check engine ligt on my wifes camry

jo7mge

ENIGMA
Jul 19, 2007
52
0
0
34
Anaheim
my wife got a 1990 toyota camrey with the 2vz-fe V6 engine non-all-trac model and its giveing me codes
12-R.P.M. signal
42-Vehicle speed signal
71-Exhaust gas recirculation sensor signal

i want to fix it myself but dont know where to start any ideas on what can be letting these signals go off?