Hello
My rear doors wont lock or unlock with the remote,front key, or dash button. I found some diagnostics on the web but Im stuck at the first step..please see below

Ensure doors and trunk are open. Lock unit should be latched
in lock position by pressing in central locking unit latch with a
screwdriver. After fault tracing, release latch by opening door with
inside or outside handle.
CENTRAL LOCKING INOPERABLE
NOTE: Use illustration for central locking relay base terminal
identification. See Fig. 1. etc...

Where is the central locking relay located? Perhaps if I could see it then the central locking unit latch would also make sense to me. Thanks for any info and for putting up with my ignorance