O2 Sensor B1S1 - Internal Resistance too High, Intermittent, Is 02 Sensor Bad?

[Currancchs]

Car is an '01 Audi TT, I have been experiencing an intermittent rough idle, with very occasional "Popping" sound from the exhaust... The car is also only putting out about 10 psi of boost, and the ECU is calling for roughly 15 psi... Not sure if the issues are related.

Readings taken during a quick drive after the car warmed up this afternoon showed the front 02 sensor resistance ~0.6-0.7 KOhms, and the post cat was 0.1-0.3 KOhms (No related trouble code). Voltages for the pre-cat were sporadic, from 0.125-0.895v.

Also of note, the internal resistance measurement for the pre cat sensor stopped displaying about 5 minutes into the ride, does this signify a fault, or may the heater have just turned off?

Lastly, when the car is shut off when idling roughly it has (Twice in 4 months) dieseled, or continued to run roughly with key off for ~4-10 seconds... Again, not sure if related, any insight is appreciated. Thanks!

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SOLVED

The problem was a combination of bad primary O2 and a massive vacuum/boost leak coming from the brake booster line as it runs under the front portion of the intake manifold, blew as soon as pressurized (and no, it was not over pressurized) lean fuel trim caused check engine light 5 minutes before pressure test!

[Dana @ Ross-Tech]

Please post the Auto-Scan from this vehicle and the info from measuring block 032 as described here: Fuel Trim Info

[Currancchs]

Thanks for your quick response, My Block 032 measurements are 4.3% @ Idle and 6.3% @ Part Throttle. The Auto Scan Results are below.

VCDS Version: Release 10.6.3 (x64)
Data version: 20101206

Monday,07,March,2011,07:59:44:51317

Chassis Type: 8N - Audi TT
Scan: 01 02 03 08 15 17 22 35 37 45 55 56 76 77

-------------------------------------------------------------------------------
Address 01: Engine Labels: 06A-906-032-AMU.lbl
Part No: 8N0 906 018 T
Component: 1.8L R4/5VT G 0003
Coding: 06710
Shop #: WSC 01236
VCID: 428587D06409

1 Fault Found:
17521 - Oxygen (Lambda) Sensor; B1 S1: Internal Resistance too High
P1113 - 35-10 - - - Intermittent
Readiness: 0000 1000

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 8N0-907-379-MK20-E.lbl
Part No: 8N0 907 379 E
Component: ESP 20 CAN V004
Coding: 18446
Shop #: WSC 01236
VCID: 3E7DF32010F1

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: None
Part No: 8N0 820 043 A
Component: TT-KLIMAVOLLAUTOMAT D03
Coding: 00140
Shop #: WSC 01236
VCID: 28513578E275

1 Fault Found:
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to Plus - Intermittent

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 8N8-909-601.lbl
Part No: 8N8 909 601
Component: Airbag Front+Seite 1005
Coding: 10102
Shop #: WSC 01236
VCID: F7F3A604FF4B

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 8Nx-920-xxx-17.lbl
Part No: 8N1 920 930 E
Component: KOMBI+WEGFAHRS. M73 D08
Coding: 02244
Shop #: WSC 00000
VCID: 336BD2142BB3

No Faults Found
or DTCs not supported by controller
or a communication error occurred

-------------------------------------------------------------------------------
Address 22: AWD Labels: 02D-900-554.lbl
Part No: 02D 900 554 B
Component: HALDEX LSC ECC 0006
VCID: 1F432EA4B73B

No fault code found.

-------------------------------------------------------------------------------
Address 35: Centr. Locks Labels: 8Nx-962-267.lbl
Part No: 8N7 962 267 A
Component: Central Lock/Alarm D05
Coding: 15900
Shop #: WSC 00000
VCID: 3E7DF32010F1

1 Fault Found:
01370 - Alarm triggered by Interior Monitoring
35-00 - -

-------------------------------------------------------------------------------
Address 45: Inter. Monitor Labels: 8E0-951-177.lbl
Part No: 8N7 951 177
Component: Innenraumueberw. D14
Coding: 00001
Shop #: WSC 00000
VCID: FBFBBA34C363

No fault code found.

-------------------------------------------------------------------------------
Address 55: Xenon Range Labels: 4B0-907-357-AUT.lbl
Part No: 4B0 907 357
Component: LEUCHTWEITEREGLER D004
Coding: 00010
Shop #: WSC 01236
VCID: E5CFFC4C55E7

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio Labels: 8D0-035-1xx-56.lbl
Part No: 8N0 035 186 A
Component: Radio D05
Coding: 00017
Shop #: WSC 01236
VCID: 2E5DC360C091

No fault code found.
End ---------------------------------------------------------------------

[stan067]

Usually if the O2 wiring is good I replace the sensor for this code. Good Luck

[Currancchs]

I got the O2 sensor today, will install this weekend and let you know if it clears things up. Interestingly I replaced my N75 this past weekend and went from getting ~10.5 psi to about 13.0 psi and ~170 HP to ~205 according to Vag-com, so making my way towards getting her to run correctly at least