Ground on DME went bad

I

igeak691

Member
One of the grounds on my DME/ECU went bad, leading to the DME not tripping a relay. What's my best bet in terms of tracing the damage to see if it can be repaired? Or is my only option replacing the DME and getting it coded ($1,000+)
 
It was like that when I bought from previous owner. The service engine soon light was on because it wouldn't fire up the secondary air pump relay. Most people trace issues to either the pump itself, the air valve, a fuse, or the relay. I checked all those, and have come to the conclusion that the relay isn't being triggered by the DME which provides a ground in order to trip it. So I'm looking to trace the ground for the relay to see if I can fix it somehow without replacing the entire DME.
 
Anyone?

Opened up the box today to see what the DME is like.. just looks like a big mess of wiring. I'm pretty handy but I don't know if this is a job I can handle. Is there anything I have to be aware of when removing my DME? I'd like to check all the brown wires (ground connections) to see if any are damaged.
 
Isn't it more likely to be a fault with the DME than the actual wiring. Probably like the locking issue where the relays fail in the GM5 module.
 
Is there any danger in removing the DME to look at the insides (at the traces, etc)? I would hate to remove the DME to inspect it only to have even more issues when putting it back in.

From what I've gathered, the DME just provides the ground, so perhaps there's a trace that is blown on the DME
 
It does more than just supply an earth, which I would think is the one thing it doesn't do. Most things earth to the cars body.

I would hazard a guess that the circuit board could be multi layer making tracing a nightmare.

http://www.bmw.com/com/en/insights/technology/technology_guide/articles/digital_motor_electronics.html?source=categories&article=digital_motor_electronics
 
Well from my understanding of the DME, in terms of the secondary air system, when it wants to activate the pump, it grounds the relay, which allows current to flow through and trip the relay, giving full power to the secondary air pump. Right now, my secondary air pump is not being tripped.. I'll have to look into it further and manually ground it while the car is on and see if it gives power to the pump. If it does, it'll show that the DME is at fault and not giving a ground for the relay when needed.
 
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