Short answer: a modern vehicle has many computers, called modules, that each control one system. They talk to each other over a network. These are the most common:
- ECM / ECU (engine control module)
- Controls fuel, ignition and emissions for the engine.
- PCM (powertrain control module)
- An ECM that also controls the automatic transmission. Common on Ford, GM and Chrysler vehicles.
- TCM (transmission control module)
- Controls shifting on vehicles with a separate transmission computer.
- BCM (body control module)
- Controls interior and exterior lights, power locks, windows, wipers and often anti-theft. Some makes call it a GEM, SJB or TIPM.
- ABS module
- Controls anti-lock braking and often traction and stability control. Usually attached to the brake hydraulic unit.
- Instrument cluster
- The gauges and warning lights. Often stores mileage and anti-theft data.
- Radio and infotainment
- Audio, screen, navigation and phone connection.
- HVAC / climate control module
- Controls heating, air conditioning and fan settings.
- Transfer case module
- Controls 4WD and AWD engagement.
- Keyless entry, door, seat and liftgate modules
- Control individual comfort and convenience features.
Replacing a module
Modules are matched by part number, and many need programming after installation. See How to find your module’s part number and Do I need to program a replacement module?
Find your module
Search the part number from your module’s label on Module Mountain, or shop by vehicle. Every module is refurbished to order, ships free by USPS Priority in the USA, and is covered by our one-year warranty (exchange and warranty policy). Can’t find your number? Email contact@modulemountain.com with a photo of the label and your VIN.