A few weeks back I was giving the Astra it's monthly 'battery charge up' run, and about 30miles from home the dash lit up like I'd hit the jackpot and the engine died Luckily I had just enough momentum to coast to a handily placed lay by.
Ignition off, and back on again, and it started but I had my very first EML in 6 years of owning the car.
Anyway I shifted my scangauge to code reader mode, noted the number and cleared it. The light went out, so I set gingerly off on my journey and all seemed well, and has remained so ever since
After getting back home I googled the code (160 and found the ECU had registered an internal fault.. which I now put down to being a gremlin.
Now assume I didn't have a scan gauge. The permanent light would have prompted me to get it checked out... so most prob a trip to a dealer (or other garage) , who no doubt would have charged me for the hook up and then delight in telling me my ECU was fubared, and sell me a new one... all money that I didn't need to pay out in this instance
so thank you scangauge... in one go, you've paid for yourself several times over