1985 caprice help

its a 85 caprice 5.0 engine hi my check engine light came on so i bought a tester for my car and tested it i got error codes 12 and 42.....
.code 12 sais "this code will flash whenever the diagnostic terminal is grounded with the ignition on and the engine not running.. if this code appears while the engine is running, no reference pulses from the distributor are reaching the ecm.."
Code 42..."Electric spark timing" sais "poor electric connection, open or short circuit; defective ignition module; defective ecm.."
please help.....
the light is on while the engine is runnin.....i have no idea what this could be any help will be great thank you....i replaced the ignition coil and distributor my car runs

its a 85 caprice 5.0 engine hi my check engine light came on so i bought a tester for my car and tested it i got error codes 12 and 42.....
.code 12 sais "this code will flash whenever the diagnostic terminal is grounded with the ignition on and the engine not running.. if this code appears while the engine is running, no reference pulses from the distributor are reaching the ecm.."
Code 42..."Electric spark timing" sais "poor electric connection, open or short circuit; defective ignition module; defective ecm.."
please help.....
the light is on while the engine is runnin.....i have no idea what this could be any help will be great thank you....i replaced the ignition coil and distributor my car runs

with the code 12 this is normal ..... key on, engine off ///no tach signal to computer/electronic control unit...

code 42 is electronic spark timing [EST] bypass circuit is grounded...

did you replace the cap/ignition module / rotor ?

so again what did you replace? because this is a little weird when you say you replaced ignition coil and distributor and what about the other componets as this is not a usual way to service this ignition system ...

Code 42 will occur if the EST cable to the distributor is disconnected (the 4 wire connection to the distributor). Make sure this cable is connected. You have to disconnect it in order to replace the distributor.

i replaice all that you said and the light turned off thank you

with the code 12 this is normal ..... key on, engine off ///no tach signal to computer/electronic control unit...

code 42 is electronic spark timing [EST] bypass circuit is grounded...

did you replace the cap/ignition module / rotor ?

so again what did you replace? because this is a little weird when you say you replaced ignition coil and distributor and what about the other componets as this is not a usual way to service this ignition system ...

i replaced the ignition module and the light turned off lol i dont kno y i let that pass me thank you

i replaced the ignition module and the light turned off lol i dont kno y i let that pass me thank you

the ignition modules normally fail around 175,-225,ooomi..but if you had arcing this causes them to fail shortly after this arcing event...

good luck with your vehicle ..