Some people might not comprehend what an E46 is. Understanding of what a E code is going to be the beginning in understanding the terminology E46. BMW started classifying their versions with the E
identification in 1968 starting with the E3 and E9. The 4-door was the E3 and the coupe was the E9 E designations are issued by the manufacturer for different body style cars. The same style can be made for a handful of different years without actually changing the style of the car.
BMW will design the same car for a few years with small changes. This enables identical parts to fits multiple years this saves costs. Look at the E46 as an example. The E46 started production in 1998 as a 4-door and in 1999 as a 2-door. Production ended in 2005 for the sedan but the M3 and coupes proceeded till 2006. For each BMW 3-series from 1998-2005, 80% of the components are the exact same.
Whereas most of the parts are the same, there are several components that the parts differ like engines and optional equipment. Parts like the suspension or dash as an example are identical throughout each model except for the upgraded suspension on the Sport package and m3 variants. Apart from the sport package or M3, 70% of the 3-series production from 1998-2005 has completely interchangeable suspension. The exact same arms and bushings and the same shocks and struts.
This carries true to accessories like the ac and heater, windows, lighting and similar options. The AC condenser is exactly the same on a 1998 323i as it is on a 2006 M3. And also the hood shocks and belt tensioner. In addition, body components straddle several years, particularly the hood and fenders. These are different in addition to the doors on the 2-doors models. The bumpers are a cosmetic piece that has been updated over time to refresh up the design.
Computer systems and safety parts stay the same through E46's Other than program updates, most computer modules have remained the same in particular units like the ABS module or Air Bag computer. It is also normal for a part to be re-designed mid way through manufacturing and afterwards applied to prior models. This is called superceding.
Superseding components is needed when you have a significant failure rate. A component that was superceded many times is the steering pump. A lot of problems have brought the designers at BMW to revise it just about 12 times. Previous versions were not powerful enough to turn the wheels while the interior components would quickly degrade. Engine cooling parts are perhaps the most often repaired parts. Should you own an E46, it's likely you'll switch a water pump and thermostat housing no less than once. Elements like the radiator and coolant reservoir are composed of an ABS plastic which has had a inclination to get brittle in time.
Plenty of components, like the E46 323i control arms have not been re-engineered. Except for cooling components, the E46 from 1998-2005 is most likely one of the most reliable BMW's. It shows in the sales numbers making the BMW E46 the most successful BMW ever.