U041B: Invalid Data Received From Exhaust Gas Sensor Module A

What it means

A control module received data from Exhaust Gas Sensor Module A that it judged invalid or implausible. This code identifies the rejected data, but does not by itself identify the cause.

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

Exhaust Gas Sensor Module A processes exhaust-sensor information and sends emissions-related data to other vehicle modules. U041B sets when a receiving module considers data from this A module invalid or implausible; it does not by itself identify a particular exhaust sensor or the cause.

Common causes

Most likely first.

1. Fault or implausible input at Exhaust Gas Sensor Module A
2. Damaged or loose network wiring or connector
3. Module power, ground, or programming issue

Symptoms

• Check-engine light may illuminate
• Emissions-control functions may be affected
• Other communication codes

How to diagnose it

1. Scan all modules and save freeze-frame and emissions data before clearing codes; check whether Exhaust Gas Sensor Module A has sensor, heater, power, or communication faults of its own.
2. Review live exhaust-sensor data reported through Module A, looking for missing, stuck, or contradictory readings under the conditions recorded in freeze-frame.
3. With the exhaust cool, inspect Module A's connectors and wiring near the exhaust for heat damage, chafing, corrosion, or loose connections.
4. Check related sensor and heater circuits using the vehicle wiring information and manufacturer's specification, since an input fault can make the module's transmitted data implausible.
5. If sensor inputs and wiring check out, test Module A's power, ground, and network circuits and check for applicable software updates.

Common fixes

• Repair heat-damaged or chafed wiring or secure a loose Module A connector.
• Repair the exhaust sensor or heater circuit identified by the module's codes and live data.
• Restore module power or ground if testing finds a fault.
• Update or replace Exhaust Gas Sensor Module A only after its inputs and circuits are verified.

Can I keep driving?

You can usually drive gently if the engine runs normally, but arrange diagnosis soon because emissions monitoring or control may be affected. Stop if the engine runs roughly, loses power, or the warning light flashes.