The license plate 2ABM543 shows up on two different vehicles in this episode. It's on Chen's undercover car and is on the van that Nolan and Juarez pull over after they stakeout Pico Drug. It was also on the car that was involved in the opening traffic stop in the previous episode. It's also used on S5E16 on Vince's pickup truck.
Dr Mitchelssen's car has the license plate 3JRQ158. In S5E21, the same plate shows up twice; first on Lucy's blue UC car, then on a silver Accord where Smitty and Thorsen find the dead liquor store robber in the trunk. It also shows up in The Rookie: Feds S1E3, on the FBI surveillance van.
When Nolan and Juarez are staking out Pico Drugs, they're parked behind a car with the license plate 3Q49927. After arresting Caputo, when Nolan is telling Juarez about Mitchelssen being poisoned, the same plate can be seen on a different car behind him. This plate was also used in S5E4 on Rosalind's blue station wagon, and on S5E3 on Lopez' tail vehicle.