P3071 OBD Code Definition:
Reservoir for Additive for Particulate Filter Empty
P3071 OBD Code Description:

Possible Symptoms

• Malfunction Indicator Light (MIL) active
• Particle Filter Regeneration not working

Possible Causes

• Additive Reservoir empty
• Additive Level Sensor (G504) faulty

Possible Solutions

• Check Additive Level, Refill Additive Reservoir
• Check Engine (01) Measuring Value Blocks (MVB) 072.3
• Check Additive Level Sensor (G504)