2003 S6 - Oxygen Sensor Issues (2003 S6)

[Uwe]

The 2nd hand ABS module i installed was identical part number so i am assuming no coding is required as there are no faults in the ABS module now that the car is able to communicate with it. Or am i incorrect

Yes, the ABS looks happy now.

I'm not sure why 01-Engine is complaining about Missing Messages though.

-Uwe-

 

[atbro199]

Hello, new member here. Just picked up an 03 S6 a month ago and have been trying to get the emissions sorted out so I can take it for an emissions test and fully register it.

For context: the car came with the cats removed, oxygen sensor spacers used and the MIL was on. I had a local shop install two Magnaflow direct-fit pipes with cats. Spacers removed and oxygen sensors installed as intended. MIL was still on. The code was regarding B2S2 internal resistance too high, P1140.

I installed a brand new Bosch 16073 sensor on B2S2 to help resolve this issue but it persists.

I believe this is an electrical issue, not the sensor as it is brand new and the old sensor was throwing the same code. I switched OXS connectors under the hood with B1S2 and the code persisted still on B2S2. The voltage to B2S2 stays constant the entire time and the TEST never begins, while B1S2 receives OK status. Also the B2S2 resistance is HIGH.

Here is my auto scan (a little old but I had to battle an EVAP issue I have since resolved):

Thursday,15,August,2024,18:39:13:42314
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 24.7.0.0 (x64)
Data version: 20240715 DS356.3
www.Ross-Tech.com


VIN: WAUXU64B43N116243   License Plate:



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 4B (4B - Audi A6/S6/RS6/allroad C5 (1998 > 2005))
Scan: 01 02 03 06 08 15 16 17 18 22 34 35 36 37 45 55 56 57 65 67
          75 76 77
 
VIN: WAUXU64B43N116243  
-------------------------------------------------------------------------------
Address 01: Engine        Labels: 077-907-559-ANK.clb
   Part No: 4D0 907 560 CN
   Component: 4.2L V8/5V      G   0001
   Coding: 06752
   Shop #: WSC 24253
   VCID: 74E783CC441E6536D7-5140
   WAUXU64B43N116243     AUZ7Z0C2391716

1 Fault Found:
17548 - Oxygen (Lambda) Sensor; B2 S2
            P1140 - 35-00 - Internal Resistance too High
Readiness: 0110 1001

-------------------------------------------------------------------------------
Address 02: Auto Trans        Labels: 01L-927-156.lbl
   Part No: 4B0 927 156 FH
   Component: AG5 01L 4.2l5V  USA 1314
   Coding: 00002
   Shop #: WSC 02334
   VCID: 72EB85D43E0A6B06C5-515E

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 4B0-614-517.lbl
   Part No: 4B0 614 517 E
   Component: ABS/ESP allrad      3428
   Coding: 06397
   Shop #: WSC 31414
   VCID: 2345B090B170B28EFE-5140

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC        Labels: 4B0-820-043-MY2.lbl
   Part No: 4B0 820 043 AR
   Component: A6-Klimavollautomat 0208
   Coding: 00010
   Shop #: WSC 00000
   VCID: 6ADB9DB416DAA3C67D-2586

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 4B0-959-655-AI84.lbl
   Part No: 4B0 959 655 Q
   Component: Airbag 8.4EP        3001
   Coding: 0000607
   Shop #: WSC 02334 785 00200
   VCID: 3E7361E46AD2FF66F1-515E

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments        Labels: 4B0-920-xxx-17.lbl
   Part No: 4B0 920 981 Q
   Component: KOMBI+WEGFAHRS. VDO D12
   Coding: 03283
   Shop #: WSC 62859
   VCID: 346743CC049E253617-5140
   WAUXU64B43N116243     AUZ7Z0C2391716

3 Faults Found:
00667 - Ambient Temperature Signal
            30-10 - Open or Short to Plus - Intermittent
01300 - Control Module for Navigation with CD-Rom (J401)
            49-10 - No Communications - Intermittent
01304 - Radio
            49-00 - No Communications

