From the Secrets options, go to the Code Entry Screen and enter the following cheats:

NOTE: These codes need a bonus code which will only work on certain discs. It might be necessary to try more than one.

Bonus Code 76538

Group B Mode and Cars:
RTNITJ

Bonus Code 34674

All Bonus Cars:
ZCNGMW

Expert Mode:
IRZQNT

Mirror Tracks:
FEQRJV

All Tracks:
HCHSFD

Bonus Code ?

All Weather:
CLRWTR

Group B Mode and Cars:
CFCKGL or YFHPGW

All Bonus Cars:
AIDLAU

All Tracks:
BSDJUC

Expert Mode:
HIQNRM

All Parts:
FUDWHC

All Tests:
DMLPOD

Mirror Tracks:
EPDZJF