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U040F Invalid Data Received From Reductant Control Module

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

On a diesel with SCR, the reductant control module looks after the urea circuit, chiefly the pump, dosing and heater control, and reports pressure and status to the engine controller. U040F means its messages arrive but fail validation. GM's 2025 ECM tables check counter and checksum of the DEF information and dosing status frames, count 6 errors among 15 or 3 among 10 checks as a failure; the result is Type A with the MIL on trip one. Ford's 2023 diesel OBD summary groups U040F with the functional test of the reductant pump motor and sets it when the duty-cycle control signal of the pump motor controller leaves the 4 to 96 percent window, next to pump speed, voltage and temperature codes. Without trusted module data dosing is stopped, NOx rises and the inducement strategy may later limit speed. U010E is lost contact.

Likely causes

Pump motor controller in the reductant module reporting an invalid control signal
Corroded connector or damaged bus line at the tank-mounted module
Software of the reductant module or ECM out of step
Reductant control module internally faulty

Symptoms

  • Check engine light
  • DEF/AdBlue warning with countdown to a speed limit
  • Further SCR or reductant pump codes stored

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–3 h

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

Parts involved

reductant control module

Related codes

U010EU030FU05A3U05A6

References: gsi.ext.gm.com, fordservicecontent.com, law.cornell.edu.