I went through a similar episode of encountering every engine error code possible. Turned out to be the engine harness connectors. During a high water situation after heavy rains, some of the connectors were contaminated with water & dirt. On inspection, the dealer found that none of the main harness connectors had any dielectric grease in them. The harness must have been installed "dry". A new harness eliminated all the issues and the good news was my auto insurance covered it under the comprehensive as "storm damage". Since yours is also a 2002, I tend to agree with those posts regarding the status of your electrical connectors.

2002 X5 3.0 273,500 miles
2004 325i 118,000 miles