I can't get the diagnostic reader to work at all, I've checked all fuses and tried disconnecting every sensor under the bonnet that I can see but also the instrument cluster and still nothing, car won't even attempt to start, stressing me right out now, what else could it be? I've tried looking for an oxygen/lambda sensor on the exhaust or near the cat but there doesn't seem to be one.

New battery, earth going to body is fine and earth going to alternator is fine.

I am getting "Engine Malfunction" as well as the "Transmission Malfunction" messages.