-------------------------------------------------------------------------------
Address 35: Centr. Locks        Labels:. 4B0-962-258.clb
   Part No: 4B0 962 258 M
   Component: Central Lock/Alarm  D38
   Coding: 15977
   Shop #: WSC 02334
   VCID: 336540D00190220E0E-4F06

3 Faults Found:
01559 - Drivers Door
            59-10 - Can't Unlock - Intermittent
01561 - Rear left door
            59-10 - Can't Unlock - Intermittent
01562 - Rear right door
            59-00 - Can't Unlock

-------------------------------------------------------------------------------
Address 36: Seat Mem. Drvr        Labels: None
   Part No: 4B0 959 760 B
   Component: Sitzmemory R1 F     0204
   Coding: 00001
   Shop #: WSC 00000
   VCID: 2C575BACDCAE7DF64F-4B1A

1 Fault Found:
00668 - Supply Voltage Terminal 30
            07-10 - Signal too Low - Intermittent

-------------------------------------------------------------------------------
Address 37: Navigation        Labels: 4B0-919-887-BNS4.lbl
   Part No: 4B0 919 887 E
   Component: BNS 4.2 H05    BNO 0050
   VCID: 35617EC80FE43C3E20-4AE8

1 Fault Found:
65535 - Internal Control Module Memory Error
            00-00 - -

-------------------------------------------------------------------------------
Address 55: Headlight Range        Labels: 4Z7-907-357.lbl
   Part No: 4Z7 907 357
   Component: dynamische LWR       D09
   Coding: 00050
   Shop #: WSC 02334
   VCID: 0407D30C14BE55B6E7-4B4C

No fault code found.

End-------------------------(Elapsed Time: 05:17)--------------------------

Here are some more information I captured based upon my basic knowledge:

Thursday,22,August,2024,20:15:33:42314
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 24.7.0.0 (x64)
Data version: 20240715 DS356.3
www.Ross-Tech.com

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


                Address 01: Engine  (4D0 907 560 CN)

20:15:30 Group 036: Lambda Control (Sensor Readiness - After Catalyst)
  0.635 V  Sensor Voltage Bank 1 Sensor 2
  B1-S2 OK  Result Lambda Availability
  0.410 V  Sensor Voltage Bank 2 Sensor 2
  Test OFF  Result Lambda Availability

20:15:30 Group 038: Lambda Control (Delta Lambda Bank 2)
  24.1 %  Engine Load
  0.420 V  Sensor Voltage Bank 2 Sensor 2
  0.0 ms  Adjustment Bank 2 Sensor 2
  Test OFF  Result Delta Lambda B2

20:15:30 Group 042: Lambda Control (Lambda Sensor Heating Bank 2)
  0.40 kOhm  Resistance Bank 2 Sensor 1
  Htg. S1 ON  Heater Condition Bank 2 Sensor 1
  25.50 kOhm  Resistance Bank 2 Sensor 2
  Htg. S2 ON  Heater Condition Bank 2 Sensor 2

Any advice? I am a newbie with VCDS and automotive electrical, but I do have a multi-meter. Thanks.

 

[atbro199]

How can I test the ECU and the wiring between it and the firewall?

 

[atbro199]

OP, how'd you run your diagnosis of the wiring and ECU? I am a wiring newb but I believe I have a similar problem as you, with my 03 S6.

Moderator's note: This referenced @Coopkaedin240 in this thread.

 

[PetrolDave]

How can I test the ECU and the wiring between it and the firewall?

With a wiring diagram (that's a link) and your multimeter.

 

[Crasher]

ONCE, a long time ago, I did a Passat 1.8T that refused to accept anything other than a genuine VW sensor. A unusual fact on these is the pre and post cat sensors are the same part number 1K0 998 262 AB and I don’t recall seeing that before. The Bosch part number is 0 258 010 073 with the trade numbers LS 10073 and LSF-4.2. I can’t find a Bosch 16703 but searching in Tec Doc under Lambda sensors gives MTE, KAWE, TISCAN and VEMO which are sensors for VAG but according to MTE, equivalent to

OE number	Reference info
077906265S
077906265AA
077906265R
077906265AF
077906265P
078906265Q
077906265L
1K0998262AB
077906265K

So in theory it is correct but Bosch don’t list it that way, highly confusing.

