The generic electronic module (GEM) is equipped on four-wheel drive (control trac system) or two-wheel drive vehicles with power windows. The central timer module (CTM) is equipped only on the two-wheel drive vehicles without power windows. Note: GEM/CTM diagnostics are compatible with New Generation STAR (NGS) Tester.2007-08-22
What is the ECM on a Ford f150?
It is the central computer that controls everything, which includes the charging system, transmission, various emission controls, and communications. Signs of PCM failure may include engine light turning on, truck not starting, engine stalling while driving, or poor engine performance.