this started monday night after comming home. and car threw a check engine light which is a code 12 . code 12 is a tach rpm signal, or ecu fault

ok on the way to work car ran great after resetting the ecu, better than it had before but still had code 12. after i got to work, i unhooked the battery cable left if off till i got off 8 hours later. on the way home my car starts randomly missing, the lights both inside and outside are randomly getting bright and dim,and the speedo is going crazy, its jumping 5-10mph up and down from where it should be.

any ideas?
this is on a 94 7afe

well turns out the battery was shot, it had swollen , and the dizzy had gone bad as well, replced both, car runs good now