How is exhaust temperature measured?

[particlewave]

I was playing around with the Durametric today, reading some exhaust values, and was curious about how the car measures exhaust temperature. To my knowledge, the car doesn't have an exhaust temperature sensor...

Any insight?

[steved0x]

I wonder if it is from the O2 sensors, can they do it?

[boxfix]

interesting.....there are no sensors in the system.

[The Radium King]

is it exhaust temp, or o2 sensor temp? o2 sensors have a heater in them in order to bring sensors to temp to work properly.

[particlewave]

It's shown in the shop manuals and Durametric as exhaust temp. I monitored it, the o2 readings and o2 heater resistance. I assumed it would be a change in resistance at the heater (like a thermocouple), but the resistance held steady as the temperature rose.

However, testing a spare o2 sensor on the bench while I heated it to 600f degrees with a torch, the heater resistance did change from 3 ohms cold to about 20 ohms hot.
That must be it. I'm not sure why the Durametric shows resistance holding steady.
I guess I'll try heating the sensor on the bench with its own heater and measure the resistance.