Where is the firewall? My gauges are going crazy and someone told me to check the ground on the firewall. I am clueless. 2007 Town and Country

It's the barrier between the engine compartment and passenger cabin.

There are dozens of ground bonding points located across the vehicle.

The firewall is the metal panel between the engine and the dashboard, from the base of the windscreen to the floor of the car. The ground on the firewall may be the issue as you were told. Loosen and remove the bolt of the ground wire and clean the end and also where it is bolted on, then tighten. Check for any other loose or corroded connections including the battery terminals. Also check for any electrical short in the wire harness.

Hooking up a professional scan tool and checking for DTC'S - diagnostic trouble codes would be the smart first step . Your vehicle has 10 to 20 control modules (computers ) or may be more . They all share information on the CAN bus - controller area network , a serial communication network . power or ground problems and module problems can an will set DTC'S in one module or another . The instrument cluster has a microprocessor inside it an can set DTC'S as well . Plus something else to think about is the TIPM - Totally Integrated Power Module . Suggest you read this an then call the dealer to see if your vehicle falls under the recall . https://tipmrebuilders.com/chrysler-tipms-demystified-how-to-reliably-trace-specific-vehicle-symptoms-to-tipm-failure/

First, follow black wire coming out from battery. It is connected somewhere to chassis. Make sure that connection is clean and tight. Check battery terminala if connection is tight.