Invalid Data from Exhaust Gas Sensor Module
The U041B code indicates that the engine control module (ECM/PCM) has received invalid data from the Exhaust Gas Sensor Module (typically associated with a NOx sensor or smart wideband oxygen sensor) over the CAN communication bus. The message was received, but its content failed integrity validation—such as checksum errors, rolling counter mismatches, or out-of-range data—or the message format was incorrect.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty exhaust gas sensor module (NOx sensor or smart O2 sensor) with internal failure
- Damaged wiring or connectors (open, short, corrosion) on the CAN bus to the sensor
- CAN bus communication errors (electrical noise, incorrect termination)
- Internal ECM/PCM failure in message reception or validation
- Outdated or corrupted software in the ECM/PCM or sensor
3. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or fuel economy
4. Step-by-Step Diagnosis
Scan for additional codes and verify U041B is present
Inspect exhaust gas sensor module wiring and connectors for damage or corrosion
Check CAN bus integrity (termination, voltage levels, noise) with an oscilloscope
Test the exhaust gas sensor module per manufacturer procedures
Update ECM/PCM and sensor software to latest version if applicable
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but the vehicle may experience reduced performance or fuel economy. Have it diagnosed soon to prevent further issues.
How much does it cost to fix?▼
Typically $200–$800, depending on whether the sensor ($150–$500) or ECM ($500–$1500) needs replacement, plus labor.