U0667: Lost Communication With Engine Oil Temperature Sensor A

What it means

The vehicle bus reports loss of communication with smart engine oil temperature sensor A. Oil-life model and oil-protection logic switch to a substitute value.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

Engine oil temperature sensor A sends oil-temperature data over the vehicle network for oil-life calculations and oil-protection strategies. U0667 sets when the module stops receiving messages from sensor A, so those functions may use a substitute value rather than the measured oil temperature.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

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

How to diagnose it

1. Scan all modules and save freeze-frame data, noting any oil-temperature, oil-life, or network codes that appear with U0667.
2. Review live data for engine oil temperature sensor A and compare it with other temperature readings after a cold soak and as the engine warms.
3. Inspect sensor A's connector and harness for loose terminals, oil contamination, corrosion, heat damage, or chafing.
4. Check the sensor's specified power and ground under load using the vehicle wiring diagram.
5. Test the network wiring to sensor A for opens, shorts, or abnormal resistance according to the manufacturer procedure.
6. If the power, ground, and bus circuit pass, use the manufacturer's communication test to confirm whether oil temperature sensor A has failed.

Common fixes

• Reconnect and secure engine oil temperature sensor A's connector.
• Repair oil-contaminated, heat-damaged, or corroded wiring at sensor A.
• Restore the sensor's failed power or ground connection.
• Repair an open or short in the network circuit to sensor A.
• Replace engine oil temperature sensor A after its supply and network circuits pass testing.

Can I keep driving?

Driving is generally possible if there are no oil-pressure or overheating warnings, but oil-temperature protection and oil-life calculations may be less reliable. Avoid sustained heavy loads until the sensor communication fault is repaired, and stop if an oil-pressure warning appears.