Crazy Gauge

[fixkick]

the j18 engine uses the hotter , newer thermostat (EPA rules) 200f , so is normal'
that is correct 270f IS overheated, (but the gun tells you it is no so is not,
but did you point the gun to the rear of heat outlet housing (ECT is mounted there)
scan tool does not lie, IT reads ECT reading, tells me the ECT bad. (rear of head) unless ect is bad you installe the wrong sensor as we see you did, (Ect IS not THE AC OVERHEAT SWITCH YOU BOUGHT)
THE ECT IS ON BACK OF HEAD TOP, AND HAS 3PINS, FOR SURE.
ect bad. STILL
also on the very tricky engine, (not this time or case) is that small hows from rear of water pump to the rear of clogs the thermostat goes WILD.
a very nasty very difficult problem to diagnose, just heads up, on this j18
see my J18 photos here.
http://www.fixkick.com/overheating.html

also , watch out for wrong ECT (OMG I NAILED THIS BINGO BUYING ON EBAY)
most stores (bad) sell G16 thermostat or ECT as soon as sidekick is said, a real pain in the ash can this is. J18 is the correct ECT
your VIN code is unique for j18,,,, and if they dont ask that ,bingo all parts are wrong. for sure.
btw rockauto.com asks for.r j18 sport. (but they dont ask for G16a or G16b so then get that wrong)

1998 Suzuki Sidekick Sport 1.8
I started getting random overheating spikes and now it is constant. I used IR temp gun and the engine is not over heating. Replaced both the temp gauge sensor and the ECM sensor. Using TorqueLite app with OBDII and it says the engine is over heating????? Gun reads 190-200 at the sensors at the back of the head??????? Scan tool says 270+????? Needle on gauge is in the red??