ok i currently have two disco's, one 2001SE which my wife drives and one 2003 which i drive. on the 2001SE i have noticed the tach just took a crap and stopped working and at the same time the downhill decent light illuminated.???thinking maybe alt-tach tire? suggestions appreciated.
Now on the 2003, i have noticed the three amigos, however after i wash it and clean the wheel wells with the pressure washer they go off but tend to come on while in traffic a couple of days later. ?? guessing that the wheel sensors get dirty from brake dust maybe??? once again any suggestions would be much appreiciated

 

Tach drive for D2s does not come from the alternator (it does on D1s). Instead it comes from the CKP sensor via the ECU. You may have a wiring or header problem. Obviously the CKP is still good or you could not start.