I never give up, they have to drag me away kicking a screaming from the car clutching lap top and multimeter... I am fighting nightmare CAN BUS issues on a 2015 Altea at the moment. This computer aided diagnosis is all well and good but if the modelus won't talk or give nonsensical codes they it's a sketch. I mean, look at this report; half the devices VCDS says are OK don't even communicate and ODIS would have none of it.

Code:
                                     VCDS
           Windows Based VAG/VAS Emulator Running on Windows 7 x86
        VCDS Version: Release 20.4.2    Data version: 20200730 DS317.0
                              www.Ross-Tech.com
                      Dealer/Shop Name: C&R Enterprises
                       Workshop Code: 210 01523 000002
                              Self-Diagnosis Log
                     Friday,21,August,2020,09:39:13:16454
               VIN: VSSZZZ5PZFR******   License Plate: 
              Mileage: 44630km-27731mi   Repair Order: Full scan

    Chassis Type: 5P-SE35 (7N0)

    Scan: 01 03 08 09 10 15 16 17 19 25 2E 37 42 44 46 52 56 61 62 72
            
    VIN: VSSZZZ5PZFR011914   Mileage: 44630km-27731miles

    01-Engine -- Status: Malfunction 0010
    03-ABS Brakes -- Status: Malfunction 0010
    04-Steering Angle -- Status: OK 0000
    08-Auto HVAC -- Status: OK 0000
    09-Cent. Elect. -- Status: OK 0000
    10-Park/Steer Assist -- Status: Malfunction 0010
    15-Airbags -- Status: Malfunction 0010
    16-Steering wheel -- Status: OK 0000
    17-Instruments -- Status: Malfunction 0010
    19-CAN Gateway -- Status: Malfunction 0010
    25-Immobilizer -- Status: OK 0000
    2E-Media Player 3 -- Status: Malfunction 0010
    37-Navigation -- Status: Malfunction 0010
    42-Door Elect, Driver -- Status: OK 0000
    44-Steering Assist -- Status: OK 0000
    46-Central Conv. -- Status: OK 0000
    52-Door Elect, Pass. -- Status: OK 0000
    56-Radio -- Status: OK 0000
    61-Battery Regul. -- Status: OK 0000
    62-Door, Rear Left -- Status: OK 0000
    72-Door, Rear Right -- Status: OK 0000
    ---------------------------------------------------------------------
    Address 01: Engine (J623-CAYC)       Labels:. 03L-906-023-CAY.clb
       Part No SW: 03L 997 558 F    HW: 03L 906 023 KL
       Component: R4 1.6l TDI   H43 9982  
       Revision: --H43---    Serial number:               
       Coding: 00114036032501080000
       Shop #: WSC 00049 770 00126
       ASAM Dataset: EV_ECM16TDI02103L997558F 003003
       ROD: GV_ECM16TDI021PQ36.rod
       VCID: 40CC49CFDBC3858653-8014
    7 Faults Found:
    6056 - No Communications with HVAC Control Module (J301) 
              U0164 00 [047] - -
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 11
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:00:46
                    Engine speed: 0.00 /min
                    Normed load value: 0.0 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 19 °C
                    Intake air temperature: 20 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 14.231 V
                    Unlearning counter according OBD: 40
                    Driver request torque-TQI_DRIV_SUB: 0.00 Nm
                    Control Module temperature-TECU: 27 °C
    6082 - Steering Column Control Module 
              U0212 00 [047] - No Communications
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 11
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:00:46
                    Engine speed: 0.00 /min
                    Normed load value: 0.0 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 19 °C
                    Intake air temperature: 20 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 13.327 V
                    Unlearning counter according OBD: 40
    7318 - Body Control Module (Central Electric) 
              U0140 00 [047] - No Communications
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 1
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:01:43
                    Engine speed: 799.50 /min
                    Normed load value: 28.6 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 20 °C
                    Intake air temperature: 19 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 13.214 V
                    Unlearning counter according OBD: 40
                    Driver request torque-TQI_DRIV_SUB: 0.00 Nm
                    Control Module temperature-TECU: 28 °C
    7319 - Body Control Module (Central Electric) 
              U0140 00 [047] - No Communications
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 1
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:01:40
                    Engine speed: 822.75 /min
                    Normed load value: 30.2 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 19 °C
                    Intake air temperature: 19 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 11.972 V
                    Unlearning counter according OBD: 40
