I’ve done all that chief and it’s still coming on,my cars a 2004 cdti so I’ve tried both methods and am stumped tbhThat’s oil change service. That controlled on dash. Hold down trip button and turn ignition on at same time. Wait till it flashes on and the dash. Then turn of ignition and remove finger off trip button. 5 10 seconds turn ignition on should be off now. You need the dash unit looking at. On there can also change the service date miles or years.
I will try this today mate and report backThat tells me something wrong with the dash. If that’s not working on both. You need to get a op com or other type that can read dash board info. Sounding like a faulty dash board. Does it make any difference if you remove the battery for awhile and then reconnect. Takes around 25 min to an hour for complete voltage to drain with battery off and with ignition on. The turn ignition off and put battery back on.