I am having some problems implementing Google Tag Manager on my website. I have a Google code, and when I try it on my site, it makes a lot of javascript co
Simo Ahava on the Google Tag Manager forums answered this type of question:
Why jQuery might not be defined
Basically, he says that GTM does not load jQuery by default.
Even if your page does load it, the GTM tag that uses it might get triggered prior to the on page loading of jQuery.
You can either make your jQuery code wait for the library to be loaded or load it within the custom HTML tag.