentiometer | 5 V | ||
| 60 | E | Programming voltage | Diagnostic connector | Only activated for control unit programming |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 61 | Not used | |||||
| 62 | Not used | |||||
| 63 | Not used | |||||
| 64 | E | Ignition timing intervention | EGS control unit | Ground | ON | Only active during gearshift |
| 65 | E | Drive range P/N switch | Transmission selector lever | Ground | ON | When position P/N |
| 66 | Not used | |||||
| 67 | E | Inductive pulse generator (connection B) | Pulse generator Engine speed/position | A/C voltage | Engine speed | Between Pins 67 and 68 (can only be measured with crankshaft rotating) |
| 68 | E | Inductive pulse generator (connection A) | Pulse generator Engine speed/position | A/C voltage | Engine speed | Between Pins 67 and 68 (can only be measured with crankshaft rotating) |
| 69 | Not used | |||||
| 70 | E | Oxygen sensor signal | Oxygen sensor | Pulsating voltage up to approx. 1 V | Voltage value | Can only be measured with engine running at operating temperature |
| 71 | M | Ground oxygen sensor | Oxygen sensor | Ground | ||
| 72 | Not used | |||||
| 73 | E | Road speed signal | Instrument cluster | Square wave signal | km/h | Status monitoring |
| 74 | Engine speed signal TD | Instrument cluster | Square wave signal | One signal per ignition | ||
| 75 | Not used | |||||
| 76 | Not used | |||||
| 77 | E | Intake air temperature | Intake air temperature sensor | 0...5 V | °C | Temperature-dependent |
| Pin | Type | Description/Function | Connection | Type of Signal | Tester Display | Measurement Notes |
| 78 | E | Engine temperature | Engine temperature sensor | 0...5 V | °C | Temperature-dependent |
| 79 | Not used | |||||
| 80 | Not used | |||||
| 81 | E | Drive-away protection | On-board computer | > 10 V | ||
| 82 | Not used | |||||
| 83 | Not used | |||||
| 84 | Not used | |||||
| 85 | E | Pressure signal | Pressure switch | |||
| 86 | E | Compressor signal | IHKR control unit | |||
| 87 | E | RxD diagnostic data line | Diagnostic connector | > 10 V | When cover of diagnostic connector closed | |
| 88 | E/A | TxD diagnostic data line | Diagnostic connector | Ground | When cover of diagnostic connector closed |