U0687 code meaning

What U0687 means

U0687 refers to the rear catalyst temperature probe of bank 2, the one behind the converter brick on the second cylinder row. Once its digital messages stop, the controller can no longer compare bank 2 inlet and outlet temperatures (P046B) and loses an over-temperature guard: such probes have long been used to warn when a converter runs hotter than it can tolerate, which on older two-way designs was around 750 °C. No manufacturer documents this code publicly, so MIL timing and debounce are not known; CARB only requires that silence of a digital input sets its own code. Analog faults at this point are P043A to P043D, and sensor 1 of the same bank is U0686. The car usually drives normally, but the fault should not be left, since misfires could go on overheating the converter.

U0687 at a glance

• Check engine lightYes, usually on
• Emissions testCan fail
• Limp modeNot expected
• Repair difficultyMedium, DIY possible
• Typical labor0.5 to 2.5 hours
• Clears after repairWhen cleared with a scanner

Symptoms of U0687

• Check engine light
• Bank 2 temperature comparison not possible
• No noticeable change in driving

Common causes of U0687

• Most likelyLead of the rear bank 2 probe damaged
• PossibleSensor electronics failed after overheating
• Less likelyConnector corroded

Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.

Parts involved

Catalyst temp sensor bank 2 sensor 2Vehicle bus wiring

What each part of U0687 means

What to do next

• Note U0687 and any other codes stored with it: several codes together often point to one cause.
• Check for loose connectors and damaged wiring around the parts the code names.
• Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
• Clear the code only after the repair. If it comes back, the fault is still there.

Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.

Codes often seen with U0687

• U0686 Lost Communication With Catalyst Temperature Bank 2 Sensor 1
• U0685 Lost Communication With Catalyst Temperature Bank 1 Sensor 2
• P043A Catalyst Temperature Sensor Circuit Bank 2 Sensor 2
• P043B Catalyst Temperature Sensor Circuit Range/Performance Bank 2 Sensor 2
• P043C Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 2
• P043D Catalyst Temperature Sensor Circuit High Bank 2 Sensor 2
• P046B Catalyst Temperature Sensor 1/2 Correlation Bank 2

Questions about U0687

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