What it means
A control module received invalid data from particulate matter sensor B. The code identifies a data validity fault; the specific affected function depends on the vehicle.
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
Particulate matter sensor B reports soot-related measurements to vehicle modules that use them to manage exhaust emissions. U04B2 is set when a receiving module judges the data from sensor B invalid, even if communication is present; it does not by itself identify a failed sensor.
Common causes
Most likely first.
- Fault in the transmitting module or sensor
- Network wiring or connector fault
- Module power or ground fault
- Software or configuration issue
Symptoms
- An emissions or engine warning may appear
- Emissions control may be affected
How to diagnose it
- Record freeze-frame data and scan all modules for related communication or emissions codes to see whether the fault is isolated to sensor B.
- Check live data for particulate matter sensor B and note whether its readings are missing, implausible, or flagged invalid.
- Inspect sensor B's connector and nearby harness for loose pins, corrosion, heat damage, or chafing.
- Check the sensor and transmitting module's power and ground against the manufacturer's specification.
- Test the relevant network wiring and connector continuity, and check for shorts or poor connections using the vehicle wiring information.
- If wiring and supplies are sound, check for applicable software or configuration updates before condemning the sensor or a module.
Common fixes
- Reconnect or repair a loose or corroded sensor B connector.
- Repair damaged network wiring to the particulate matter sensor B or its transmitting module.
- Restore a faulty module power or ground connection.
- Apply the correct software or configuration update if one is available.
- Replace particulate matter sensor B or its transmitting module only after testing confirms the fault.
Can I keep driving?
If the vehicle runs normally and has no other warnings, a short, gentle drive may be possible, but avoid extended driving because emissions control may be impaired. Stop if engine behavior worsens or a warning indicates a more serious fault.
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.