Hello. Just had this code last month. Replaced the ECU - repaired wiring.
Had to set up with Dealer PC and readjust throttle pot ( Code 24)- Expensive and time consuming - FYI Double and Triple check your Wiring

if there are multiple codes present the display will only display the last (most prominate) code. If you want to see any other codes you will have to go to the pedal dance and get the ecm to display the codes through the MIL or hook up a laptop and run diagnozer and see what other codes are present actively.
The E23 code is probably being detected when key is turned on so it would be prominate first, the spark plug or cam/crank sensor codes would not display until the engine is running or possibly if they would be the only code stored in ecm memory.

I think you are mistaken when you say "displaying e23 code(throttle error)I understand this will not affect starting the engine". I don't think it effects the cranking motor from cranking, but there are codes that will prevent spark and may prevent the fuel lock off from opening too (as well as codes and errors that prevent drive with a running motor). the 'no spark' is the protective measure (preventing a run away motor) as the ECU is recognizing some possible failure to be able to control engine speed, not a 'no spark fault'.