OBD-II trouble code
U041B: Invalid Data Received From Exhaust Gas Sensor Module
A module is receiving messages from the exhaust gas sensor module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $900
- DIY difficulty
- Shop recommended
What does U041B mean?
Some vehicles use a dedicated exhaust gas sensor module — a smart controller that conditions and digitizes the signals from exhaust sensors such as wideband air/fuel (oxygen) sensors, NOx sensors, or exhaust temperature sensors — and reports those readings to the engine control module over the network instead of running each sensor as a simple analog wire. U041B sets when a receiving module is still hearing from that exhaust gas sensor module, but the data in its messages is invalid: a value is out of range, implausible, or contradicts what other modules see. The link is alive; the content can't be trusted. That is the crucial difference from a lost-communication code, which means the module has gone completely silent.
Because the fault is bad data rather than a dead bus, the causes cluster around whatever makes the module broadcast wrong information. A failing exhaust sensor feeding the module — a degraded wideband oxygen sensor, an aging NOx sensor, or an exhaust temperature sensor reading out of range — can push the module into reporting values other modules reject. Low system voltage is a classic trigger, since the heater circuits in exhaust sensors draw meaningful current and module logic gets unreliable as voltage sags. Corroded or heat-damaged connectors are common because these sensors and their module live in one of the hottest, most vibration-heavy areas of the vehicle. The module's own software can be at fault if it is outdated, corrupted, or was never properly programmed after a replacement.
Symptoms depend on which reading is invalid. You may see a check engine light, an emissions-readiness monitor that will not complete, or fuel-trim and driveability oddities if the engine control module is being fed questionable air/fuel data. On diesels, a bad NOx reading can feed into SCR dosing strategy and emissions inducement. The vehicle usually remains driveable, but U041B is frequently a secondary code — read the full list, because a companion oxygen-sensor, NOx-sensor, or exhaust-temperature code often names the real root cause.
Common causes
- Failing wideband oxygen, NOx, or exhaust temperature sensor feeding the module bad data
- Low system voltage or a weak battery/charging system
- Corroded, melted, or heat-damaged connectors near the exhaust
- Chafed or broken wiring between the sensors and the module
- Outdated, corrupted, or mismatched exhaust gas sensor module software
- Module replaced without proper programming
- Electrical noise or damaged bus wiring corrupting messages in transit
- Exhaust gas sensor module internal fault
Symptoms
- Check engine light illuminated
- Emissions readiness monitors will not complete
- Fuel-trim drift, hesitation, or minor driveability issues
- On diesels, possible SCR/NOx-related warnings
- Companion oxygen, NOx, or exhaust temperature codes stored alongside U041B
- Vehicle generally still driveable
Diagnostic steps
- 1.Read ALL stored codes first — U041B is often secondary to an oxygen, NOx, or exhaust temperature code that names the bad signal.
- 2.Check battery and charging system voltage; low voltage is a common cause of implausible module data.
- 3.Inspect exhaust sensor connectors and wiring for corrosion, melting, and heat/vibration damage.
- 4.Use live data to compare the module's reported sensor values against expected readings and other modules.
- 5.Verify the module has the correct, current calibration, especially if it or a related sensor was recently replaced or flashed.
- 6.Address any companion sensor codes before condemning the module itself; the underlying fault often clears U041B.
Repair cost
$100 – $900
Cost depends on what is producing the bad data. Replacing a wideband oxygen sensor typically runs $150-$450 installed; a NOx sensor is pricier at $300-$700. Correcting low voltage or a charging fault is $150-$600, and repairing corroded exhaust-area wiring varies with access. A module reflash is usually $100-$300, and module replacement with programming is the expensive case — but that should only follow thorough diagnosis, since U041B is frequently a secondary code.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.