Another fun one… Peugeot Boxer 1994 running problem & no diagnostic communication. 2500RPM the engine was surging up and down the rev range. On the scope ( blue line in the picture ) was the earth for the crank sensor this had interferance / was dropping out randomly. We traced the fault back to sevral earth faults on the vehicle. This was all due to age and corrosion.
First was the chassis to gearbox strap, 2 x ECU earths on the engine block were cleaned, Battery negative cable to body work. […]