Murphy's law is a funny thing. The truck is virtually new, barely run-in with a previous 3000km foray to Lake Eyre and back... and a climb up into the Victorian High country.

What could go wrong as we now - finally -  head off into the real wild blue yonder? Well... an 'engine malfunction' it seems, our indestructable Troopy truck maybe not so indestructible afterall.

It's 9pm, propped outside a servo in Waurne Ponds, Geelong - only about an hour south of Melbourne.

Seems it's a numbers game.... well... numbers and one letter to be exact, according to our RACV man, who stoops in front of the driver's seat peering under the dash. He holds an electronic device in his right hand and nods. "Mmmm... it does happen." He nods again, shows us the device display - "P2121" - and asks for some paper to jot something down.

It seems the throttle position sensor thinks there's a problem, triggering the 'engine malfunction' light and the engine switching to 'limp' mode with a loss of power.

With the sensor disabled, we continue on as normal to our first overnight at lakeside Ondit, and a fitfull sleep broken by the midnight meetings of grey nomads, thoughts of what we may have forgotten and nearby Paul Kelly campfire covers... oh, and the questionable comfort of a mechanic's advice that "the throttle sensor hiccup may never happen again."