What is limp mode?
When the ECU (engine control unit) notices a problem with one of the powertrain systems that can cause major damage, it sends the engine into limp mode. Now, when a vehicle is in limp mode, the power is significantly reduced, the vehicle will have a speed limit (20 mph), and sometimes it won’t shift higher than the third gear.
Probably best to identify why the care went into limp mode so let's get the codes
Someone said get the codes by doing the key dance which is
"without actually starting the car, you put the key in the ignition and turn it ON-ACC-ON-ACC-ON and leave it there."
the codes should show up in the odometer.
COMMON Issue is the ETC (Electronic Throttle Control)
Someone said, "Try resetting the ETC (Electronic Throttle Control) which is a plastic switch under the pedal.. To reset the ETC place you vehicle in the run position without starting and depress the gas pedal and release all in 2 seconds (1 down and 1 up). You should hear a confirmation "ding" if done correctly. I'm not sure if this process is the same on all Dodge vehicles but I would bet it is."
Some mentioned changing the pedal assembly for the throttle is pretty easy. "the throttle/pedal assembly is really easy to replace. Remove the 3 nuts, drop it down. There's about 6 inches of wire. Then unplug it.
The pedal I removed was part number 04891585 AC. The new part was 04891585 AD."
Throttle Body Issues
A common issue on the second generation Avenger is a malfunctioning throttle body.
This problem typically only affects Dodge Avengers equipped with 2.4-liter 4-cylinder engine and can occur in all model years from 2008 to 2014.
Common symptoms of a faulty throttle body in the Avenger include:
Lightning bolt symbol on dash for Electronic Throttle Control (ETC) issue
Goes into limp mode and can’t get to higher speed
Engine stalling problems
Rough idle
Check engine light
The throttle body in the Avenger’s 2.4-liter engine can get clogged up with gunk and oil from the PCV (Positive Crankcase Ventilation) system.
When it gets too dirty, the butterfly valve can start to bind and start causing engine running problems.
Over time, the plastic gears that turn the valve can wear out and break due to the binding.
A lot of Avenger owners were able to fix their engine stalling and limp mode issues by cleaning out the throttle body using a fuel system cleaner or something like Sea Foam Spray.
You can also replace the throttle body which costs $200 to $300 at an auto parts store.
After replacing the throttle body, you’ll also need to recalibrate it using these steps:
Turn the ignition to the “ON” position
Wait for most of the dashboard lights to go out
Slowly step on the gas pedal and hold it down for 20 seconds
Slowly release the gas pedal
Switch the ignition to “Off”
In some cases, Avenger owners have also had to replace their ECU to fix their stalling and limp mode problems.