Try and determine the make of decoder.
Reading CV8 will tell you the Manufacturer ID.
Then reset the decoder accordingly.
Lenz : CV8 should be 99. To reset, enter a value of 33 in CV8.
Hornby: To reset the R8215 Decoder, enter a value of 8 in CV8.
NCE: CV8 should be 11. To reset, enter a value of 2 in CV30.
Bachmann: CV8 should be 101. To reset, enter a value of 33 in CV8.
TCS: CV8 should be 153. To reset, enter a value of 2 in CV8.
Then power off and then on again.
Table of Manufactuer IDs at the NMRA.
Reading CV8 will tell you the Manufacturer ID.
Then reset the decoder accordingly.
Lenz : CV8 should be 99. To reset, enter a value of 33 in CV8.
Hornby: To reset the R8215 Decoder, enter a value of 8 in CV8.
NCE: CV8 should be 11. To reset, enter a value of 2 in CV30.
Bachmann: CV8 should be 101. To reset, enter a value of 33 in CV8.
TCS: CV8 should be 153. To reset, enter a value of 2 in CV8.
Then power off and then on again.
Table of Manufactuer IDs at the NMRA.