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DTC codes / U06xx · Network communication / U0667

U0667Lost Communication With Engine Oil Temperature Sensor A

U0667 is a network communication code indicating that a control module on the vehicle's Controller Area Network (CAN) bus has lost contact with the Engine Oil Temperature Sensor A circuit, typically because the module responsible for reporting that sensor's data is no longer transmitting. The computer did not detect an electrical fault in the sensor itself; it detected the absence of a valid CAN message carrying oil temperature information from the originating module.

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

Symptoms you may notice

  • Illumination of the check engine light or a dedicated communication fault indicator on the dashboard.
  • Often no symptoms besides the warning light, especially if the vehicle uses a substitute temperature value for engine protection.
  • Erratic or missing engine oil temperature readings on a dashboard display or scan tool live data stream.
  • Reduced engine power or limp-home mode if the powertrain control module substitutes a default oil temperature and limits load.
  • Intermittent warning light activation that correlates with rough road surfaces, wet weather, or temperature extremes.
  • Other unrelated warning lights or module communication codes appearing simultaneously if the fault lies on a shared CAN bus segment.

Common causes, most likely first

  1. A failed or intermittently failing engine oil temperature sensor that stops reporting data to its host module.
  2. Damaged, chafed, or corroded wiring between the oil temperature sensor and the module that publishes its data on the CAN bus.
  3. A faulty module that reads the oil temperature sensor and relays it over CAN, such as the engine control module or a body/instrument cluster module depending on architecture.
  4. Loose or corroded CAN bus connector pins at any module on the affected network segment, interrupting the message.
  5. A software or calibration issue in a module that causes it to stop broadcasting oil temperature messages under certain conditions.
  6. Voltage supply or ground problems at the module that hosts the oil temperature sensor, causing that module to drop offline.
  7. Aftermarket electronic accessories wired into the CAN bus or sensor circuit that introduce interference or incorrect resistance.

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes across every module, then verify that live engine oil temperature data is missing or implausible in the module that should report it.
  2. Inspect the engine oil temperature sensor connector and the module connector for corrosion, pushed pins, or loose terminals, and repair as needed.
  3. Perform a resistance and voltage-drop test on the sensor signal and ground circuits between the sensor and its host module, comparing to manufacturer specifications.
  4. Check CAN bus integrity with a digital multimeter or oscilloscope at the diagnostic link connector, looking for correct differential voltage and no shorts to ground or battery voltage.
  5. If the sensor and wiring test good, substitute a known-good sensor or simulate the signal to confirm whether the host module begins broadcasting oil temperature again.
  6. Update or reflash the host module software if a known calibration issue exists, following the manufacturer's programming procedure.
  7. Clear codes and perform a road test with live data monitoring to confirm that oil temperature messages are present and the code does not return.

What the oil temperature message really means

  • U0667 is a communication code, not a sensor circuit code, so replacing the oil temperature sensor without checking the CAN bus and host module often fails to fix the problem.
  • Some vehicles broadcast oil temperature only under specific conditions, such as after a cold start or above a certain engine speed, so a missing message during a quick scan can be a false alarm.
  • A weak or failing battery or charging system can cause modules to drop offline intermittently, setting U0667 along with other communication codes that clear after a proper voltage restore.
  • Aftermarket remote starters, alarms, or piggyback tuners spliced into CAN wiring are a commonly overlooked cause of intermittent lost communication with sensor data.
  • The module that publishes oil temperature may not be the engine control module; on some architectures it is the instrument cluster or a body control module, so always check the network topology before condemning parts.

Can I keep driving with U0667?

The vehicle is generally safe to drive short distances because the powertrain control module usually substitutes a default oil temperature, but avoid sustained high-load driving, towing, or track use until the fault is repaired. If the warning light is accompanied by reduced power or multiple communication codes, have the vehicle inspected promptly.

Tools that help

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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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