U02A4
Lost Communication With NH3 Sensor
U02A4 is an OBD-II diagnostic trouble code meaning: Lost Communication With NH3 Sensor. Common causes: open or short circuit in the nh3 sensor circuit, malfunction of the ammonia sensor itself. Estimated repair cost: $56–167.
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
Error U02A4 by Vehicle Brand
FAQ
What does the U02A4 code mean?
U02A4 is an OBD-II diagnostic trouble code that indicates: Lost Communication With NH3 Sensor
What causes a U02A4 error code?
The most common causes of U02A4 include: 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.
How do I fix a U02A4 diagnostic trouble code?
To fix U02A4: 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. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U02A4?
Limited driving only, diagnose soon
How much does it cost to fix U02A4?
The estimated repair cost for U02A4 is $56–167. Actual cost depends on your vehicle, location, and labor rates.
See also: Russian version · NationStat