P0135 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0135 on a Audi means the internal heater element of your upstream (Bank 1, Sensor 1) oxygen sensor has failed, so the sensor warms up too slowly and the engine delays entering closed-loop fuel control. The most common cause is simple heater wear inside the sensor. Because this pre-catalyst sensor sets the air-fuel mixture, you mainly notice a check engine light and worse cold-start fuel economy. A replacement upstream O2 sensor costs roughly 100 to 300 EUR including labour, or up to about 400 EUR with an OEM-quality part. VW, Audi, Skoda and SEAT apps often show this code as P013500; the last two digits are a failure-type byte.
- Severity
- Low · Emissions
- Typical repair cost, all makes
- €1-€400
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Audi and Skanyx tells you what P0135 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0135 mean on a Audi?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0135.
Audi A4
2008-2024
The A4 shares the EA888 family with the Golf, so the upstream Bosch sensor lives in the hot turbo downpipe and suffers the same oil-consumption contamination on higher-mileage 2.0 TFSI units. Longitudinal engine layout makes the sensor harder to reach than on the transverse Golf, so independent-shop labour tends to run higher. Confirm petrol versus diesel, since the sensor location differs.
What causes P0135 on a Audi?
Beyond the generic causes listed on the main P0135 page, these are the patterns noted for Audi models:
EA888 2.0 TFSI oil consumption contaminating the upstream sensor
: Audi A4
Tight longitudinal engine-bay access raising labour time
: Audi A4
How to diagnose P0135 on a Audi with OBD2
Follow these steps to pinpoint the root cause of P0135:
- Read all stored codes and note whether other heater codes (P0141, P0155, P0161) are present. Multiple heater codes together usually point to a shared fuse, relay, or wiring fault rather than one sensor
- Locate and check the O2 sensor heater fuse in the fuse box. Replace it if blown and recheck before condemning the sensor
- Unplug the Bank 1 Sensor 1 connector and measure heater resistance across the two heater pins. A healthy heater reads roughly 2-15 ohms. An open circuit (infinite reading) means the element has burned out, under 1 ohm suggests a short
- Inspect the connector and pins for corrosion, melting, bent terminals, or water intrusion, and clean or repair as needed
- Back-probe the connector with the key on and check for battery voltage on the heater supply wire. No voltage points to a fuse, relay, or wiring fault upstream of the sensor
- Inspect the sensor wiring along its full run for chafing or melting against the exhaust manifold and heat shields, then clear the code and confirm it does not return
How much does P0135 cost to fix on a Audi? (EUR)
Estimated repair costs for P0135 in EUR, compiled across makes. Expect Audi parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace O2 sensor heater fuse | €1–€3 | €0–€0 | €1–€3 | Easy |
| Replace upstream O2 sensor (Bank 1) | €50–€180 | €50–€120 | €100–€300 | Moderate |
| Repair wiring or connector | €5–€20 | €40–€120 | €45–€140 | Moderate |
| Replace O2 sensor (OEM quality) | €80–€280 | €50–€120 | €130–€400 | Moderate |
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0135
These codes are often seen alongside P0135 or point to related issues, on any make:
Looking for the full P0135 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0135 guide
Diagnose P0135 on your Audi
Your car logged P0135. Skanyx reads it on a standard OBD2 adapter (Bluetooth LE on iPhone), tells you whether it is safe to keep driving, and shows the €1-€400 repair range so you know the number before a shop quotes you. Free on iPhone and Android, and you do not need to be a mechanic to read it.
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