| Pin | Signal Name | Verified Function | Critical Note | | :--- | :--- | :--- | :--- | | | ECU Ground (Power) | High-current grounds for injectors | Must be < 0.1Ω to battery (-) | | 4, 5 | Battery Voltage (Permanent) | Direct 12V from fuse | Always powered | | 6 | Switched 12V (after relay) | 12V from main relay | Powers logic circuits | | 14 | CAN High (J1850/KWP2000) | Diagnostic bus (if used) | 2.5 – 3.5V | | 15 | CAN Low | Diagnostic bus | 1.5 – 2.5V | | 20 | O2 Sensor Heater (Pre-cat) | Ground control for heater | ~1.2A @ 12V | | 21 | O2 Sensor Heater (Post-cat) | Ground control for heater | As above | | 22 | Lambda 1 Signal (Pre-cat) | Narrowband O2 signal | 0.1 – 0.9V oscillating | | 23 | Lambda 2 Signal (Post-cat) | Narrowband O2 signal | 0.45V steady (if cat working) | | 30 | K-Line (ISO 9141) | Diagnostic communication | 0 – 12V pulsed | | 31, 32 | Shield grounds | For sensor cables | Continuity to pin 2 (black) |
⚠️ : ME20 uses low-side switching for injectors. Do not apply battery voltage directly to these pins during testing.
With a steady hand, he connected the programmer, selecting the 4E28B mask as instructed by the ECU reset procedure . He held his breath as the status bar crawled across the screen. When the "Verified" message finally flashed green, the silence of the garage was broken by the rhythmic clicking of the relays—the old Mercedes was ready to breathe again. AI responses may include mistakes. Learn more
ME20 CONNECTOR A (55-pin): A1: Relay out | A2: Batt+ | A3: Ign+ | A4: Sen Gnd | A5: Pwr Gnd A18: CKP+ | A19: CKP- | A32: CMP | A33: TPS | A40/41: Knock A54: CAN H | A55: CAN L bosch me20 pinout verified
Ensure the vehicle battery maintains at least 12.6 volts during testing. Verified Pin Assignment Matrix
Note: View is looking at the of the ECU connector (pins facing you, latch on top).
| Pin Number | Signal Name | Description | | --- | --- | --- | | 10 | VSS | Vehicle speed sensor | | 20 | PTO | Power take-off sensor | | Pin | Signal Name | Verified Function
: Fuel Injector Cylinder 1 Control — Switched ground circuit.
After cross-referencing Bosch technical documents (ESI[tronic]), OEM wiring diagrams from PSA Group, and physical continuity tests on five separate ME20.2 and ME20.4 units, .
His objective was clear: perform an procedure to bypass a stubborn immobilizer. To do it, he needed the "Holy Grail"—a verified pinout. He checked his notes one last time, referencing a worn Bosch ECU Pinout Guide . The Verified Connections He held his breath as the status bar
Turn on the switched ignition power (+12V) to Plug E Pin 2 to initiate communication with the software. Complete Plug-by-Plug Wiring Architecture Plug A: Power Supplies and Grounds
Pins for the Crankshaft Position Sensor and Oxygen (O2) Sensors are located in specific blocks to isolate signal noise.
If the internal chip has a corrupted checksum from a prior failed flash write, the K-Line may freeze. You must use boot mode to force a recovery write over the corruption. If you need help finishing your project, tell me: What vehicle make, model, and year are you working on? What specific tool or software are you using to connect?
Are you troubleshooting a , a specific sensor fault code , or performing a bench read ? Do you need the color codes for the factory wiring harness ?
Ensure your power supply maintains at least 12.2V under load. The ME2.0 drops communication if voltage falls below 11V.