When measuring steering wheel play, when should the engine be running?

When measuring steering wheel play, it is essential to have the engine running to ensure that all components of the steering system are properly engaged and functioning as they would during normal driving conditions. Running the engine allows the power steering system to assist in steering, which can provide a more accurate representation of the play and responsiveness of the steering wheel. This is particularly important because, without the engine running, the power steering pump does not operate, potentially leading to readings that do not reflect how the vehicle performs while in motion. Therefore, measuring with the engine on gives a clearer indication of any issues, ensuring a thorough assessment of the steering system's condition.