Re: VW Caddy, year 2001, engine code AYQ | Posts 16+

dr.zikzak wrote:

Are there any other ways to definitively identify the relay as the cause or to rule out other potential issues (e.g., broken cable, loose connector, faulty MSG,...)?

At most, in specific cases, because the relay in the socket, along with the connectors and cables, forms a functional unit: if you can trigger the error by manipulating the relay, it could be a hairline crack in the relay itself, or a cable break in the immediate vicinity.

You could drill a small hole in the relay housing through which you can manually actuate the load contact with a tool.
If the motor is not running, you can determine whether the relay has been activated by checking the travel of the actuator. If the relay has been activated, you can rule out the coil circuit and look for the problem in the load circuit (e.g., broken wires, burnt load contacts). If the relay has not been activated, the problem lies in the coil circuit. Cables and MSG switching stage).

...or you can install the relay without the cover and drive with the fuse box open, so you can immediately see if it has engaged.