U0198
Lost Communication with Telematic Control Module
The vehicle has lost the telematics module (eCall / Connected Services / TCU). Emergency call, remote services and over-the-air features are unavailable until the module is back online.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
Ordered by how often each turns out to be the cause.
- TCU unpowered or backup battery deadCommon
- Mobile antenna disconnectedLess likely
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- Telematics Module
- CAN Bus Wiring
U0198 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.