Bench-testing BMW ECUs

Mainly ECU repair companies or chiptuners often use diagnostic tool to perform ECU diagnostics outside vehicle. This is generally possible by conntecting battery power supply (battery +), ignition, ground (earth, battery -), CAN-H / CAN-L or ISO9141 K-Line directly to ECU and OBD-II connector.

In BMW world this is a bit complicated as the vehicle has many digital communication networks (K-BUS, CAN-BUS, MOST, FlexRay) connected via gateway. OBD2 diagnostic bus (either "D-CAN" or ISO9141 K-Line) is behind such gateway.

Many older ECUs that provide ISO9141 K-Line (not K-BUS!) can be directly tested using BimCOM (Examples: DME Siemens MS4.2, DDE5 ECUs, E53 KOMBI, etc.). ECUs using K-BUS (such as EWS3 module) require gateway connected between OBD2 and ECU gateway (e.g. KOMBI instrument for E83, E46, E53, etc.). Vehicles starting E65 (E60/etc) require ZGW as gateway. ECUs from newer vehicles utilizing D-CAN also may require gateway to translate CAN speed / physical layer / IDs. Also one 120 Ohm resistor may be required between CAN-H and CAN-L lines. Despite of fact some competitive diagnostic interfaces may work without the additional resistor, it is not possible to add it to the BimCOM diagnostic interface by default as such modification is not compatible with CAN-BUS termination standard and may fail to diagnose a real vehicle.

Unfortunately we cannot respond to general questions which ECUs work on bench and how to connect them, on the other hand without any guarantee we're always happy to help knowledgeable people.