Is there any way to identify a dead e38?

I've triple-checked my bench harness connections, and I still can't connect to the ECM with HPtuners Scanner or with a common obd2 reader. I'm getting power and ground to all the correct pins on the ECM and the obd2 port, and I've run the 2500 and 2501 can-bus wires correctly with a 120-ohm resistor installed between the wires.

I have the "check engine" and "powertrain relay" wires grounding out LED lights, and both lights remain lit the entire time the ignition switch is on. I thought the "check engine" light would go out after several seconds, and the "powertrain relay" would cut off after a minute or two.

One last check I thought of, is to power the bench harness with a 12v battery instead of the wall-wart that I've been trying.

Is there anything else I can check before I go shopping for a replacement e38 ECM?

it needs battery power and ignition power in correct terminals and earth, when i done mine i didnt use any resistor just can-bus wires in and the 2 powers and earth and it worked fine

Definitely try a different power source. Many of those wall wart power supplies are not well regulated and don't tolerate overload very well.

Rick

Some further info--

I cut the tail off the wall wart, verified polarity, and connected that to a car battery. Nothing changed.

My brother is a GM tech, and he brought his GM MDI over to try it out. When he scoped the data wires, he saw a decent enough signal that he thought it should work. He was definitely seeing some attempted "talking" from the ECM. However, when he tried to actually read any data from the ECM, his MDI couldn't even tell there was a ECM there. He said he's never seen that. In his experience, bricked ECM's are always still readable, but the content has turned to gibberish. He also verified my connections, and confirmed everything was pinned correctly.

I'll try cleaning up my data wires, twisting them correctly, and attempting better solder joints. If that doesn't establish open communication, I'll go looking for a replacement ECM.

u dont need the resistors when talking to the ecu since it does that by acting as the end of the line.

Quote:

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Originally Posted by Tre-Cool

u dont need the resistors when talking to the ecu since it does that by acting as the end of the line.

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We removed the resistor from the circuit, and it didn't make any difference. When the resistor was in the circuit, the signal was very slightly cleaner. My brother said he's played around with removing the resistor on factory vehicles, since some of them come with an easily removable resistor. When that CAN bus is going through a long string of modules, the resistor does make a significant difference in the amount of noise on the line.