Check engine light is on something about the TAC?

swap the spark plug over to another spark plug port and check it again if its moved over to the the port you put the other plug then its the spark plug if not then its either the coil or the lead, swap over the coil pack, if you have a multimeter you can do all the checking on kohms settings to check the spark plug . it can be more likely to be the coil pack as they do fail.

The check engine light is telling the driver the computer has a problem with something that can affect performance or emissions.
The problem is serious when the light is flashing.
You would need to have the computer scanned for trouble codes to proceed.

bad wire?bad coil?

The check engine light being on now is a different problem , Have DTC'S - diagnostic trouble codes checked ,will have something to do with electronic throttle control . That is what reduced engine power is about . It's in a reduced power mode.
Reduced Engine Power Mode
When the ECM detects a condition with the TAC system, the ECM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
• Acceleration limiting--The ECM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
• Limited throttle mode--The ECM will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
• Throttle default mode--The ECM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode--The ECM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned off.
- Ignore the accelerator pedal input.
• Engine shutdown mode--The ECM will disable fuel and de-energize the throttle actuator.

Do you know what electronic throttle control is ?
--------------------------------------------------------------------------------
Throttle Actuator Control (TAC) System Description

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system includes the following components:
• The accelerator pedal position (APP) sensors
• The throttle body assembly
• The engine control module (ECM)

Your best bet , take it to a qualified repair shop .

all the codes point to throttle body. clean throttle body, especially around throttle plate. check for loose wires, if problems persist. replace throttle body. p2104 is tac system forced idle, p2111 is tac system stuck open, p2112 is tac system stuck closed. clean throttle body good, and see if this fixes it. then go from there. have a good day !!

did you just replace the plugs or replace ignition wires, rotor, and cap (or) ignition coils if applicable? and you check whether its fuel or spark problem by running the engine and taking the plug wire off the spark plug and seeing if there is spark and noting any change in the engine, if the engine runs rough(er) or stalls then you know there is no problem spark related with that cylender, if no change occours when you take the plug wire off the plug then you know there is either a no spark condition (you will be able to see if this is the case) or if there is spark and it is a fuel problem. self explanatory, if everything you test for passes then you probably have internal engine damage. recommended that you use rubber grip pliers when you take the plug wires off while the engine is running, do not ground yourself. Hope this helps! Joseph.

This is usually caused by a spark plug not sparking. It could be a spark plug, a spark plug wire, or low compression on 1 cylinder. Your check engine light should be on. You can take it to Autozone and have them put it on their scanner and the diagnostic printout will tell you where the mis-fire is at. You can also usually see spark at night time with the hood open in the dark, if it is a spark plug wire.

check air filter and spark plug wires

Have you changed the fuel filter recently?

When the check engine light flashes this is a class a misfire. If this is a 1999 you have a spark plug or a spark plug wire bad. Get a tune up done and replace plug wires.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/terry_db4da071b7da3ac1