I have no letter display with codes what does this mean

Question

Which prefix do i use if one not displayed

Answer 1

Depends on what you access, if it s the engine management you use the P codes, If you acess the body codes you will get B codes,  You obviously have P codes P0128 is thermostat rationality,P0403 EGR solenoid circuit, P0406 EGR position sensor circuit high, P2181 cooling system performance, There is no C0,they all start out C1,there is no B0, it also starts out B1.