P0135 on 2010-2012 Audi S5 Cabriolet: O2 Sensor Heater Fault Causes and Fixes

What's Unique About the 2010-2012 Audi S5 CABRIOLET

The 2010-2012 Audi S5 Cabriolet uses the 3.0L TFSI supercharged V6 engine, a powerplant shared with many other Audis of the era like the S4, A6, and Q5. On this V6 engine, 'Bank 1' refers to the passenger side of the engine. Therefore, P0135 specifically points to the upstream (pre-catalytic converter) O2 sensor on the passenger side. While the failure is typical for any car, accessing the sensor and its connector can be tight on this packed engine platform. On the passenger side, the air intake box may need to be removed for better access. A video showing the replacement on a similar 3.0T platform confirms the tight access and shows the connector is tucked up high. The connector 🎬 Watch this walkthrough for accessing the tight passenger side sensor. itself clips into a metal channel which can be difficult to reach and manipulate.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on.
• Reduced fuel economy.
• Possible rough idle, especially when the engine is cold.
• Failure to pass an emissions test.
• Vehicle may enter a 'limp mode' with reduced power if other related codes are present.

Most Likely Causes

1. Failed Oxygen Sensor Heater Element 🔴 High Probability Oxygen sensors are wear-and-tear items exposed to extreme heat and exhaust gases, causing the internal heater element to burn out over time. Oil leaks from valve cover gaskets can also drip onto the sensor or its wiring, causing premature failure, a known issue on some 3.0T engines.
   How to confirm: Disconnect the sensor and measure the resistance between the two heater circuit wires (often the two wires of the same color). An open circuit (infinite resistance or 'OL' on a multimeter) confirms the heater has failed. 🎬 See how to diagnose and fix a P0135 heater circuit fault. A good sensor will have a low resistance, typically between 2 and 20 ohms.
   Typical fix: Replace the Bank 1, Sensor 1 oxygen sensor.
   Est. part cost: $70-$250
2. Damaged Wiring or Corroded Connector 🟡 Medium Probability The wiring harness for the O2 sensor is located in the hot engine bay and under the vehicle, making it susceptible to heat damage, melting, or corrosion from road salt and moisture. The plastic connectors can become brittle and break during removal.
   How to confirm: Visually inspect the entire length of the sensor's wiring and the connector pins for any signs of melting, fraying, breaks, or green/white corrosion.
   Typical fix: Repair the damaged section of the wire or clean/replace the connector. If the connector is oil-soaked, it should be thoroughly cleaned with electrical contact cleaner.
   Est. part cost: $5-$50
3. Blown or Corroded Fuse for Heater Circuit ⚪ Low Probability
   How to confirm: Check fuse boxes in the instrument panel (left and right sides) and the engine bay plenum chamber (under the plastic cover near the windshield wipers). 🎬 Watch this guide to find hidden Audi O2 sensor fuses. The specific fuse for the O2 sensor heater is not always clearly labeled but may be shared with other engine components. Inspect for a blown fuse or, more subtly, for corrosion on the fuse contacts which can cause an open circuit.
   Typical fix: Replace the blown fuse or clean the corroded contacts. If the fuse blows again, a short circuit in the wiring or sensor must be diagnosed.
   Est. part cost: $1-$5

Rare But Worth Checking

• Exhaust Leak: A significant exhaust leak before the O2 sensor can allow fresh air to enter the exhaust stream, causing erratic readings. While this is less likely to cause a specific heater circuit fault like P0135, it can trigger other related O2 sensor codes.
• Powertrain Control Module (PCM) Fault: In very rare cases, the driver circuit within the PCM that controls the O2 sensor heater can fail. This should only be considered after all other possibilities have been exhaustively ruled out.

Diagnosis Steps

1. Use an OBD-II scanner to confirm P0135 is the active code and check for any other related codes.
2. Locate the Bank 1, Sensor 1 (Upstream) oxygen sensor. On the 3.0L V6, this is on the passenger side, before the catalytic converter. You may need to remove the airbox for better access.
3. Visually inspect the sensor's wiring harness and connector for any signs of melting, chafing, oil contamination, or corrosion.
4. Check the fuse for the O2 sensor heater circuit. This may be in the fuse panels on either side of the dashboard or in the plenum chamber fuse box under the hood.
5. If the wiring and fuse are okay, disconnect the sensor. Use a multimeter set to Ohms (Ω) to measure the resistance between the two heater pins on the sensor side of the connector (usually the two wires of the same color). A reading of 'OL' or infinite resistance indicates a failed heater element. A good heater will typically have a low resistance, between 2-20 Ohms.
6. With the key on and engine off, use a multimeter set to DC Volts to check for battery voltage at the heater power wire in the harness-side connector. You should also check for a good ground on the corresponding ground pin.
7. If voltage and ground are present at the harness and the sensor's heater resistance is infinite, the oxygen sensor is faulty and needs to be replaced. An O2 sensor socket (22mm or 7/8") is highly recommended for removal.

