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DTC codes / U06xx · Network communication / U0680

U0680Lost Communication With Barometric Pressure Sensor B

U0680 is a generic network communication code indicating that a control module on the vehicle's Controller Area Network (CAN) bus has lost contact with the Barometric Pressure Sensor B, which is often integrated into the Engine Control Module (ECM) or Powertrain Control Module (PCM). The computer detected that expected serial data messages from that sensor or its dedicated module have stopped arriving within the required time window, so it flags the missing signal as a communication fault rather than a direct sensor performance error.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaNetwork communication

Symptoms you may notice

  • The check engine light or service vehicle soon message illuminates, often with no other noticeable symptoms.
  • The engine may run rich or have a rough idle because the ECM is substituting a default barometric pressure value.
  • Reduced fuel economy or black exhaust smoke may appear if the default pressure value is significantly off from actual altitude.
  • A stored U0680 code may be accompanied by other communication codes such as U0100 or U0155 if the entire bus is affected.
  • In some vehicles, the engine may enter a limp-home mode with limited power or forced high idle.
  • Intermittent driveability issues that correlate with temperature changes or rough road surfaces, pointing to a wiring fault.

Common causes, most likely first

  1. A faulty barometric pressure sensor B, especially when the sensor is a separate module that has failed internally.
  2. Damaged, corroded, or disconnected wiring or connectors in the circuit between the sensor and the ECM or PCM.
  3. A blown fuse or poor ground connection that supplies power or ground to the barometric pressure sensor circuit.
  4. A software or calibration issue in the ECM or PCM that causes it to stop polling the sensor correctly.
  5. A failed ECM or PCM that is unable to process or request the sensor data over the network.
  6. CAN bus wiring faults, such as a short to ground or voltage, that disrupt messages from the sensor module.
  7. Aftermarket electrical accessories or poor previous repairs that introduce interference or incorrect voltage on the sensor circuit.

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes, freeze-frame data, and live barometric pressure readings to confirm the sensor signal is missing or erratic.
  2. Inspect the barometric pressure sensor B and its connector for physical damage, corrosion, or loose pins, and check the sensor reference voltage and ground with a multimeter.
  3. Check all fuses and relays that supply power to the sensor circuit, and verify battery voltage and ground integrity at the sensor connector.
  4. Perform a wiggle test on the wiring harness between the sensor and the ECM while watching live data to expose intermittent opens or shorts.
  5. If the sensor is a separate serviceable unit, substitute it with a known-good sensor and clear the code to see if communication returns.
  6. Check for technical service bulletins or software updates for the ECM or PCM that address communication faults with the barometric pressure sensor.
  7. If all wiring and the sensor test good, diagnose the CAN bus with an oscilloscope and, as a last resort, test or replace the ECM or PCM after confirming power and ground to the module.

Why barometric sensor codes mislead

  • Many vehicles integrate the barometric pressure sensor into the ECM or PCM, so U0680 often points to an internal ECM communication fault rather than a standalone sensor that can be unbolted and replaced.
  • A missing barometric pressure signal does not always cause a noticeable driveability problem because the ECM substitutes a default value based on throttle position and mass airflow sensor readings, so the code may be the only clue.
  • Technicians sometimes replace the barometric sensor only to find the real fault is a chafed wire in the harness near the engine mount or a corroded ground that also affects other sensors on the same circuit.
  • U0680 can be set by a low battery or a recent jump-start that caused a momentary voltage drop on the network, so always clear the code and verify it returns before condemning any part.
  • On vehicles with a separate barometric pressure sensor module, a failed sensor can pull down the shared reference voltage and set communication codes for other sensors on the same bus, leading to a misdiagnosis of the ECM.

Can I keep driving with U0680?

You can usually continue driving to a repair shop because the ECM substitutes a default barometric pressure value, but avoid heavy towing or sustained high-speed driving until the fault is repaired. If the engine runs poorly, stalls, or enters limp mode, stop driving and have the vehicle towed to prevent damage or unsafe operation.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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