2007 q7 3.6 with the following codes? where to start for tyre/tire preasure all at 42 pst on 18 inch 255's

code 01521 and 01833 once i cleared codes only 01521 now shows... what would you check/do next ????????????


Monday,05,March,2012,20:56:59:57529
VCDS Version: Release 11.11.2

Address 65: Tire Pressure Labels: 4F0-910-273-BA.lbl
Control Module Part Number: 4F0 910 273 B HW: 4F0 907 273 A
Component and/or Version: Reifendruck 3 H05 0100
Software Coding: 0062424
Work Shop Code: WSC 31414 790 00001
VCID: 2241D49FFDD4D03
2 Faults Found:

01521 - Sensor for Tire Pressure
002 - Lower Limit Exceeded - MIL ON
Freeze Frame:
Fault Status: 11100010
Fault Priority: 3
Fault Frequency: 2
Reset counter: 81
Mileage: 146824 km
Time Indication: 0
Date: 2012.03.03
Time: 17:10:21

Freeze Frame:
(no units): 21.0
Voltage: 14.10 V
(no units): 19.0
Not Recogn.
Not Recogn.
Not Recogn.
Not Recogn.

01833 - Antenna for Tire Pressure Monitoring; Rear (R96)
004 - No Signal/Communication - MIL ON
Freeze Frame:
Fault Status: 11100100
Fault Priority: 3
Fault Frequency: 2
Reset counter: 78
Mileage: 146601 km
Time Indication: 0
Date: 2012.03.01
Time: 18:42:31

Freeze Frame:
(no units): 4.0
Voltage: 14.00 V
(no units): 142.0
Not Recogn.
Not Recogn.
Not Recogn.
Not Recogn.

second test
Monday,05,March,2012,21:01:43:57529
VCDS Version: Release 11.11.2

Address 65: Tire Pressure Labels: 4F0-910-273-BA.lbl
Control Module Part Number: 4F0 910 273 B HW: 4F0 907 273 A
Component and/or Version: Reifendruck 3 H05 0100
Software Coding: 0062424
Work Shop Code: WSC 31414 790 00001
VCID: 2241D49FFDD4D03
1 Fault Found:

01521 - Sensor for Tire Pressure
002 - Lower Limit Exceeded - MIL ON
Freeze Frame:
Fault Status: 11100010
Fault Priority: 3
Fault Frequency: 1
Reset counter: 85
Mileage: 147095 km
Time Indication: 0
Date: 2012.03.05
Time: 21:01:31

Freeze Frame:
(no units): 0.0
Voltage: 13.90 V
(no units): 19.0
Not Recogn.
Not Recogn.
Not Recogn.
Not Recogn.
Monday,05,March,2012,21:03:45:57529
VCDS Version: Release 11.11.2