Hi Cynthia, I appreciate you getting in touch. Yes, this alternator is guaranteed to fit the 2003 Mitsubishi Outlander with a 4 Cyl 2.4L engine. Once you receive this new part, use the same box to put the old alternator and ship it back to us. There will be instructions in the package. You can use any courier and make sure to keep the receipt and tracking number. The Warehouse Department will inform the Accounting Department that the core has been received and the core amount will then be released to the same card you used in the order. Use the link below to place your order while the part is in stock. Your order will come with a 30-day post-purchase price match guarantee. I hope this helps and enjoy shopping! https://www.carparts.com/alternator/quality-built/mpa11028?can=CPGG4850_CSQA_20240415