                    Driver request torque-TQI_DRIV_SUB: 0.00 Nm
                    Control Module temperature-TECU: 27 °C
    7455 - Door Control Module - Driver's Door 
              U0199 00 [047] - No Communications
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 2
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:00:46
                    Engine speed: 0.00 /min
                    Normed load value: 0.0 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 19 °C
                    Intake air temperature: 20 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 14.231 V
                    Unlearning counter according OBD: 40
                    Driver request torque-TQI_DRIV_SUB: 0.00 Nm
                    Control Module temperature-TECU: 27 °C
    11831 - Function Restricted due to Missing Message(s) 
              U1111 00 [047] - -
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 2
                    Mileage: 44613 km
                    Date: 2020.08.20
                    Time: 00:00:46
                    Engine speed: 0.00 /min
                    Normed load value: 0.0 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 19 °C
                    Intake air temperature: 20 °C
                    Ambient air pressure: 990 mbar
                    Voltage terminal 30: 14.231 V
                    Unlearning counter according OBD: 40
    10457 - Control Circuit for Starter Relay 2 
              P3049 00 [038] - Open Circuit
              Intermittent - Not Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 44632 km
                    Date: 2020.08.21
                    Time: 01:05:50
                    Engine speed: 780.75 /min
                    Normed load value: 29.4 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 83 °C
                    Intake air temperature: 35 °C
                    Ambient air pressure: 980 mbar
                    Voltage terminal 30: 13.440 V
                    Unlearning counter according OBD: 40
                    Engine speed: 781 /min
                    Vehicle speed: 0 km/h
                    Battery voltage: 13.4 V
                    Status of starter activation-FRF_ST_RL: 1
                    Sensor for engine block temperature: raw value       
                    Coolant temperature
                    Number of resets of main unit-CTR_RST_MC: 0
    Readiness: 0 0 0 0 0 
-------------------------------------------------------------------------
    Address 03: ABS Brakes (J104)       Labels:. 1K0-907-379-60EC1F.clb
       Part No SW: 1K0 907 379 BS    HW: 1K0 907 379 BS
       Component: ESP MK60EC1   H46 0166  
       Revision: 00H46001    
       Coding: 233F4012092300FBC41402E5901D0091A1000021
       Shop #: WSC 00049 770 00126
       VCID: 044485DF875B59A637-8050
    3 Faults Found:
    00668 - Supply Voltage Terminal 30 
            002 - Lower Limit Exceeded - Intermittent
                    Freeze Frame:
                    Fault Status: 00100010
                    Fault Priority: 1
                    Fault Frequency: 1
                    Reset counter: 53
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.20
                    Time: 13:24:13
                    Freeze Frame:
                    Count: 7
                    Count: 15
                    Count: 4608
                    Count: 128
                    Count: 27136
                    Count: 0
                    Count: 0
                    Count: 0
    01325 - Control Module for Tire Pressure Monitoring (J502) 
            004 - No Signal/Communication - Intermittent
                    Freeze Frame:
                    Fault Status: 00100100
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 54
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.19
                    Time: 20:52:04
N                   Freeze Frame:
                    Count: 2
                    Count: 14
                    Count: 4608
                    Count: 16390
                    Count: 41728
                    Count: 0
                    Count: 0
                    Count: 0
 
    00457 - Central Electronics Control Module / BCM (J519) 
            008 - Implausible Signal
                    Freeze Frame:
                    Fault Status: 01101000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 13
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.19
                    Time: 20:52:07
                    Freeze Frame:
                    Count: 0
                    Count: 14
                    Count: 4608
                    Count: 8262
                    Count: 41728
                    Count: 0
                    Count: 0
                    Count: 0
-------------------------------------------------------------------------
    Address 08: Auto HVAC
    Cannot be reached
-------------------------------------------------------------------------
    Address 09: Cent. Elect.
