U066A code meaning
Lost Communication With EGR Sensor E
Network system Generic code U06xx codes Check engine light
What U066A means
EGR sensors A to E are open slots in the code set: each maker decides whether a slot carries a valve position, a pressure or a differential pressure in the recirculation path. U066A means the engine controller no longer gets usable digital frames from the device it calls sensor E, typically a SENT part. No manufacturer documents this code publicly. In the published tables GM gives slot A to the high-pressure valve position and C to the low-pressure one, while Ford and GM use D for a SENT EGR pressure sensor (U0669); an E appears nowhere. CARB demands its own code when a digitally coded input goes silent. Analog faults of this slot are P2385 to P2389. Most systems then cut or limit EGR, and the EGR monitor stays incomplete.
U066A at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U066A
- Check engine light
- EGR switched off or limited, sometimes harsher combustion noise
- EGR readiness monitor not complete
Common causes of U066A
- Most likelySignal, supply or ground wire to EGR sensor E damaged by heat or chafing
- PossibleConnector at the sensor loose, corroded or contaminated with soot
- PossibleSensor electronics no longer transmitting
- Less likelyEngine controller input or software fault
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR sensor eVehicle bus wiring
What each part of U066A means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6A | The exact fault in that area. |
What to do next
- Note U066A 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 U066A
What does U066A mean?
U066A means "Lost Communication With EGR Sensor E". EGR sensors A to E are open slots in the code set: each maker decides whether a slot carries a valve position, a pressure or a differential pressure in the recirculation path. It is a generic code, so it means the same on every make.
Is it safe to drive with U066A?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U066A fail an emissions test?
Yes, it can. U066A is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U066A to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U066A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.