What it means
The vehicle bus reports loss of communication with smart EGR sensor E (position or flow). EGR closed-loop control loses its actual feedback.
At a glance
- Usually lights the warning light of the system that lost communication
- Affects emissions; the car can fail an emissions test
How it works
EGR sensor E supplies position or flow feedback that the engine controller uses to manage exhaust gas recirculation. U066A sets when the network stops delivering messages from sensor E, so EGR closed-loop control loses that sensor's information and emissions faults may result.
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 the engine and network modules, save freeze-frame data, and check for EGR or communication codes that identify whether sensor E is the only affected device.
- Review live data for EGR sensor E and compare its status with commanded EGR operation if both values are available.
- Inspect sensor E's connector and nearby harness for loose terminals, corrosion, heat damage, or abrasion.
- Verify sensor E's specified power and ground under load and check shared supplies shown in the wiring diagram.
- Test the network wires serving EGR sensor E for opens, shorts, and abnormal resistance using the manufacturer procedure.
- If power, ground, and bus wiring pass, perform the manufacturer's communication test for sensor E before considering replacement.
Common fixes
- Reconnect and secure the EGR sensor E connector.
- Repair damaged, heat-affected, or corroded wiring at sensor E.
- Restore a failed power or ground connection to the sensor.
- Repair an open or short in the network circuit to EGR sensor E.
- Replace EGR sensor E after its supply and network circuits test correctly.
Can I keep driving?
Driving may be possible if the engine behaves normally, but the lost EGR feedback can raise emissions and may lead to rough running or reduced performance. Limit driving if symptoms develop and have the fault diagnosed promptly.
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.