I have an 06 cadillac dts it said check the tpms I get it set to where it's ready to relearn I do the lf tire it takes forever then the horn beeps twice and relearn goes back to service tpms

Just drive it. Sometimes it just takes a little time for the system to update

Does the vehicle have TPMS - tire pressure monitoring system ? Who ever did the job didn't relearn TPMS sensor positions . Take it back .

There are two different ways to relearn your Tire Pressure Monitoring System (TPMS). One is with a TPMS scan tool (this is the preferred method) and the other is the manual method (pain in the "you-know what", but requires no special tools or equipment).

To use the manual method, set the parking brake. Enter into TPMS RELEARN using the Driver Information Center (DIC) controls. (SEE Owner's Manual)

When you have successfully entered TPMS RELEARN, the horn will chirp and the left front turn signal will illuminate. Increase or decrease the tire inflation pressure on the left front tire for 8 to 10 seconds. The horn will "chirp", indicating that the left front tire pressure sensor has been relearned and the turn signal at the right front will illuminate. Repeat the process for the right front tire. The horn will chirp and the right rear turn signal will illuminate indicating that the right front tire has been relearned and now you must now repeat the process at the right rear tire. Then you will have to repeat this a fourth time at the left rear. When the left rear tire has been relearned, the horn will sound a "double chirp" indicating that the relearn process has successfully completed.
At this time, turn the ignition switch to the OFF position and adjust all of the tire pressures to the specification printed on the tire certification label inside the drivers door/door pillar area.

There is a Technical Service Bulletin (TSB) for your vehicle stating that if the light is blinking and if there are dashes (- -) on only one or two tire pressure readings, then the tire presure monitoring system should be put through a "Relearn" or "matching" process. Then if any of the tire pressure sensors do not respond while relearning, the sensor in that tire should be replaced.

The TPMS matching process is outlined below:

1. Set the parking brake.
2. Turn the ignition switch to ON/RUN with the engine off.
3. Go to the TPM vehicle information screen on the DIC. Press set to relearn the sensors. The horn sounds twice to signal the receiver is in relearn mode and Tire Learning Active message displays on the Driver Information Center screen.
4. Start with the driver side front tire.
5. Remove the valve cap from the valve stem. Activate the TPMS sensor by increasing or decreasing the tire's air pressure for 10 seconds, or until a horn chirp sounds. The horn chirp, which can take up to 30 seconds to sound, confirms that the TPMS sensor identification code has been matched to this tire position.
6. Proceed to the passenger side front tire, and repeat the procedure in Step 5.
7. Proceed to the passenger side rear tire, and repeat the procedure in Step 5.
8. Proceed to the driver side rear tire, and repeat the procedure in Step 5.
9. After hearing the confirming horn chirp, for the driver side rear tire, the horn sounds two more times to signal the tire learning mode is no longer active. Turn the ignition switch to LOCK/OFF.
10. Set all four tires to the recommended air pressure level as indicated on the tire and loading information label.
11. Put the valve caps back on the valve stems.
The tires air pressure will not appear on the screen until you start driving the vehicle.

If its reading low and the tire pressure is correct there is a problem with that sensor. Typically they need to be replaced in order to correct the problem. A TPMS tool capable of displaying TPMS sensor data would confirm the bad reading.

They display the tire pressure as a convenience. They don't have to display the pressures and many makes/models do not.

The level of sophistication with these systems is slowly improving. Many newer models will automatically know where the tire is and display it correctly. Unfortunately yours need to be relearned manually after every tire rotation which is very common with earlier systems. It is assumed that this is done after every tire rotation which would then make the displayed tire locations correct.

If you are confident that the correct tire location is being displayed than I wouldn't see any issue with replacing that sensor. If you are not confident the correct tire location is being displayed than it wouldn't be a bad idea to do a relearn procedure.

The TPMS matching process is outlined below:
1. Set the parking brake.
2. Turn the ignition switch to ON/RUN with the
engine off.
3. Press and hold the Remote Keyless Entry (RKE)
transmitter's LOCK and UNLOCK buttons, at the
same time, for about five seconds to start the TPMS
learn mode. The horn sounds twice indicating the
TPMS receiver is ready and in learn mode.
4. Start with the driver side front tire. The driver side
front turn signal also comes on to indicate that
corner's sensor is ready to be learned.
5. Remove the valve cap from the tire's valve
stem. Activate the TPMS sensor by increasing
or decreasing the tire's air pressure for about
eight seconds. The horn chirp, can take up to
30 seconds to sound. It chirps one time and then
all the turn signals flash one time to confirm the
sensor identification code has been matched to
the tire/wheel position.
6. The passenger side front turn signal comes on to
indicate that corner sensor is ready to be learned.
Proceed to the passenger side front tire and
repeat the procedure in Step 5.
7. The passenger side rear turn signal comes on to
indicate that corner sensor is ready to be learned.
Proceed to the passenger side rear tire and
repeat the procedure in Step 5.
8. The driver side rear turn signal comes on to
indicate that corner sensor is ready to be learned.
Proceed to the driver side rear tire, and repeat
the procedure in Step 5.
9. After hearing the single horn chirp for the driver
side rear tire, two additional horn chirps sound
to indicate the tire learning process is done.
Turn the ignition switch to LOCK/OFF.
If no tires are learned after entering the TPMS learn
mode, or if communication with the receiver stops, or
if the time limit has expired, turn the ignition switch to
LOCK/OFF and start over beginning with Step 2.
10. Set all four tires to the recommended air pressure
level as indicated on the Tire and Loading
Information label.
11. Put the valve caps back on the valve stems.