 

[atbro199]

With a wiring diagram (that's a link) and your multimeter.

I have a Bentley manual, so I have access to wiring diagrams. Can you please confirm to me that I need to test pins 6, 10, and 11 for the B2S2 sensor at the ECU? Also, how would I test the voltage that is measured in VCDS since it never really goes above ~0.41? Is that the heating circuit voltage (white wires) or the gray signal wire?

 

[atbro199]

ONCE, a long time ago, I did a Passat 1.8T that refused to accept anything other than a genuine VW sensor. A unusual fact on these is the pre and post cat sensors are the same part number 1K0 998 262 AB and I don’t recall seeing that before. The Bosch part number is 0 258 010 073 with the trade numbers LS 10073 and LSF-4.2. I can’t find a Bosch 16703 but searching in Tec Doc under Lambda sensors gives MTE, KAWE, TISCAN and VEMO which are sensors for VAG but according to MTE, equivalent to

OE number	Reference info
077906265S
077906265AA
077906265R
077906265AF
077906265P
078906265Q
077906265L
1K0998262AB
077906265K

So in theory it is correct but Bosch don’t list it that way, highly confusing.

I saw you typed 16703, not 16073. With the car getting older, harder to find specific parts.

I'm letting the car cool off and then I'll get in there to do some measuring.

 

[Coopkaedin240]

OP, how'd you run your diagnosis of the wiring and ECU? I am a wiring newb but I believe I have a similar problem as you, with my 03 S6.

So you’re going to want to un plug the wiring harness to the ecu, and the oxygen sensor. Then you are going to check which pins on the ecu connector lead to the oxygen sensor. (Wiring diagram) Then just check resistance of said wires. ohms shouldn’t be higher than like 0.5 ohms depending on the multimeter you use.

Are you having the same fault?

 

[Crasher]

Thankfully I had entered the number correctly in Tec Doc so the info is valid.

 

[PetrolDave]

Can you please confirm to me that I need to test pins 6, 10, and 11 for the B2S2 sensor at the ECU?

Since I don't own a 2003 S6 there's no way I can confirm that, do you not believe the Bentley wiring diagrams? If not then the link I posted is to the factory information on erwin.

 

[Dr Sheldon]

How can I test the ECU and the wiring between it and the firewall?

What is a Firewall ??

Those wires go back to ECU - They must because the ECU can make a resistance measurement !!

Look on ERWIN - it will show you all the connectors that the wiring runs through !!

 

[atbro199]

So you’re going to want to un plug the wiring harness to the ecu, and the oxygen sensor. Then you are going to check which pins on the ecu connector lead to the oxygen sensor. (Wiring diagram) Then just check resistance of said wires. ohms shouldn’t be higher than like 0.5 ohms depending on the multimeter you use.

Are you having the same fault?

Edit: sorry I meant to put this in my post in the tech forum:

2003 S6 - Oxygen Sensor Issues (2003 S6)

Hello, new member here. Just picked up an 03 S6 a month ago and have been trying to get the emissions sorted out so I can take it for an emissions test and fully register it. For context: the car came with the cats removed, oxygen sensor spacers used and the MIL was on. I had a local shop...

forums.ross-tech.com

Before I pulled the ECU out I unplugged both the B2S2 and B1S2 sensors (brown and green connectors respectfully), using the multimeter I measured 20.0 or 19.7ish on the two white wires, even when reversed. That doesn't seem correct as the ECU read B1S2 as OK. Here is a picture to confirm:

https://imgur.com/8c6CBCs

 

[atbro199]

Before I pulled the ECU out I unplugged both the B2S2 and B1S2 sensors (brown and green connectors respectfully), using the multimeter I measured 20.0 or 19.7ish on the two white wires, even when reversed. That doesn't seem correct as the ECU read B1S2 as OK. When I measured it the car was slightly warm. Here is a picture to confirm:

https://imgur.com/8c6CBCs

 

[Uwe]

using the multimeter I measured 20.0 or 19.7ish on the two white wires, even when reversed. That doesn't seem correct

I think you're measuring the resistance of the heater in the sensor? Why do you think that's incorrect?

