What should I do if the 5100 error persists after trying all DIY troubleshooting steps, and what are the potential costs of professional repair?

If the 5100 error persists despite thorough DIY troubleshooting, it likely indicates a more serious internal component failure, such as a faulty carriage motor, main board, or a deeply damaged print head (or cartridges). At this point, it's advisable to contact Canon customer support or take the printer to a certified service center. The cost of professional repair can vary significantly depending on the faulty part and labor rates. For an older, entry-level printer like the MP237, the repair cost might sometimes approach or even exceed the cost of a new printer, making replacement a more economical option.