Seat Altea Oxygen Sensor Heater Failure

Oxygen sensor heater failure on a 2012 Altea, eh? First, confirm which O2 sensor is throwing the code. There are usually two: pre-cat (before the catalytic converter) and post-cat (after the catalytic converter). Knowing which one will save you time and money. Also, before condemning the sensor, perform some basic sensor testing with a multimeter. Check for voltage at the heater circuit connector when the engine is running. No voltage indicates a wiring issue upstream. A visual inspection of the wiring harness and connector is crucial. Look for corrosion, damaged wires, or loose connections, particularly near the exhaust system where heat can degrade the insulation. Have you scanned for any other related DTCs?

Thanks for the quick response. I only have a basic OBD2 scanner, and it just gives me the generic 'Oxygen Sensor Heater Circuit Malfunction' code. How would I go about determining specifically which sensor is faulty and how do I test the voltage at the heater circuit?

Okay, a generic code makes pinpointing the sensor trickier. You'll need a scanner that can read live data or access manufacturer-specific codes. However, since you suspect a wiring issue, focus on that first. Locate both pre-cat and post-cat O2 sensors along the exhaust system. Visually inspect their wiring and connectors for damage. To test the heater circuit, you'll need a multimeter. Disconnect the sensor connector and, with the ignition on, probe the heater circuit terminals in the harness connector (refer to your car's wiring diagram for pin identification). You should see battery voltage (around 12V). No voltage confirms a break in the wiring. While a faulty sensor is possible, your initial assessment of a wiring or connector problem is plausible, given the age of the vehicle and its exposure to the elements. If you are not comfortable with sensor testing, take your vehicle to a workshop.

Thank you for confirming my suspicions and providing such detailed information. I took it to my local mechanic, and you were spot on - a faulty connection. 95€ later and the Altea is running smoothly again. No more check engine light and hopefully better fuel economy!