The cost of knock sensor replacement is difficult to calculate. The hourly fee of a mechanic varies depending on the vehicle, problem, and location. Typically, the mechanic will diagnose the situation after visiting a garage to be confident about the fix. In most circumstances, the diagnosis time is billed hourly. The hourly rate is between $75 to $150. Depending on the nature of the problem, the diagnosis could take an hour or two hours. A knock sensor can cost between $10 and $100, with replacement costs ranging from $180 to $300. Depending on the mechanic, the entire procedure will cost between $500 and $700. The price is not set in stone and will vary depending on where you go. So, be sure to remember the prices along with their distances!