Which relay controls the transmission on a 2002 Chrysler town and country?

There isn't a single relay dedicated solely to controlling the entire transmission in a 2002 Chrysler Town & Country. The transmission's operation is managed by a complex system involving the Powertrain Control Module (PCM), various sensors, and several relays that control specific components *within* the transmission system (like the transmission shift solenoids). There's no one relay you can point to and say "that's the transmission relay."

To diagnose transmission-related problems, you'd need to consult a wiring diagram specific to your vehicle's year and transmission type (e.g., 3-speed automatic, 4-speed automatic). These diagrams show which relays are involved in the transmission's electrical circuits and their functions. A malfunctioning relay might cause transmission problems, but pinpointing the specific relay requires a deeper diagnostic process than simply naming one. You'll likely need a professional scan tool to check for diagnostic trouble codes (DTCs) from the PCM to identify the root cause.