I have run in to this problem to. The roll pin connecting the pedal to the sensor breaks allow the adjustments to change. It drove me crazy till I found it. make sure pedal stop, under pedal is adjusted. This fixed my issue completely!! Hope this helps!!

cat has a service bulletin out on this code
it is related to what edward talks about with the pedal stop screws and also checking the pedal position sensor voltages

first i would check the pedal linkage and make sure the stop screws have not been tampered with, make sure they are not loose or broken.

then you can do the released pedal released learn by doing the following:
1) Turn key switch to the ON position and count out 2 seconds.
2) Turn the key switch OFF and count out 10 to 12 seconds.
3) Turn the key switch ON and count out 2 seconds.
4) This learn is completed. You may key off now.

then of course if the code is still present you will have to check the voltages on the pedal sensor:
key on (engine stopped)pedal fully depressed:
sensor1: 4.2v (terminal 106)
sensor2: 2v (terminal 98)

key on (engine stopped) pedal fully released
sensor1: 0.6v (terminal 106)
sensor2: 0.3v (terminal 98)

if you verify that the pedal sensor is out of range, replace the sensor, set the voltages to the above settings and the code should go away. If it does not go away then do the pedal dance as edward described and clear the code.
If the code is still persistant then you have bigger problems and will need to do more extensive troubleshooting to locate the source of the issue.

good luck

and make sure no one screwed the pedal stop screw down trying to make their truck faster. error can be set when the linkage extends past expected parameters.
bear of the problem is,,,
being this is a pedal related code, you can not clear the code with the pedal dance.
you may wind up getting the dealer's tech to clear this one.

Code E-24 is for the Accelerator pedal position sensor,malfunction. These trucks are a drive by wire with no cable that goes to the engine,I would replace the Accel pedal sensor.