U02A4

Lost Communication With NH3 Sensor

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$56–167 (est.)

Symptoms

Check Engine Light Is On
Reduced engine power
Increased urea consumption (AdBlue)
Increased level of harmful emissions
Possible problems starting the engine

Causes

Open or short circuit in the NH3 sensor circuit
Malfunction of the ammonia sensor itself
Problems with the sensor connector (oxidation, damage)
SCR ECU malfunction
Sensor power problems

How to Fix

Check the integrity of the wiring to the NH3 sensor
Inspect the sensor connector for damage
Check the power supply and ground of the sensor
Test or replace NH3 sensor
If necessary, check or reflash the SCR system ECU

Related codes

U02A2 U02A3 U02A5