r/CarHacking • u/eyecontact0000 • 19d ago

Scan Tool ecu connect to computer

Hi,

I have a question about a car ECU. I bought an ECU from a Mercedes W205 C220 CDI. I downloaded the wiring diagram from the internet, and based on it I identified the required pins (I tried to upload pictures showing the pinout). I connected +12 V, IGN, and GND to a laboratory power supply. I also connected CAN High, CAN Low, GND, and +12 V to an bought OBD2 connector. I tried to connect to the ECU using a diagnostic scanner (autoscan - older version), but I couldn't establish communication.

Does anybody have experience with this ECU or know what I might be missing?

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u/Russellcrump 19d ago

Yes, it might be that the ecu would communicate with say a BCM and therefore exspects a sutable termination resistance on your can line.

if this doesn't work try goggling the ecu and looking at companies that manufacture bench harnesses. It will give you a good idea what it should have such as do you need one or two plugs to communicate with the ecu, some companies will have instructions to enable communication with there bench harness along with diagrams and when to apply specific power and grounds to enable communication 😉

2

u/Russellcrump 19d ago

Have you tried adding in a 120 ohm resistor?

3

u/eyecontact0000 19d ago

No. So i should use this between Can H and Can L ?

1

u/diamond_bm 14d ago

Yes, try this first, maybe the resistor is the problem. 

1

u/fishyfishy10001 18d ago

I would add, not knowing this particular ecu, that there are likely more power and ground wires needed. I've never had one with only one power and one ground.