First, has he been seen by the doctor to rule out a physical reason?
Then, I suggest the consequence needs to be related to the offense. Cleaning it up is a consequence in it's self. No need for an additional consequence. Lectures/talking to him will not help. He already knows what you expect. I suggest trying an compassionate approach suggesting he feels bad about this. That he knows not to pee on the floor. Ask him to help you figure out how to stop it. Most important is to remain calm and respond with a more neutral
voice.
Saying he would have to wear diapers like a baby is also not helpful. You want him to be a big boy. Expect him to learn how to be a big boy. (Here is an experience that I remember when I was 3-4. I accidently wet my panties. Mom told me I'd have to wear a diaper like my baby brother. I can still see where I was, feel my Mom's anger, and how I felt humiliated. I cried and cried.)
I suggest he is needing more attention. Negative attention is better than not enough attention. How much time do you spend with him? Do you know what interests him? How much time do you spend time with him doing fun things?
Do you think he feels loved? Is this a reaction to change and/or stress in his life?
I suggest rewards work better than punishment. If he uses the toilet, you'll get ice cream, go to a movie, watch TV with you. Find out what he likes and make doing it a reword.
When you know or strongly suspect he's lying dom't ask if he's lying. In a matter of fact way, say I don't believe you or sure sounds like lie. If the lie is obvious and you can use humor. Humour distracts from the tense situation. "You really think I didn't see, then put fingers around eyes and in a joking manner say something like "I'm the great seer' I see everything in a dramatic way. Both of you laugh.
Sometimes it helps to just calmly stand with him while saying do you want to watch this show or go play? You can do that when you tell me the truth. This has to be said without anger. Be confident and use very few words. Expect him to eventually tell the truth or enough of the truth that you can add to what he says.
In some situations you can say, "that would be fun nevertheless you must do....."
My granddaughter at five, would tell tall tales. One was that her aunt lives in that house and points to it. Let's go see her. My response would be something like, that would be fun but she doesn't live there. If she continued the fantasy, I would say, you really want to see aunt..... then we could talk about the aunt and why we'd like to see her. She forgets about the house. Similar with "I didn't peel on floor." Your response could be, I wonder if you wish you hadn't peed on the floor.
Taking away somethin that's unrelated to the lie, does not teach him how to tell the truth. It's apt to make him mad instead.
I suggest you read How to Talk So kids Will Listen and How to Listen so Kids Will Talk by Adele Farber.