-Uwe-

 

[atbro199]

I think you're measuring the resistance of the heater in the sensor? Why do you think that's incorrect?

-Uwe-

I believe I am, yes. I've been researching this issue for weeks now and I haven't gotten very far and this car's registration dies at the end of the month if I cannot get it to pass emissions. I've only had it for a month.

I'm measuring this because I don't know what else to do with my multimeter. I want to measure the heater and signal wires between the ECU and the sensors themselves but once I got the ECU cover off, I don't feel comfortable getting the ECU out of the metal shear bolts on my own. I'm not knowledgeable with electrical and dont want to screw it up.

Ideally I think the wire to measure is the B2S2 signal wire, assuming that is what the ECU uses to measure resistance and what I see in VCDS.

The car came with no cats and with spacers installed, also had a MIL. I read that bad O2 sensor could damage the ECU, hence my reply to this thread. I have since replaced the B2S2 sensor with Bosch 16073 and I can only assume it is good, but I don't know how to test it.

Lastly, I reset the DTCs two days ago and have been driving it. I don't have the P1140 code yet but I do have an EVAP purge valve code.. a new one is on order.

 

[Coopkaedin240]

Wait did you put oem cats on the vehicle?

Easiest way to get that ecu out is to take a die grinder to the heads hot and make it like a - across the whole bolt to fit a big flat head screwdriver and make sure to unscrew it fast but be careful the bolts going to be hot.

If you aren't comfortable with that, I understand it is a vital component and can be scary.

If you put oem cats on the vehicle and are still getting a code and haven't replaced the sensor, it is probable that the 02 sensor is bad, it is highly unlikely that the ECU driver will fail but with that being said I have seen it twice in the past year. I would recommend replacing the 02 sensor if the code comes back. Also an auto scan would be helpful if the code returns.

 

[atbro199]

Wait did you put oem cats on the vehicle?

Easiest way to get that ecu out is to take a die grinder to the heads hot and make it like a - across the whole bolt to fit a big flat head screwdriver and make sure to unscrew it fast but be careful the bolts going to be hot.

If you aren't comfortable with that, I understand it is a vital component and can be scary.

If you put oem cats on the vehicle and are still getting a code and haven't replaced the sensor, it is probable that the 02 sensor is bad, it is highly unlikely that the ECU driver will fail but with that being said I have seen it twice in the past year. I would recommend replacing the 02 sensor if the code comes back. Also an auto scan would be helpful if the code returns.

Thanks for the reply.

Unfortunately they are not OEM... I couldn't find any new ones and I didn't want to put used 20ish year old ones on. The pair I bought are Magnaflow direct-fit CARB compliant. They are the complete pipe so no welding or cutting required. They're brand new and I'd be happy if they last me four more years until the car is 25 years old so I can register it as historic.

I do have one more brand new Bosch 16073 that I'll swap in on Monday just to see if the voltage and resistance measured in VCDS match the other bank, which is ok. I want to swap out the brown "tabbed" connector with the generic black "D" connector that Bosch supplied but I need a better tool to take the pins out, and that tool comes on Monday. I'm not confident that jamming the non-tabbed black D connector into the brown tabbed "D" connector is the issue (which is what the PO did and is what I'm doing now, connection appears good) but it'll help set a better baseline.

All else fails I'll take it to a local speed shop but I don't want to keep throwing money at this car.

 

[Crasher]

What is a Firewall ??

Seriously?

 

[Dr Sheldon]

Seriously?

Indeed yes !! WTF is a Firewall in a car ??