E46 M3 highway shutdown: tach/speedo drop, DME unreachable afterward

[sapote]

Take that with a grain of salt, the DME doesn't have a good way to tell if the relay has a ground fault.

Truth.
I remember the pump driver chip has some limited diagnosis capability, but obviously the wiring of the relay I posted above shows no pin for the DME to read the chip status.

I wonder why pin5, the load current sensing status that DME can't read, was connected on the pcb that the OP posted, shows below:

[terra]

I would suspect it was used during the development phase and might possibly still be connected to one of the unused relay pins

[sapote]

Where do I go next? I checked the fuses in the DME relay, and they test fine. Ground wires look fine to me. I cleaned the contacts.

When engine failed to run, remove the back seat and feel if the pump is running during pump priming-time with key turned to ON (it hard to hear or feel during cranking but you can try that).
Btw, with key turned ON, measure the voltage from relay pin7 to batt negative post and it should be close to 0v, if higher than 2v then it has a bad gnd. This is a better way to check for bad GND compared to using Ohmmeter and measure the resistance from pin7 to GND.

[BRiley]

Thank you all. So I replaced fuse 54 with a new one. It will crank and drive fine for a while. When I turn it off after, it takes 3 tries to crank. I have INPA, but I don't know how to log data with it. How do I capture the log? I know how to view these numbers in real time.

Also, FWIW I can activate the pump reliably with INPA. I cleaned the pump contacts last night. There is no burned wiring or anything.

I do hear the pump priming when I turn the key to position 2 for the first time. If I turn it off, and then back on to position 2, no prime. Tried this 3x, and it only primes once. I can hear it running when I try to start the car. But no start.

Pin 7 to ground is .1-.2 mV.

Thank you so much!

[sapote]

I have INPA, but I don't know how to log data with it. How do I capture the log?

inpa cannot log the file. I suggest to get OBDFusion app for phone, and the OBD reader VeePeak

https://www.amazon.com/Veepeak-OBDCheck-Bluetooth-Diagnostic-Supports/dp/B073XKQQQW/ref=sr_1_1?adgrpid=185642952239&dib=eyJ2IjoiMSJ9.aNpakUcyJbfKXQor4XWL6XByQQ_18ByfFZWf2csfPzkiST9NgXJU_78LQzz76AXxBp-UJ3hsRhur_PqWtQtamEtWhmbUyuivkfJEpaZ38pvoE2ACpBoijgsaCM0N0PhVPz--_LyfXtEv7MkcOsfmRPZ0hyyGcvunct4CCvinKCUqJer8K8xG7BHr8aENGvbga8NBe7xiQt8ms76zygzr8LrBnlKr7J6403IRmVkuHbU2daZz09Q_uxoGQXA3QquW4r1TxpbE7boh6MKIBUh9LmNICarJkwZNT3bYDGaLmT8.vvGrEgdPeM8pPha_AoaV46_vwuABscgECceQ0CFvQ3o&dib_tag=se&hvadid=792739681894&hvdev=c&hvexpln=0&hvlocphy=9031191&hvnetw=g&hvocijid=12512382691118084505--&hvqmt=e&hvrand=12512382691118084505&hvtargid=kwd-378284819021&hydadcr=6396_13571838_2418555&keywords=veepeak+obd&mcid=276ec210dc1f300e91254977142169e4&qid=1778095951&sr=8-1

[BRiley]

I think I've blown up the EWS at this point trying to crank it so many times. Working on trying to clear this ECU_NOT_RECOGNIZED error now before I can log any data.