This info can also be found on page 5-66 of your owners manual.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The TPMS light (Tire Pressure Monitoring System) for that vehicle should function as follows.

If the light is on and steady, it means that the pressure in one or more of the tires is too low, and if the light is flashing, then it indicates that one or more of the tires are over-inflated.

1. Turn the ignition key to the "On" or "Run" position but do not start the vehicle. (If the vehicle has an electronic keyless ignition then place the ignition switch in the "ACCY" position)

2. Press the "Lock" and "Unlock" buttons at the same time on the vehicles remote key fob, and keep holding the two buttons down until you hear the horn beep, and usually this takes around five seconds. The horn beep will indicate that the learn cycle has begun.

3. Re-learn the TPMS system. Deflate or inflate air into the driver-side front tire for approximately 8 to 10 seconds and then listen for the horn to beep one time. (the horn might beep before the 8 to 10 second re-learn, or it could even take as long as 30 seconds after)

4. Repeat steps 2 and 3 for the remaining three tires. Also, the remaining three tires must be checked in the exact following order, the passenger-side front tire, the passenger-side rear tire and finally the driver-side rear tire. After the final TPMS sensor has re-learned then the horn will beep twice.

5. Listen for the horn to beep twice. When the horn does beep twice, it wikll be the indicator that the TPMS system has re-learned and reset.

6. Turn the ignition switch to the "Off" position, and then be certain that all four tires have the correct tire pressure as recommended on the drivers door, and the next time that the ignition is turned on, the tire pressure light should be reset.

Let me know if you require any further assistance.

First check for low tire pressures using the Information button (low pressure warning occurs below approx. 26psi). If pressures seem OK, then one of the wheel tpms sensors has probably quit - you can check for error codes (DTCs) using a code reader to see if this is the case, and the faulty sensor will have to be replaced.

try another sensor. it may be faulty.

You have two minutes to match the first tire/wheel position, and five minutes overall to match all four tire/wheel positions. If it takes longer than two minutes, to match the first tire and wheel, or more than five minutes to match all four tire and wheel positions the matching process stops and you need to start over.
The TPMS sensor matching process is outlined below:

1. Set the parking brake.
2. Turn the ignition switch to ON/RUN with the engine off.
3. Press the Remote Keyless Entry (RKE) transmitter's lock and unlock buttons at the same time for approximately five seconds. The horn sounds twice to signal the receiver is in relearn mode and TIRE LEARNING ACTIVE message displays on the DIC screen.
4. Start with the driver side front tire.
5. Remove the valve cap from the valve cap stem. Activate the TPMS sensor by increasing or decreasing the tire's air pressure for five seconds, or until a horn chirp sounds. The horn chirp, which may take up to 30 seconds to sound, confirms that the sensor identification code has been matched to this tire and wheel position.
6. Proceed to the passenger side front tire, and repeat the procedure in Step 5.
7. Proceed to the passenger side rear tire, and repeat the procedure in Step 5.
8. Proceed to the driver side rear tire, and repeat the procedure in Step 5. The horn sounds two times to indicate the sensor identification code has been matched to the driver side rear tire, and the TPMS sensor matching process is no longer active. The TIRE LEARNING ACTIVE message on the DIC display screen goes off.
9. Turn the ignition switch to LOCK/OFF.
10. Set all four tires to the recommended air pressure level as indicated on the Tire and Loading Information label.
11. Put the valve caps back on the valve stems.

TPMS Sensor Matching Procedure

Each TPMS sensor has a unique identification code. Any time you rotate your vehicle's tires or replace one or more of the TPMS sensors, the identification codes will need to be matched to the new tire/wheel position. The sensors are matched to the tire/wheel positions in the following order: driver side front tire, passenger side front tire, passenger side rear tire, and driver side rear tire using a TPMS diagnostic tool. See your dealer/retailer for service.

The TPMS sensors can also be matched to each tire/wheel position by increasing or decreasing the tire's air pressure. If increasing the tire's air pressure, do not exceed the maximum inflation pressure indicated on the tire's sidewall.

To decrease air-pressure out of a tire you can use the pointed end of the valve cap, a pencil-style air pressure gage, or a key.

You have two minutes to match the first tire/wheel position, and five minutes overall to match all four tire/wheel positions. If it takes longer than two minutes, to match the first tire and wheel, or more than five minutes to match all four tire and wheel positions the matching process stops and you need to start over.

The TPMS sensor matching process is outlined below:

1. Set the parking brake.
2. Turn the ignition switch to ON/RUN with the engine off.
3. Press the Remote Keyless Entry (RKE) transmitter's LOCK and UNLOCK buttons at the same time for approximately five seconds. The horn sounds twice to signal the receiver is in relearn mode and TIRE LEARNING ACTIVE message displays on the DIC screen.
4. Start with the driver side front tire.
5. Remove the valve cap from the valve cap stem. Activate the TPMS sensor by increasing or decreasing the tire's air pressure for five seconds, or until a horn chirp sounds. The horn chirp, which may take up to 30 seconds to sound, confirms that the sensor identification code has been matched to this tire and wheel position.
6. Proceed to the passenger side front tire, and repeat the procedure in Step 5.
7. Proceed to the passenger side rear tire, and repeat the procedure in Step 5.
8. Proceed to the driver side rear tire, and repeat the procedure in Step 5. The horn sounds two times to indicate the sensor identification code has been matched to the driver side rear tire, and the TPMS sensor matching process is no longer active. The TIRE LEARNING ACTIVE message on the DIC display screen goes off.
9. Turn the ignition switch to LOCK/OFF.
10. Set all four tires to the recommended air pressure level as indicated on the Tire and Loading Information label.
11. Put the valve caps back on the valve stems.