2012 Jimny exhaust problem.

Hi Mike,
Update. I think that hiss comes from the air con. I turned it on full blast an put the AC on, let it run an revved it a little, turned off and heard the hiss again. The system is also pressurized right? But is it a leak or just the sound I'm hearing as the gas flows inside the pipes? Still think I should check to see if CATs are open and not blocked, just for routine maintenance. Need to get the damn oxygen sensor out somehow. Btw, what is your average miles to the gallon? Think my little Jimny is a bit heavy on fuel.

The air conditioning shouldn't hiss either and it shouldn't be running all the time either only when you switch on in the cab, otherwise the pulley has a magnetic lock that allows it to rotate freely. Just pottering about the farm and occasionally town for food I'm getting about 32mpg, if I could go anywhere else I would expect up to 38 but I don't have knobley tyres or a lift so mine is quite good.

I can't recall the Aircon hissing, but this is the UK so it does not get used that much! It's possible you could hear the pump depressurisation as you turn the engine off, but it's not loud enough to be heard unless you are on top of it.
Like Lambert my Jimny is standard (manual), I get on average over a year 36mpg, but weekly it changes by journey type. Town work is about 32, long runs on motorway over 40mpg. It's going to change due to terrain and the way you drive, but you should be as a minimum 28 + mpg.