Network
generic / SAE
U02A4
Lost Communication With NH3 Sensor
The vehicle bus reports loss of communication with the ammonia (NH3) slip sensor downstream of the SCR. Detection of urea over-dosing is impaired.
SystemNetwork
Typegeneric / SAE
GroupU0
Range / number2 / A4
Possible causes
- Bus wiring open or shorted high
- Module without power or ground medium
- Module failed medium
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
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 300–1500 €
- Estimated time: 0.5–3 h
- Component: nh3 sensor
- Component: vehicle bus wiring
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012