Confused - Agreement of past participle in 9.2

Hello

In lesson 9.2 regarding filling your car, there is the statement "l'ha controllata recentemente' 

Howard states that it is 'controllata' not 'controllato' because it refers to Le gomme.  I'm confused by this because my understanding is that the past participle only agrees with the subject in gender and number if it takes the auxiliary verb 'essere'.  But this verb takes 'avere'.

Am I missing something?
Thanks
Anjela

Hi Anjela,

Controllata refers here to la pressione, which is a feminine noun. If you wanted to say "I have checked them", with "them" meaning the tires, you would say Le ho controllate.

The trick here is the pronoun la that replaces la pressione. When a pronoun is present, the past participle agrees with the replaced noun/direct object in gender and number. Thus you will have, for example:

Hai visto Stefano? (Male)
Have you seen Stefano?
L'hai visto? (Lo hai visto?)
Have you seen him?

Hai visto Tiziana? (Female noun)
Have you seen Tiziana?
L'hai vista? (La hai vista)
Have you seen her?

Ho letto tutti i libri.
I (have) read all the books.
Li ho letti tutti.
I (have) read them all.

Ho riordinato le cartelle.
I (have) reorganized the folders.
Le ho riordinate.
I (have) reorganized them.

Hope this helps!

Lucia