U0668 code meaning
Lost Communication With Engine Oil Level Sensor Circuit
What U0668 means
Despite the word circuit in its name, U0668 concerns the data link to the oil level sensor, not a voltage fault. Sensors in the sump measure the oil height either thermally or by ultrasound; Hella's PULS type packs an ultrasonic transducer, a temperature sensor and an ASIC into one module that sends its result to the engine controller over a single signal line, and loss of supply or ground is one listed failure cause. When that signal no longer arrives or is unreadable, a separate lost-communication code can be stored. No manufacturer documents U0668 in public. Because oil level is normally not emission-relevant, CARB's rule on separate codes for silent digital inputs hardly applies. Electrical sensor faults are P250A to P250E, low or high oil P250F and P252F. Check the dipstick until fixed.
U0668 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0668
- Oil level warning or service message in the display
- Oil level reading unavailable
Common causes of U0668
- Most likelyMissing supply voltage or ground at the sensor
- PossibleSensor electronics failed or oil inside the housing
- PossibleCorroded or damaged connector or harness at the oil pan
- Less likelyReceiving control unit input faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine oil level sensorVehicle bus wiring
What each part of U0668 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 68 | The exact fault in that area. |
What to do next
- Note U0668 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.
Questions about U0668
What does U0668 mean?
U0668 means "Lost Communication With Engine Oil Level Sensor Circuit". Despite the word circuit in its name, U0668 concerns the data link to the oil level sensor, not a voltage fault. It is a generic code, so it means the same on every make.
Is it safe to drive with U0668?
U0668 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0668 fail an emissions test?
U0668 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0668 to fix?
Difficulty: easy. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U0668 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.