Here's how to find it:
1. Consult a Repair Manual: The best and most reliable way is to get a repair manual specific to your 1997 GMC Sierra 1500 4WD automatic. This manual will have diagrams showing the exact location and often includes pictures. Chilton and Haynes are popular brands.
2. Transmission-Mounted Possibilities: The VSS is most commonly found in one of these locations on the transmission:
* On the side of the transmission: Look for a sensor that's mounted to the side of the transmission case, often near the top or middle. It might have a single wire or a couple of wires connected to it.
* On the tailhousing (rear) of the transmission: This is another common location. You might need to get under the truck to see it clearly.
* Integrated into the transmission: In some cases, the sensor is integrated into the transmission and not easily accessible without removing the transmission. This is less common, but possible.
3. Look for a Sensor with a Single or Dual Connector: The VSS typically has a single connector (one wire) or a dual connector (two wires). It's a relatively small sensor, often cylindrical or rectangular in shape.
4. Follow the Wiring: If you're having trouble locating the sensor directly, you can try tracing the wiring harness from the transmission back to the vehicle's computer (PCM). This might lead you to the sensor. Be careful when handling wires; don't pull them too hard.
5. Use a Diagnostic Scanner: A professional-grade OBD-II scanner can sometimes pinpoint sensor issues and may provide clues as to the sensor's location.
Safety Precautions:
* Disconnect the negative battery terminal before starting any work near electrical components.
* Use jack stands if you're working under the vehicle. Never rely solely on a jack.
* Wear safety glasses to protect your eyes from debris.
* Be mindful of hot components if the engine has been running recently.
If you can't find it after checking these locations, it's best to consult a mechanic or use a repair manual for your specific transmission type to ensure accurate identification and replacement. Remember that incorrectly identifying or replacing the VSS can cause further issues.
