2003 Chevy Blazer temp and directional reading

Welcome, are you talking about the gage reading? Did you take an independent engine temp reading, compare to gage reading? Maybe a problem with dash cluster, sending unit, wiring circuit, thermostat?

You said the reading is off 30 degrees, high or low?

If you think the reading is accurate, check the thermostat and coolant flow through the radiator.

Sorry, my bad, I found this wiring info.

Not sure if you can read it. If I magnify it too much, I can't get the whole diagram on the screen. The ambient temp sensor is front center of vehicle, behind fascia. The higher the temp, the lower the resistance reading across the sensor. At 81 degrees the min ohms spec is 11150, max ohms spec is 11250 across sensor. The problem could be the sensor--wiring circuit--or driver information center.