[hardtailer]

Probes (1:1) are identical on A0 and A1. I needed to reduce the scale to 0.2V/div for PSEN to see what is shown. I didn't think anything of it but now you mention it, psen should be between 0 and 5V right?

Can't tell you why there are spikes on rst line.

The eprom (my bad for calling it eeprom) is a nmc27c256bq and has worked in the past but I haven't used it in the car recently.
The jumpers are set identically and correct (on both DME's) for use with this eprom.

Dave! Good to have you too here!
Indeed, I do not always understand what you're implying with an answer that is just one or two sentences long, as my knowledge is too limited.

The thing is, I'm waiting for parts to arrive and in the mean time I'm posting the results to the suggested next steps. Unfortunately each result leads to my new questions. I understand that it is hard to answer them, not watching me and therefore no way of recognising I'm doing something wrong in the process but it would be great to receive an explanation nonetheless.
I agree there is no need to rewrite any code, I'm just curious to see if I can use the logic analyzer to identify what parts exactly needs to be replaced.
Based on the almost not existing PSEN signal, I reckon it is at least the eprom. Can and will you confirm?

Surely you remember that I have replaced all ICs (and have mentioned it earlier) for brand new ones as well as the eprom from the working DME but even immediately after I still was not getting the ICV output on uC pin 5.