Got this code from a survey they sent me. Sharing as it appears to be generic. Worked for me as an existing user but YMMV. If you are a new user make sure to use a referral code below to get an extra 3 free unlocks.
To redeem the code, open the Lime app, select ‘Wallet’ and then ‘Add a Promo Code’, and enter and apply code. The code is valid for 1 free unlock on each of your next 3 rides.
You must apply the code to your account before 29 February, 2020 at 11:59 PST. Discount is valid from when you apply the code to your account until it expires on 31 March, 2020 at 11:59 PST.
Code valid in Australia only.
Quantities are limited and applied on a first-come-first-served basis. Limit one redemption per person.