Parts You'll Likely Need

• Upstream Oxygen Sensor (Bank 1) (OEM #06E906265S (or latest revision)) — This is the component that contains the heater element reported as faulty by code P0135. The internal heater is the most common point of failure.
  Trusted brands: Bosch (often the OEM supplier), NTK, Denso
  OEM price range: $180-$250
  Aftermarket price range: $70-$150

Related Codes That Often Appear With This One

• P0134 — O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1). This can occur if the sensor isn't heating up and therefore isn't producing a signal.
• P1196 — As cited in NHTSA TSB #01139020337671, this manufacturer-specific code for an O2 sensor heater circuit fault can appear alongside P0135, indicating a confirmed issue pattern recognized by Audi.
• P1197 — Also cited in NHTSA TSB #01139020337671, this is another related manufacturer-specific heater circuit code that points to the same underlying problem.
• P0030 — This is the generic equivalent of P0135, also indicating an O2 Sensor Heater Control Circuit fault for Bank 1, Sensor 1. Some scanners may show both.

Technical Service Bulletins (TSBs) & Recalls

• 01139020337671 / 01 13 90: MIL on (DTC P1196/P1197/P0135, heater circuit fault lambda sensor) - Repair Authorization

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB #01139020337671) was issued for the 2010 model year concerning a MIL-on condition with DTC P0135, P1196, or P1197, all related to lambda sensor heater circuit faults, indicating a known issue. The TSB is a 'Repair Authorization', suggesting it's a known warranty or dealer-level repair pattern.
• Owners on forums like Audizine frequently report this code. The consensus is that replacing the sensor with an OEM or direct-fit Bosch unit (like the 17351) is the definitive fix. Many advise against using universal sensors that require splicing wires.
• Access to the passenger side sensor is noted to be tight. A common DIY approach involves removing the air intake snorkel and box to create more room to work from above.

Mechanic-Grade Diagnostic Values

• O2 Sensor Heater Element Resistance — expected: 2.0 - 20.0 Ohms. Failure: Open circuit ('OL' or infinite resistance) or resistance outside the specified range.
• VCDS Live Data - Heater Resistance — expected: Value should be stable and within spec (e.g., < 0.02 kOhm).. Failure: Value is excessively high, erratic, or shows 'Test Failed'.

Hidden / Shadow Codes Worth Checking

• VCDS Measuring Block 263: This is not a trouble code, but a specific live data block in VCDS software that allows a technician to directly read the calculated resistance of the Bank 1, Sensor 1 lambda probe heater. (see via Using VCDS (VAG-COM) diagnostic software, navigate to Engine (01) -> Measuring Blocks -> Group 263.)

Scan Tool Commands That Help

• VCDS (VAG-COM) or equivalent (e.g., Snap-on): Engine (01) -> Basic Settings -> Group 041 — This function actively tests the oxygen sensor heaters. The tool commands the heaters on and monitors their resistance, providing a clear pass/fail result without having to manually measure with a multimeter.

Wiring & Ground Locations

• O2 Sensor Heater Fuse — Potentially in the fuse box in the engine compartment plenum chamber, located under the plastic cover near the base of the windshield. Also check panels on the left and right sides of the dashboard.. A blown or, more subtly, a corroded fuse in this location can interrupt power to the heater circuit, causing P0135 even with a good sensor. This is often overlooked.
• Engine Ground Point — There is a primary engine ground point on the right side of the engine compartment, near the alternator.. A poor engine ground can cause a variety of electrical issues, including erratic sensor behavior. While not a direct cause of a heater circuit fault, ensuring this ground is clean and tight is a good practice during electrical diagnosis.
• B1S1 Connector Bracket — The electrical connector for the Bank 1 Sensor 1 O2 sensor is clipped into a small metal channel/bracket high up on the passenger side of the transmission bell housing area.. Knowing the connector is in a fixed bracket is key for removal. It doesn't just hang freely. Technicians need to slide it off the bracket before they can unplug it, which can be difficult to do by feel.

Real Owner Repair Stories

• RANS87IROCZ on YouTube (2008 Audi Q7 4.2L (different engine but similar Audi electrical design)) — Check engine light with codes for both downstream O2 sensor heater circuits (P0055, P0085) immediately after installing new sensors.
  ❌ Tried (didn't work) Replacing both downstream oxygen sensors.
  ✅ What actually fixed it The fuses for the O2 sensor circuits, located in the engine compartment plenum box, were not blown but were heavily corroded on the contacts. Cleaning the corrosion and reinstalling the fuses resolved the codes.

OEM Part Supersession History

• 06E906265F → 06E906265S — Standard part revision for improved performance, reliability, or manufacturing change.
  Heads up: The newer part number (06E906265S) is the correct replacement for the older one.

Model Year Variations Within This Range

• 2010-2012: No significant variations affecting this specific fault were found within the 2010-2012 model years for the S5 Cabriolet. The 3.0L TFSI V6 engine was used consistently in the Cabriolet throughout this period, while the Coupe model used a different (4.2L V8) engine until the 2013 model year facelift.