My 2003 impala was diagnosed and it came back with two codes and they are p0742 and p1811.

no,it wont go out until it is reset,fixing those problems will keep it out,but,not for good

P1811
The transmission pressure is modified by an adaptive modifier which controls the shift execution time. This diagnostic tests the time required to accomplish the shift. If the shift takes longer than 0.65 seconds and the adaptive modifier cannot shorten this time, then a counter increases by one.
If the PCM detects a counter value of 2 during one trip, then DTC P1811 sets. DTC P1811 is a type C DTC
The 1-2, 2-3 or 3-4 shift is longer than 0.65 seconds, twice in one trip.
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Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in overdrive.

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Ensure that the current PCM calibration is correct for the final drive ratio.

1. Use the scan tool snapshot mode in order to record the shift times.
2. Drive the vehicle in D4 in order to obtain a 1-2, 2-3 and 3-4 upshift.
3. Record the shift times.

Did all the shift times exceed the specified value?
0.65 seconds
Perform the Line Pressure Check Procedure.
Refer to the Line Pressure Check .
Is the line pressure within specifications?
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Go to Diagnostic Aids
You may want to take this to the dealer !

need to put your car on a scanner to properly diagnose your problems p0440 evap system,128 thermostate ,p0742 torque convertor,p0327 knock sensor. take your car to a good mechanic

Peoples Transmission

i have the same issue in a 2000 chevy impala have the same issue so your tellin me theres so way to acees it without lowering the frame atleast partially ?
and would the transmission control solenoid be the same peice

P0420 catalytic below threshold,Your basically dealing with is a failed catalytic ,
P0742 Torque convertor clutch circuit stuck on or off.
P1811 this is manufacutrer code definition adaptive shift (due to P0742)
P1811 this code is set from towing a trailer in overdrive
when P0742 comes on it usually is accompanied by P1887
If its p1811 then yes it truly is a TCC solenoid being a problem As for catalytic code te catalytic is a mechanical device and yes they do expire from mileage and age

P0742 - Torque converter clutch solenoid circuit stuck on
P1573 - Connection lost between ABS Module and PCM
P1811 - code P1811 will set if a shift into any gear other than reverse and forward engagements takes longer than 0.65 seconds to complete

CODE PO218 - TRANSMISSION FLUID OVER TEMPERATURE.TRANSMISSION FLUID IS LOW OR CONTAMINATED BURNT OR DIRTY.CHECK TRANSMISSION COOLER LINES FOR DAMAGE OR RESTRICTION. CODE PO742 - TORQUE CONVERTER CLUTCH CIRCUIT STUCK ON. CODE P1811 - MAXIMUM ADAPTIVE LONG TERM SHIFT. CODE U1301 - CLASS 2 CIRCUIT SHORT TO BATTERY.POSSIBLE CAUSE CLASS 2 SERIAL DATA LINE WAS IN A HIGH STATE FOR 3 SECONDS DUE TO A SHORT TO VREF OR SYSTEM POWER. ONE OR MORE MODULES ON CLASS 2 LINE HAS AN SHORT TO POWER.LOOKING AT ONE OF THE CODES.TRANSMISSION GETTING TOO HOT.DUE TO OVERHEATING ENGINE OR YOU ARE TOWING OR PULLING MORE WEIGHT THAN YOUR VECHICLE CAN HANDLE.CAUSING ENGINE AND TRANSMISSION TO OVERHEAT.

1.)heated seat is usually the heating elements under the seat cover.
2.)shifting is likely a pc solenoid and valve body.CODE associated with this is a p1811.If your vehicle has high miles or there is alot of debris in the pan of the trans,then I would suggest a reman trans.

P0742: Torque Converter Clutch Circuit Stuck On (transmission area)

P1811: Maximum Adapt and Long Shift 2.4L and 3.1L (transmission area)

You need to talk to a transmission specialist.