The vehicle bus reports loss of communication with smart catalyst temperature sensor on bank 2 sensor 2. Catalyst protection and light-off monitoring switch to model-based estimates.
Medium severity. Can I keep driving?It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Most likely causes
- Bus wiring open or shorted
- Module without power or ground
- Module failed
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of U0687 means
- U: Communication network
- 0: Generic code: same on every make
- 6: Subsystem depends on the code range
- 87: Specific fault in that system
Frequently asked questions
Can I keep driving with code U0687?
It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
What causes code U0687?
The most common causes are: bus wiring open or shorted; module without power or ground; module failed.
Related codes
- U0686Lost Communication With Catalyst Temperature Bank 2 Sensor 1
- U0685Lost Communication With Catalyst Temperature Bank 1 Sensor 2
- U0684Lost Communication With Catalyst Temperature Bank 1 Sensor 1
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.