U0197
Lost Communication With Telephone Control Module
- Severity
- Medium
- Driving
- Drivable — book it in
The control module has stopped receiving messages from the telephone control module. Hands-free calling, connected services and remote app functions will not work. On a vehicle fitted with automatic crash notification - eCall in Europe, and its equivalents elsewhere - this is also the module that calls for help automatically after a serious collision, and that will not happen while this fault is present.
Possible causes
- CommonLow battery voltage or a discharged battery, dropping modules off the bus
- CommonBlown fuse or corroded earth on the supply to the telephone control module
- PossibleCorroded or water-ingressed connector
- PossibleDamaged, chafed or corroded bus wiring
- PossibleFailed module
- PossibleModule backup battery flat or expired
- PossibleNetwork service withdrawn - older modules on retired mobile networks stop working permanently
What you might notice
- Hands-free calling unavailable
- Connected or app-based services not working
- Emergency call warning light or message
- Vehicle reports no network
- No effect on how the car drives
What to check, in order
- Do not assume automatic crash notification is working. If the vehicle has an emergency call button and it shows a fault, treat that as the important part of this code and carry a phone.
- Check battery voltage and state of charge before anything else. A weak or failing battery drops modules off the bus and sets lost-communication codes with no wiring fault at all - this is the single most common false lead in this whole family.
- Check the fuses, earths and connector for the telephone control module.
- Consider the vehicle's age. Telematics modules built for 2G or 3G networks stopped working when those networks were switched off, and no repair brings them back - the module is fine, the network is gone.
- Check whether the module has its own backup battery. These expire and are a common cause of emergency call faults.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
U00xxU01xxU02xxU03xxU04xxU05xxU06xxU07xxU08xxU09xxU0AxxU0BxxU0CxxU0DxxU0ExxU0FxxU10xxU11xxU12xxU13xxU14xxU15xxU16xxU17xxU18xxU19xxU1AxxU1BxxU1CxxU1DxxU1ExxU1FxxU20xxU21xxU22xxU23xxU24xxU25xxU26xxU27xxU28xxU29xxU2AxxU2BxxU2CxxU2DxxU2ExxU2FxxU30xxU31xxU32xxU33xxU34xxU35xxU36xxU37xxU38xxU39xxU3AxxU3BxxU3CxxU3DxxU3ExxU3Fxx
Network communication
U0100U0101U0102U0103U0104U0105U0106U0107U0108U0109U0110U0111U0112U0113U0114U0115U0116U0117U0118U0119U0120U0121U0122U0123U0124U0125U0126U0127U0128U0129U0130U0131U0132U0133U0134U0135U0136U0137U0138U0139U0140U0141U0142U0143U0144U0145U0146U0147U0148U0149U0150U0151U0152U0153U0154U0155U0156U0157U0158U0159U0160U0161U0162U0163U0164U0165U0166U0167U0168U0169U0170U0171U0172U0173U0174U0175U0176U0177U0178U0179U0180U0181U0182U0183U0184U0185U0186U0187U0188U0189U0190U0191U0192U0193U0194U0195U0196U0197U0198U0199