What it means
The vehicle bus reports loss of communication with smart engine oil level sensor. Oil-level warnings cannot be issued reliably; refill alerts may be missing.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The engine oil level sensor reports the amount of oil in the engine to the vehicle network so the vehicle can provide level warnings. U0668 sets when messages from this sensor are lost, making low-oil alerts or refill reminders unreliable.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- 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
- Scan all modules and review freeze-frame data for oil-level or network codes that could identify a shared electrical problem.
- Check the oil level manually on level ground using the vehicle's stated checking procedure, then compare it with any available live sensor status.
- Inspect the oil level sensor connector and harness for oil intrusion, corrosion, loose terminals, or damage near the sump.
- Check the sensor's specified power and ground, including under load, against the wiring diagram.
- Test the network circuit to the oil level sensor for opens, shorts, or abnormal resistance using the manufacturer procedure.
- If the circuit tests pass, follow the manufacturer's sensor communication test before replacing the oil level sensor.
Common fixes
- Reconnect and secure the oil level sensor connector.
- Repair oil-soaked or damaged wiring and corroded terminals.
- Restore a failed sensor power or ground connection.
- Repair an open or short in the sensor network wiring.
- Replace the oil level sensor after its power, ground, and network circuit pass testing.
Can I keep driving?
Driving is generally possible if the oil level is checked manually and is correct, but do not rely on the vehicle's low-oil warning while this fault is present. Stop and check the oil if an oil-pressure warning appears, since that warning can indicate an urgent lubrication problem.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.