What it means
The vehicle bus reports loss of communication with the particulate matter (PM) sensor (smart sensor with own ECU). DPF post-cat soot monitoring loses its primary feedback signal.
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
The particulate matter sensor is a smart sensor with its own control electronics that reports soot measurements after the diesel particulate filter. U02A3 sets when the vehicle network stops receiving the sensor's messages, leaving the engine controller without its main post-filter soot feedback.
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 save freeze-frame data to determine whether the PM sensor communication loss coincided with other network faults or low system voltage.
- Check live DPF and PM sensor data for a missing sensor status or soot reading while confirming other network devices are communicating.
- Inspect the PM sensor connector and harness along the exhaust for heat damage, chafing, corrosion, or a loose connection.
- Check the sensor's power and ground using the manufacturer's wiring information and test conditions.
- Test the PM sensor network wires for an open, short, or poor connection using the manufacturer's procedure.
- If wiring and supplies pass, verify the PM sensor itself is not the source of the missing messages before replacing it.
Common fixes
- Reconnect or repair a loose or corroded PM sensor connector.
- Repair heat-damaged or chafed wiring at the exhaust-mounted sensor.
- Repair an open or short in the sensor's network circuit.
- Restore the sensor's power or ground supply.
- Replace the PM sensor if its wiring and supplies pass testing.
Can I keep driving?
You can often drive cautiously if the vehicle has no reduced-power warning, but post-filter soot monitoring and emissions diagnostics are impaired. Avoid prolonged use, especially if a DPF warning or reduced-power condition develops.
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.