What it means
A control module is not receiving expected messages from the Telematic Control Module. Telematic functions may be unavailable; the code alone does not identify why communication was lost.
How it works
The Telematic Control Module handles connected vehicle services and communicates with other modules over the vehicle network; some vehicles also use a backup battery to keep it available. U0198 sets when the reporting module stops receiving the telematics module's expected messages within its timeout.
Common causes
Most likely first.
- TCU unpowered or backup battery dead
- Mobile antenna disconnected
- Gateway module routing CAN messages incorrectly
Symptoms
- Telematic functions may be unavailable
- Other communication codes
How to diagnose it
- Scan all modules and record freeze-frame data and related codes to see whether only the telematics module is offline or the vehicle has a broader network or voltage issue.
- Check battery condition and system voltage, then verify the telematics module's main power and ground.
- Inspect the module's network connector and mobile antenna connection for looseness, corrosion, or damage.
- If equipped, check the telematics backup battery and its connections according to the vehicle's service information.
- Check the CAN wiring and gateway message status for the telematics module, comparing circuit measurements with the manufacturer's specification.
Common fixes
- Repair a loose or corroded telematics module connector or ground.
- Reconnect or repair a damaged mobile antenna lead if telematics service is also affected.
- Replace a failed backup battery if vehicle-specific testing confirms it is faulty.
- Repair CAN wiring or gateway routing faults confirmed by diagnostics.
- Replace or reprogram the telematics control module if its power, network, and antenna checks pass but it remains offline.
Can I keep driving?
Connected services such as remote features or automatic assistance may be unavailable, while driving is generally unaffected by this code alone. If the vehicle relies on telematics for emergency assistance, do not assume that service is working until communication returns.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.