    Cannot be reached
-------------------------------------------------------------------------
    Address 10: Park/Steer Assist (J446)       Labels:. 3C8-919-475.clb
       Part No SW: 5P0 919 475 C    HW: 8P0 919 475 N
       Component: PARKHILFE 8K  H08 0008  
       Revision: --------    Serial number: 12531433900130
       Coding: 100002
       Shop #: WSC 00049 770 00126
       VCID: 3B363E23BA25E65E06-806E
    4 Faults Found:
    01543 - Parking Aid Warning Chime (H15) 
            009 - Open or Short to Ground - Intermittent
             Freeze Frame:
                    Fault Status: 00101001
                    Fault Priority: 3
                    Fault Frequency: 3
                    Reset counter: 55
                    Mileage: 0 km
                    Time Indication: 0
                    Freeze Frame:
                    Temperature: 17.0°C
    01625 - Front Parking Aid Warning Chime (H22) 
            009 - Open or Short to Ground - Intermittent
             Freeze Frame:
                    Fault Status: 00101001
                    Fault Priority: 3
                    Fault Frequency: 3
                    Reset counter: 55
                    Mileage: 0 km
                    Time Indication: 0
                    Freeze Frame:
                    Temperature: 17.0°C
    00446 - Function Limitation due to Under-Voltage 
            002 - Lower Limit Exceeded - Intermittent
             Freeze Frame:
                    Fault Status: 00100010
                    Fault Priority: 6
                    Fault Frequency: 2
                    Reset counter: 53
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.20
                    Time: 13:23:58
                    Freeze Frame:
                    Temperature: 21.0°C
    00466 - Control Module for Steering Column Electronics (J527) 
            004 - No Signal/Communication
                    Freeze Frame:
                    Fault Status: 01100100
                    Fault Priority: 6
                    Fault Frequency: 1
                    Reset counter: 13
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.19
                    Time: 20:52:04
                    Freeze Frame:
                    Temperature: 20.0°C
-------------------------------------------------------------------------
    Address 15: Airbags        Labels: 1K0-909-605.lbl
       Part No SW: 1K0 909 605 T    HW: 1K0 909 605 T
       Component: 0Z AIRBAG VW8   020 2300  
       Revision: 05020000    Serial number: 0038PD308DVI  
       Coding: 0012378
       Shop #: WSC 00049 770 00126
       VCID: 3D32303B6431E86E38-8068
       Subsystem 1 - Serial number: 6332MSME4A6A1722D
       Subsystem 2 - Serial number: 6342MSME4A6A1449K
       Subsystem 3 - Serial number: 6351HSME304E47458
       Subsystem 4 - Serial number: 6361HSME304E42454
    1 Fault Found:
    00532 - Supply Voltage B+ 
            002 - Lower Limit Exceeded - Intermittent
-------------------------------------------------------------------------
    Address 16: Steering wheel
    Cannot be reached
-------------------------------------------------------------------------
    Address 17: Instruments (J285)       Labels:* 1K0-920-xxx-17.lbl-SRI1
       Part No SW: 5P0 920 950 B    HW: 5P0 920 950 B
       Component: KOMBI         H02 0905  
       Serial number: 00000000000000
       Coding: 410B01
       Shop #: WSC 00049 770 00106
       ASAM Dataset: EV_Kombi_UDS_VDD_RM09 A04727
       ROD: EV_Kombi_UDS_VDD_RM09_SK46.rod
       VCID: 302C190F6B631506A3-8064
    4 Faults Found:
    12664832 - Function Restricted due to Missing Message(s) 
              U1111 00 [009] - -
              [Steuergerät für BCM / Bordnetz / el. ZE: keine 
              Kommunikation]
              Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 1
                    Reset counter: 13
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 20:54:06
    12718592 - Function Restricted due to Missing Message(s) 
              U1111 00 [009] - -
              [Steuergerät für Lenksäulenelektronik: keine Kommunikation]
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 23
                    Reset counter: 16
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 20:54:06
    13631488 - Function Restricted due to Missing Message(s) 
              U1111 00 [009] - -
              [Steuergerät für Komfortsysteme: keine Kommunikation]
              Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 22
                    Reset counter: 16
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 20:54:06
    13635840 - Supply voltage 
              U1011 00 [008] - Voltage too Low
              [Supply voltage too low]
              Intermittent - Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 9
                    Reset counter: 55
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 23:09:57
-------------------------------------------------------------------------
    Address 19: CAN Gateway (J533)       Labels:. 7N0-907-530-V2.clb
       Part No SW: 7N0 907 530 AQ    HW: 7N0 907 530 AL
       Component: J533  Gateway H58 1653  
       Revision:   H58       Serial number: 081214F1002090
       Coding: 352203
       Shop #: WSC 00049 770 00126
       VCID: 7F4E0A33EEBD3A7E6A-802A
    2 Faults Found:
    01336 - Company Data Bus for Comfort System 
            014 - Defective
             Freeze Frame:
                    Fault Status: 01101110
                    Fault Priority: 1
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.20
                    Time: 14:34:13
    00532 - Supply Voltage B+ 
            002 - Lower Limit Exceeded - Intermittent
             Freeze Frame:
                    Fault Status: 00100010
                    Fault Priority: 3
                    Fault Frequency: 6
                    Reset counter: 55
                    Mileage: 44613 km
                    Time Indication: 0
                    Date: 2020.08.20
                    Time: 14:45:42
-------------------------------------------------------------------------
    Address 25: Immobilizer (J334)       Labels:| 5K0-920-xxx-25.clb
       Part No SW: 5K0 953 234     HW: 5K0 953 234 
       Component: IMMO          H02 0905  
       Serial number:               
       Coding: 000000
       Shop #: WSC 00000 000 00000
       ASAM Dataset: EV_Immo_UDS_VDD_RM09 A03710
       ROD: EV_Immo_UDS_VDD_RM09_VW31.rod
       VCID: 6A98CB678D3FAFD6AD-803E
    No fault code found.
