* Engine Coolant Temperature (ECT) Sensor: This is the most common sensor people are interested in. It's usually located on the engine block, near the thermostat housing. It's a relatively small sensor with one or two wires connected. Its exact location will vary slightly depending on the engine (I4, V6, or V8). A visual inspection with a repair manual or online diagrams specific to your engine is best.
* Transmission Fluid Temperature Sensor: This sensor is located in the transmission itself. Access requires removing parts of the transmission. You generally won't need to access this unless there's a transmission-related issue.
* Outside Air Temperature Sensor: This sensor is typically located in the front bumper or grille area, often integrated into another component. It measures the ambient air temperature for the climate control system.
* Other Sensors: There may be other temperature sensors for various systems (like the climate control system) with less accessible locations.
To find the specific sensor you need, you should:
1. Consult a repair manual: A Haynes or Chilton repair manual for your specific 2004 Chevrolet Trailblazer year and engine will have diagrams and instructions showing the location of all sensors.
2. Use an online parts diagram: Websites like AutoZone, Advance Auto Parts, or others offer online parts diagrams. Enter your vehicle information and you can often find diagrams showing the location of the sensors.
3. Search online forums: Search forums dedicated to Chevrolet Trailblazers. Someone may have already posted a picture or description of the sensor location you're looking for.
Without knowing *which* temperature you're interested in, it's impossible to give a precise location. The engine coolant temperature sensor is the most likely candidate if you are experiencing engine-related temperature issues.
