Electronic Spark Timing (EST) bypass circuit or EST circuit is grounded or open. HEI Module may be the cause
replace the ignition module Its under the rotor inside the distributer cap
Repair kit availale at most auto parts stores
coil, wire, ignition control module
I have a 92 s10 blazer and my code 43 was fixed by replacing the knock sensor. so maybe check the knock sensor and the wiring from that to the ECM.
Code 43 = Electeroic Spark Timing (EST) circuit low voltage detected OR ESC circuit problems. Without being there to put a meter on different components and check it out, all I can do is point you to the electronic spark control module.
You will need to remove the dashboard panel in order to replace the electronic throttle control light. With the dashboard panel removed the light can be access to be replaced.
I would replace the ignition control module that's in the distributor.
Electronic Spark Control Code 43 Speed density 1990-92 Hope this helps, jr Yo go to chevythunder.com dude, you'll find more than you'll ever need
You replace it you do not fix it.
Replace the ignition module. It under the rotor under the distributer cap Held on by two 5.5 mm head bolds and make sure you use new di-electric grease or the new one will burn out FAST
You need to have the system checked for codes. You can then diagnose and find and repair the cause.