Look at the hind quarters of the first-generation Jetta, and you might notice that the bottom of the rear window seems oddly low next to the top of the trunk lid. This little styling quirk stuck with the Jetta all the way up to 2005, but it wasn't because the lower window enhanced visibility. No, this misalignment was due entirely to the fact that in order to create the car, VW just replaced the Golf hatchback's rear hatch cover with fixed glass and a protruding cargo box. Leave it to the Germans to turn a tacked-on trunk a trademark styling cue.
In the American market, the 2009 VW Jetta came with three different engines. The base engine was a 170-horsepower, 2.5-liter, inline five-cylinder powerplant; GLI models got a 200-horsepower, turbocharged 2.0-liter, and the newly reborn Jetta TDI got a 140-horsepower, direct-injected four-cylinder diesel. Regardless of the engine, all used a pair of oxygen sensors: one at the exhaust manifold, and a second in the pipe, just after the catalytic converter. If you get an O2 sensor fault code, Sensor 1 is the upstream sensor on the exhaust manifolds, and Sensor 2 is the downstream sensor, after the converter. On 2.0-liter engines, the downstream sensor is screwed directly into the catalytic converter.