Find and unlock the rear door of an armored patrol car

How do you complete "Find and unlock the rear door of an armored patrol car"?

This is step 4 of 4 in Armored Transports, given by Tianwen. It is completed on The Blue Gate. The exact location is marked on the The Blue Gate map.

• Armored Transports
• The Blue Gate

What are the other objectives in Armored Transports?

Armored Transports has 4 objectives in total: Reach the Checkpoint, Search the Guard huts for an Armored Patrol Key Card, Reach the Traffic Tunnel near the Blue Gate Checkpoint and Find and unlock the rear door of an armored patrol car.