Network, generic

U0619 Lost Communication With Reductant Level Sensor A

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

Reductant level sensor A reports how much diesel exhaust fluid (DEF, AdBlue) is left in the SCR tank. Newer tank units are smart sensors: a sensing element plus electronics that transmit level, temperature and often concentration as digital frames over CAN, SENT or LIN. U0619 means the engine or aftertreatment controller gets no valid frames from that level sensor, whether the line is silent, frames time out, checksums fail or the sensor flags an internal fault. CARB requires a digital input that stops talking to store its own code, apart from the circuit and plausibility codes P203A to P203E. No manufacturer publicly documents a detection rule for U0619. Without a level value the low-DEF warning is lost and the controller can no longer rule out an empty tank, which California treats as an SCR fault.

Likely causes

Corroded, water-soaked or loose connector at the DEF tank sensor

Data line, supply or ground of the tank sensor chafed or broken along the frame

Electronics of the tank level sensor failed (often replaced as a tank sender unit)

Controller software or configuration not matching the installed sensor

Symptoms

Check engine light or SCR warning
DEF gauge blank or frozen at a fixed value
No warning before the DEF tank runs empty

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€80–1,200

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant level sensor asensor wiring

References: law.cornell.edu, static.nhtsa.gov, ssi-sensors.com.