-------------------------------------------------------------------------
    Address 2E: Media Player 3
    Cannot be reached
-------------------------------------------------------------------------
    Address 37: Navigation (J794)       Labels:| 1K0-035-27x-37.clb
       Part No SW: 5P0 035 192 H    HW: 5P0 035 192 H
       Component: RNS315-EU   H85 0501  
       Serial number: SEZAZ2P0608483
       Coding: 040004010404000000000002
       Shop #: WSC 00049 770 00106
       ASAM Dataset: EV_RNS315EUV2UDS 001705
       ROD: EV_RNS315EUV2UDS.rod
       VCID: 312A1C0B60691C0EAC-8064
       Data medium: 
       Subsystem 1 - Part No: 3AA 919 866 
       Component: EUR_W_V7  0066 
    2 Faults Found:
    1048578 - Supply voltage 
              U1011 00 [008] - Voltage too Low
              [supply voltage lower limit exceeded]
              Intermittent - Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 3
                    Fault Frequency: 9
                    Reset counter: 55
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 23:10:28
    1048580 - Function Restricted due to Insufficient Voltage 
              U1400 00 [008] - -
              [restriction due to under voltage]
              Intermittent - Confirmed - Tested Since Memory Clear
                    Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 6
                    Fault Frequency: 8
                    Reset counter: 55
                    Mileage: 44613 km
                    Date: 2020.08.19
                    Time: 16:42:38
-------------------------------------------------------------------------
    Address 42: Door Elect, Driver
    Cannot be reached
-------------------------------------------------------------------------
    Address 44: Steering Assist        Labels: 1K0-909-14x-GEN3.clb
       Part No: 1K0 909 144 R
       Component: EPS_ZFLS Kl. 65     3501  
       Revision: 00H22000    
       Shop #: WSC 00049 770 00126
       VCID: 393A242B7019D44E14-806C
    No fault code found.
-------------------------------------------------------------------------
    Address 46: Central Conv.
    Cannot be reached
-------------------------------------------------------------------------
    Address 52: Door Elect, Pass.
    Cannot be reached
-------------------------------------------------------------------------
    Address 61: Battery Regul. (J840)       Labels:. 1K0-907-534.clb
       Part No SW: 7N0 907 534     HW: 7N0 907 530 AL
       Component: Batt.regelung H58 1653  
       Serial number: 081214F1002090
       Coding: 030F185A
       Shop #: WSC 00049 770 00126
       VCID: 71AADC0BA8E95C0EEC-8024
       Subsystem 1 - Part No SW: 1K0 915 181 H    HW: 1K0 915 181 A
       Component: J367-BDM  H07 0180 
       Serial number: 41344825511491186872
    No fault code found.
-------------------------------------------------------------------------
    Address 62: Door, Rear Left
    Cannot be reached
-------------------------------------------------------------------------
    Address 72: Door, Rear Right
    Cannot be reached
End----------(Elapsed Time: 00:50, VBatt start/end: 14.0V/14.0V)---------
So far, new AGM battery, power relays, central electrics system and CAN BUS-no different... I can't even get into the central electrics to code it!