This rather depends upon what Country you are in and under what licensing regime.
By a PPL checkride, do you mean a licensing Skill Test for initial issue or do you mean that you have a PPL and have to do a "checkride" for some other purpose i.e. revalidation?
Under the JAA system you can be required to demonstrate use of any equipment fitted to the aeroplane used for the test. You should know what it does and how to obtain basic information from it. You would not be allowed to use it on an initial VFR Navigation leg. Remember the examiner has the right to simulate the failure of any equipment so you must not rely on it.