The main computer module in a 2005 Mercury Grand Marquis, the Powertrain Control Module (PCM), is typically located
under the hood, often near the firewall on the passenger side. However, its exact location can vary slightly depending on the specific options and configuration of the vehicle. It's usually a relatively large, rectangular black box with numerous connectors.
It's advisable to consult a repair manual specific to a 2005 Mercury Grand Marquis to pinpoint its exact location with diagrams. You can also often find diagrams online through sites like autozone.com or others offering repair information. Be cautious when working near the engine compartment; ensure the engine is off and cool.
