DTC codes / U02xx · Lost communication with a control module / U02A2
U02A2 means the engine control module has lost the controller area network communication link with the reductant quality module, which is the sensor module that measures the quality of diesel exhaust fluid (DEF) on selective catalytic reduction systems. The computer sets this code when it stops receiving the module's periodic status messages over the network, not when it detects poor fluid quality itself.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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