To be certain, you should:
* Consult your owner's manual: This is the best resource for the precise location in your specific vehicle.
* Look for labels: Some components under the hood will have labels indicating their function.
* Search online: Use a search engine with your specific year and model of GMC Safari (e.g., "2003 GMC Safari ECM location") to find images and forum discussions showing the location.
Be aware that accessing the ECM may require removing other components, so be careful and take pictures before disassembling anything if you plan on working on it yourself.