OBD-II code · Network
U02A1 Lost Communication With NOx Sensor C
The vehicle bus reports loss of communication with NOx sensor C (smart sensor with own ECU). The SCR catalyst control loop loses its actual NOx feedback and may switch to substitute values.
Is it safe to drive with U02A1?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyBus wiring open or shorted
- PossibleModule without power or ground
- PossibleModule failed
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
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–3 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Nox Sensor C, Vehicle Bus Wiring
Related codes
- U029DLost Communication With NOx Sensor A
- U029ELost Communication With NOx Sensor B
- U029FLost Communication With Evaporative Emission System Leak Detection Control Module
- U02A0Invalid Data Received From Hybrid/EV Battery Interface Control Module D
- U02A2Lost Communication With Reductant Quality Module
- U02A3Lost Communication With Particulate Matter Sensor
- U02A4Lost Communication With NH3 Sensor
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.