The temperature gauge on my 98 Mazda 626 2L MTX recently went all wonky, most of the time it's pegged low, but sometimes in just jumps around, but never above the actual temperature of the engine. After hooking up to the ECU and seeing it reporting a steady and accurate temperature, I realized that there is a separate single wire temperature sensor for the dash.
While shopping for a replacement I ran across this advertisement:
When not replaced, vehicle may experience inaccurate temperature gauge function, overheating engine, internal engine damage and/or excessive fuel consumption
This would seem to indicate that the data from the single wire temperature sender unit is also used as an input to the ECU, and if this sensor is bad could cause performance problems.
Is this in fact the case, or do these types of temp units just hook straight to the dash without providing input to the ECU?
I've heard wonky coolant temp sensors can cause odd performance problems.
I'm asking both for my specific car and in general.