U0673 code meaning
Lost Communication With Ion Sense Module
Network system Generic code U06xx codes Check engine light
What U0673 means
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.
U0673 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy
- Typical labor0.2 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0673
- Check engine light
- Other stored codes from the same software issue
- Usually no change in how the engine runs
Common causes of U0673
- Most likelyPowertrain controller software (Stellantis Hurricane engines)
- PossibleBus, supply or ground wiring of the ion sense module faulty
- Less likelyIon sense module internally failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ion sense moduleVehicle bus wiring
What each part of U0673 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 73 | The exact fault in that area. |
What to do next
- Note U0673 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0673
What does U0673 mean?
U0673 means "Lost Communication With Ion Sense Module". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U0673?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U0673 fail an emissions test?
Yes, it can. U0673 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0673 to fix?
Difficulty: easy. A typical repair takes 0.2 to 1.5 hours of work. This is a job for a workshop.
Will U0673 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.