Lost Communication with Telephone Control Module
The U0197 code indicates that the main control module (typically the gateway or BCM) has lost serial communication with the Telephone Control Module over the vehicle's data bus (CAN, LIN, or other network protocol). This means the telephone module is not transmitting status or response messages within the defined timeout period, disabling hands-free functions, contacts, and Bluetooth audio.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty or internally damaged Telephone Control Module (TCM)
- Open circuit, short to ground, or short to battery on the communication bus (CAN High/Low or LIN) to the telephone module
- Loose, corroded, or backed-out terminals in the telephone module connector
- Loss of power (B+) or ground to the telephone module (blown fuse, faulty relay, wiring issue)
- Software configuration error or version incompatibility after an update or programming
- Damaged or missing bus termination resistor on the affected network
3. Symptoms You Will Notice
- Hands-free calling and Bluetooth audio not working
- Phone contacts not syncing with the vehicle
- Telephone module unresponsive or not detected by scan tool
4. Step-by-Step Diagnosis
Scan all modules for related communication codes and check for U0197 in the gateway or BCM
Inspect the telephone module connector for corrosion, loose pins, or damage
Test power and ground circuits at the telephone module (B+ and ground)
Check the communication bus (CAN/LIN) wiring for opens, shorts, or high resistance
Verify bus termination resistance (typically 60 ohms on CAN) at the module or network
If wiring and power are OK, attempt to reprogram or replace the telephone module
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive. The vehicle will operate normally, but hands-free calling and Bluetooth audio will be disabled.
How much does it cost to fix?▼
Diagnosis typically costs $100-$150. Repair costs vary: a blown fuse or wiring repair may be under $200, while replacing the telephone module can range from $400 to $800 including labor.