See, I'm not really that good at electrical, but I'm thinking they can be tested. Given the age of you're truck and predicted mileage, it's not uncommon. If replacing one, my advice is replace all. Maybe keep the old ones "in case", but if you confirm a coil bad, that's my advice. Ebay has cheap deals, I'd lean more towards a Motorcraft coil personally, number 2 would be motoblues, I guess they are good too.