U0157 is a generic OBD-II network communication diagnostic trouble code indicating that communication with the Telematics Control Module (TCM) has been lost. Depending on the vehicle, the telematics module may manage cellular communication, emergency assistance, vehicle tracking, remote services, connected-car functions, or communication with external networks.
The exact module name, location, network architecture, wiring, and functions vary by manufacturer, model, and model year. Always use vehicle-specific service information for final diagnosis.
U0157 Code Details
Code: U0157
Meaning: Lost Communication With Telematics Control Module
Type: Generic OBD-II Network Communication Code
Main System: Telematics / Vehicle Communication Network
Symptoms of U0157
- Connected-car or telematics functions may stop working.
- Emergency assistance functions may become unavailable.
- Remote vehicle services may not respond.
- Vehicle tracking or communication services may be interrupted.
- Telematics-related warning messages may appear.
- Multiple communication-related DTCs may be stored.
- Scan tool may be unable to communicate with the telematics module.
- Intermittent network or communication problems.
Common Causes of U0157
- Low battery voltage.
- Blown fuse supplying the telematics module.
- Missing module power supply.
- Poor or damaged module ground.
- Open CAN High or CAN Low circuit.
- Shorted or damaged communication wiring.
- Loose or corroded electrical connector.
- Water intrusion.
- Damaged wiring or terminals.
- Another control module interfering with the vehicle network.
- Internal failure of the telematics control module.
- Incorrect programming or configuration after module replacement.
How Serious Is U0157?
U0157 is generally a moderate communication fault, but its importance depends on the functions provided by the telematics system. Loss of communication can disable connected-car, emergency-assistance, remote-control, or tracking functions.
If the vehicle's emergency communication or other safety-related telematics functions are unavailable, the problem should be repaired promptly.
Can You Drive With U0157?
The vehicle will often continue to start and drive normally because the telematics module is not normally responsible for basic engine operation. However, connected services and some emergency or communication features may not function while the fault is active.
How to Diagnose U0157
1. Scan All Control Modules
Perform a complete vehicle scan and record U0157 together with any other communication, body, power, or network codes. Determine whether the telematics module is the only module that has stopped communicating.
2. Check Battery and Charging Voltage
Verify battery condition and charging-system voltage. Low voltage during starting can cause the telematics module or other network modules to reset or temporarily go offline.
3. Check Telematics Module Fuses
Use the vehicle-specific fuse diagram to identify all power supplies for the telematics module. If a fuse is blown, determine the cause before replacing it.
4. Test Power and Ground
Verify battery and ignition feeds and test the module ground according to manufacturer specifications. A missing power or ground supply can make a functional module appear to have failed.
5. Inspect Connectors and Wiring
Inspect the telematics module connector for corrosion, loose terminals, bent pins, water contamination, damaged locks, or poor terminal tension. Check the harness for chafing, cuts, or previous repairs.
6. Check CAN Communication
Inspect CAN High and CAN Low circuits for opens, shorts, damaged wiring, or poor connections. Follow the manufacturer's wiring diagram because the telematics module may communicate through a specific CAN network or gateway.
7. Check Whether Another Module Is Affecting the Network
If multiple control modules report communication failures, investigate common network circuits and other modules before replacing the telematics unit.
8. Test the Telematics Control Module
If power, ground, connectors, and communication circuits are verified, follow the manufacturer's procedure to determine whether the telematics module has an internal fault or requires programming.
U0157 Oscilloscope Signal Patterns
An oscilloscope can be useful when U0157 is caused by an intermittent, noisy, or distorted CAN communication signal. It is especially useful when conventional voltage and continuity tests do not reproduce the fault.
Normal / Active
Normal: Consistent CAN communication activity with clean transitions.
Abnormal / Distorted
Abnormal: Noise, distortion, irregular transitions, or intermittent communication.
Inactive / No Communication
Inactive: Expected communication activity is absent at the tested network point.
Important: These are simplified diagnostic illustrations, not manufacturer-specific waveform specifications. Actual CAN High and CAN Low voltage levels, timing, and network behavior must be compared with the specifications for the exact vehicle.
U0157 Diagnostic Signal Flow
↓
Vehicle CAN Communication Network
↓
Telematics Control Module
↓
Cellular / GPS / Connected Services
↓
Other Vehicle Control Modules
U0157 OBD Live Data
Available parameters depend on the vehicle and scan tool. Where supported, useful information may include telematics communication status, system voltage, network status, GPS status, cellular connection status, emergency-service status, and related module information.
Live data should be combined with direct electrical and network testing because intermittent wiring or connector faults may not appear during a stationary scan.
Common Repairs for U0157
- Repair missing telematics module power supply.
- Repair poor or damaged module ground.
- Replace a failed fuse after identifying the cause.
- Repair damaged CAN High or CAN Low wiring.
- Repair loose, corroded, or damaged connectors.
- Repair damaged terminals or wiring harnesses.
- Correct water intrusion.
- Repair another module that is disrupting the communication network.
- Repair or replace the telematics control module when internal failure is confirmed.
- Program, configure, or initialize the replacement module when required.
U0157 Repair Cost
- Electrical/network diagnosis: approximately $100–$200+.
- Fuse or wiring repair: approximately $75–$300+.
- Connector/terminal repair: approximately $80–$250+.
- Telematics module repair: approximately $150–$600+.
- Module replacement and programming: approximately $400–$1,500+ depending on vehicle.
These are general estimates only. Actual costs depend on vehicle model, module type, parts availability, labor rates, and programming requirements.
Common Repair Mistakes
- Replacing the telematics module before checking power and ground.
- Ignoring low battery voltage.
- Failing to inspect the module connector.
- Replacing the module without testing CAN communication circuits.
- Assuming every stored U-code means a failed control module.
- Ignoring another module that may be affecting the CAN network.
- Failing to perform required programming or configuration after replacement.
Related OBD-II Codes
- U0100 – Lost Communication With ECM/PCM.
- U0121 – Lost Communication With Anti-Lock Brake System (ABS) Module.
- U0140 – Lost Communication With Body Control Module.
- U0150 – Lost Communication With Gateway Module "A".
- U0155 – Lost Communication With Instrument Panel Cluster.
- U0156 – Lost Communication With Information Center Module.
FAQ About U0157
Can a weak battery cause U0157?
Yes. Low system voltage can cause the telematics module or other control modules to reset or temporarily stop communicating.
Can a CAN wiring problem cause U0157?
Yes. An open, shorted, damaged, or poorly connected CAN circuit can interrupt communication with the telematics control module.
Does U0157 mean the telematics module is bad?
No. The module's power, ground, fuses, connectors, and communication circuits should be tested before concluding that the module itself has failed.
Can U0157 affect remote vehicle functions?
Yes. If the affected vehicle uses the telematics module for remote services, cellular communication, GPS, emergency assistance, or connected-car features, those functions may become unavailable.
Can an oscilloscope help diagnose U0157?
Yes. An oscilloscope can help identify abnormal CAN activity, electrical noise, distortion, or intermittent communication when a network fault is suspected.
Does a replacement telematics module need programming?
Many vehicles require programming, configuration, coding, or initialization after telematics module replacement. The exact procedure depends on the manufacturer and vehicle.
Final Takeaway
U0157 is a generic OBD-II network communication code indicating lost communication with the Telematics Control Module.
A reliable diagnosis should begin with battery voltage, fuses, module power and ground, connectors, and CAN communication circuits. The telematics module should only be replaced after its electrical supply and network communication have been properly verified.