The Check Engine Light came on in my 94 E320 recently. Using the built-in
Diagnostic Trouble Code interface, I found Code 20, which is Speed Signal
I hooked up a code retriver to Pin 14, Cruise Control/Electronic Actuator,
and I got a code 5, Brake Stop Switch. I replaced the brake switch, but the
CEL returned. Still Code 20, but this time Pin 14 gave Code 9, Hall Effect
Sensor. Someone on another board suggested that I need to replace the Hall
Effect Sensor, but that is located within the Instrument Cluster. I rather
not replace the whole cluster, unless I could get a used one inexpensively.
Anyway, how do I know this will fix the problem?
One further piece of information: The wiring harness is fairly new, so I
don't think that is the problem.