Unfortunately you must have a scanner to deal with your problem. With 96 or newer cars all info is digital and there is prescribed self-diagnostics in all cars.
There is a company called EASE that makes a PC based tool that can read codes, give actual values, give freeze frame info and give monitor status. For more about this and the software see;
As the page states you can do this about as well as any of us for about $300. They even make a device for monitoring your children who drive. It attaches to the OBDII port and gives such vitals as top speed, top RPM, top load, miles driven and others.
ONE point to understand; this is a very capable tool for engine management systems ONLY. It will do nothing else, but it will allow monitoring while driving (BE REAL CAREFULL -- USE A SECOND PERSON)all the vitals.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician