Set up Adwords referrer in Google Tag Manager

Question

I want to track AdWords traffic from Google to siteA.com to siteB.com to the Payment Success page on siteB.com.

I've set up a Google Tag Manager, added Universal Google Analytics with "allowLinker" set to true, allowing me to track traffic from siteA.com to siteB.com, and I've added ecom tracking on the success page (product name, amount, etc).

My client has set up Adwords campaign to send users to siteA.com. I've set up Google Ads Conversion Tracking in Google Tag Manager to fire on the Payment Success page.

This part works fantastically. We can see traffic coming from siteA.com to siteB.com, making a purchase and the ecom values populating in the "Conversions" => "E-Commerce" => "Transactions" page. However when coming from an Adwords link, in Google Analytics, we can see the transactions but all the referrers are "(direct) / (none)".

How do I configure Google Tag Manager to track the referrer as google / cpc on the ecom transaction on the Payment Success page if the referrer was from an Adwords?

Answer 1

both sites need to be using the same GA Property for tracking,
aside from allowLinker set to true in Fields to set,
in More Settings > Cross Domain Tracking In the Auto Link Domains field, enter a comma-separated list of the domains.

Ref: https://support.google.com/tagmanager/answer/6164469?hl=en