OBD-II code · Network
U05A9 NOx Sensor C Received Invalid Data From ECM/PCM
NOx sensor C (smart sensor with own ECU) received implausible data from the ECM/PCM. Engine load, fuel rate or temperature data needed for the sensor's internal compensation fails plausibility checks; the sensor reports degraded readings.
Is it safe to drive with U05A9?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyECM/PCM internal fault or sensor input drift
- PossibleSoftware version mismatch after replacement
- Less likelyGateway 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
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Nox Sensor C, Ecm
Related codes
- U05A1NOx Sensor A Received Invalid Data From ECM/PCM
- U05A2NOx Sensor B Received Invalid Data From ECM/PCM
- U05A6Invalid Data Received From Reductant Heater Control Module
- U05A7Invalid Data Received From Safety Integration Control Module
- U05A8Invalid Data Received From NOx Sensor C
- U05AAInvalid Data Received From Charge Air Cooler Coolant Pump
- U05ABInvalid Data Received From Engine Disconnect Clutch
- U05ACInvalid Data Received From Vehicle Thermal Management Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.