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U0673 Lost Communication With Ion Sense Module

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

After each spark, a small bias voltage across the plug gap lets the ignition system measure the current carried by ions in the burning mixture; Ford's patent US20170030322A1 shows such an ion sensing module passing this signal to the controller for combustion and knock assessment. U0673 means the engine controller no longer hears from that module. Stellantis lists U0673-00 among the MIL codes in a series of powertrain controller reflash bulletins for the 3.0 L Hurricane twin-turbo six (sales codes EFC and EFH): 18-022-25 Rev. A for the 2025 Wagoneer and Grand Wagoneer, 18-106-25 for the 2026 Ram 1500 and 18-071-26 for the 2025 Ram 1500. The stated cause is controller software, so updating it comes before replacing hardware.

Likely causes

Powertrain controller software (Stellantis Hurricane engines)

Bus, supply or ground wiring of the ion sense module faulty

Ion sense module internally failed

Symptoms

Check engine light
Other stored codes from the same software issue
Usually no change in how the engine runs

Repair estimate

DifficultyEasyWorkshop job

Parts and labour€0–300

Time0.2–1.5 h

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

Parts involved

ion sense modulevehicle bus wiring

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, patents.google.com.