U05A8: Invalid Data Received From NOx Sensor C

What it means

A receiving module detected implausible data from NOx sensor C (smart sensor with own ECU). NOx concentration or pumping current values fail plausibility checks and are rejected.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

NOx sensor C is a smart exhaust sensor with its own control unit that measures nitrogen oxides and may report pumping-current data used to assess the measurement. This code sets when a receiving module considers sensor C's NOx or pumping-current data implausible and rejects it, potentially triggering exhaust-system restrictions.

Common causes

Most likely first.

1. Module internal fault or sensor input drift
2. Software version mismatch after replacement
3. Gateway module routing CAN messages incorrectly

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

1. Save freeze-frame data and scan all modules for NOx sensor C, SCR, and communication codes to establish when the invalid report occurred.
2. Check live NOx sensor C concentration and pumping-current data alongside exhaust operating conditions, and compare with other available exhaust sensor readings.
3. Inspect sensor C's connector, hot-zone harness, sensor control unit connections, and CAN wiring for heat damage, corrosion, loose pins, or poor grounds.
4. Check for related exhaust temperature, SCR, or power-supply faults that could make sensor C's readings implausible.
5. Verify that NOx sensor C and the receiving module or gateway have compatible software and configuration, especially after replacement.
6. If wiring and related inputs are sound, use manufacturer-approved network tests to determine whether sensor C, the receiving module, or gateway is at fault.

Common fixes

• Repair damaged, heat-affected, or corroded sensor C wiring and connectors.
• Fix related exhaust temperature, SCR, power, or ground faults affecting the validity of sensor C data.
• Load compatible software or configuration for NOx sensor C or a replaced module.
• Replace NOx sensor C or a confirmed faulty gateway or receiving module.

Can I keep driving?

Avoid extended or heavy-load driving because invalid NOx data can compromise emissions control and may lead to limp mode or power restrictions. If the vehicle is already in limp mode or shows a serious exhaust warning, stop in a safe place and arrange diagnosis.