Does the dash temperature sender unit also provide input to the ECU?

Question

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.

Answer 1

For your 626, I'm seeing two different temp sensors listed. I'm seeing this single bladed one:

Which shows to be associated with the gauge. I also see this two bladed one:

Which I assume is for the ECU. I'm going to give an educated guess and state your Mazda is setup with the separate sensors which works out well in this case.

As for other cars, this is not an uncommon setup. I've seen a lot of different models setup either way. It all depends on how the manufacturer has them setup. I'd suggest it is going to be rarer in newer vehicles. This is because in a lot of them, the ECU runs the dash ... it collects the data from the different components and displays those readouts on the dash. In those cases, you'd only see one temperature sending unit and what you'd see on the ECU if plugged into it gather live data and what is displayed on the dash to be quite similar.