U0686Lost Communication With Catalyst Temperature Bank 2 Sensor 1
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Bank 2 exists only on engines whose cylinder rows feed separate exhaust paths, so U0686 belongs to V or flat engines with one converter per side. It means the first catalyst temperature probe of that second bank has stopped delivering digital messages. Such probes are often a thermocouple paired with a small electronics unit; Sensience, for example, sells N-type probes rated to 1000 °C whose module converts the reading to SENT or CAN. The module and its lead sit close to hot exhaust parts, which makes heat damage a typical cause. None of the carmakers describes this code in public material. The analog equivalents are P0435 to P0438; the same position on bank 1 is U0684. CARB requires a dedicated code once a digital input goes mute.
- What you may notice
- Check engine light
- Catalyst monitor for bank 2 not completed
- Likely causes
- LikelySensor electronics on bank 2 damaged by heat
- PossibleHarness on the bank 2 side chafed or melted
- PossibleConnector corroded
- RareEngine controller input fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.