U0168 is a generic OBD-II network communication diagnostic trouble code indicating that communication with the Vehicle Security Control Module (VSCM) has been lost.
The Vehicle Security Control Module is involved in vehicle security, immobilizer, key authorization, and starting-authorization functions depending on the vehicle. The exact module name, location, wiring, communication network, and security architecture vary by manufacturer, model, and model year.
On some vehicles, the security function may be integrated into another control module such as the BCM, Wireless Ignition Node, Sentry Key module, immobilizer module, electronic ignition system, or another body/security controller.
U0168 Code Details
Code: U0168
Meaning: Lost Communication With Vehicle Security Control Module
Type: Generic OBD-II Network Communication Code
Main System: Vehicle Security / Immobilizer / CAN Network
Common Module Abbreviation: VSCM
What Is the Vehicle Security Control Module?
The Vehicle Security Control Module (VSCM) is an electronic control unit or integrated security function responsible for communication and authorization within the vehicle anti-theft system.
Depending on the vehicle, it may receive information from the ignition system, transponder key, smart key, security antenna, or other body-control components and exchange authorization information with the ECM, PCM, BCM, instrument cluster, or gateway.
The VSCM does not necessarily exist as a separate physical module on every vehicle. Some manufacturers integrate its functions into another control unit.
VSCM Abbreviations and Related Terms
Vehicle Security Control Module
Immobilizer
Body Control Module
Engine Control Module
Powertrain Control Module
Controller Area Network
Passive Anti-Theft System
Wireless Ignition Node
Wireless Control Module
Important: These names are not universal. A manufacturer may use a different module name for essentially the same security function.
Symptoms of U0168
- Security or immobilizer warning light may illuminate.
- Engine may crank but fail to start.
- Engine may start and then stall.
- Intermittent no-start condition.
- Vehicle may operate normally until the next ignition cycle.
- Key authorization may fail.
- Remote or keyless functions may be affected.
- Multiple communication-related U-codes may be stored.
- Scan tool may be unable to communicate with the security module.
- Starting authorization may become unavailable.
Common Causes of U0168
- Weak or discharged battery.
- Low system voltage during cranking.
- Blown fuse supplying the security module.
- Missing module power supply.
- Poor or damaged module ground.
- Open CAN High circuit.
- Open CAN Low circuit.
- Short circuit on the CAN network.
- Damaged or corroded electrical connector.
- Loose or damaged terminals.
- Water intrusion.
- Damaged wiring around the dashboard or steering column.
- Another module interfering with the CAN network.
- Incorrect module configuration.
- Software or programming problem.
- Internal failure of the security control module.
How Serious Is U0168?
U0168 can be a serious communication fault because the vehicle security system may be involved in engine starting authorization.
Depending on the vehicle, loss of communication may cause a no-start condition, an intermittent starting problem, or an engine that starts and then stalls. Some vehicles may continue operating normally until the next ignition cycle.
For this reason, U0168 should not be treated as a simple warning code when security or starting problems are present.
Can You Drive With U0168?
If the vehicle starts and operates normally, it may remain drivable temporarily on some vehicles. However, an intermittent U0168 fault can cause a future no-start condition, particularly after switching the ignition off.
If the vehicle already has a security warning, engine stall, or starting problem, the fault should be diagnosed before relying on the vehicle for normal transportation.
How to Diagnose U0168
1. Perform a Complete Vehicle Scan
Use a professional scan tool to scan all available control modules. Record U0168 together with all other communication, voltage, ignition, body, security, and powertrain codes.
Other active network or battery-voltage codes may need to be diagnosed first because they can be the actual cause of the communication failure.
2. Check Communication With the Security Module
Attempt to access the Vehicle Security Control Module with the scan tool.
If the scan tool can communicate with the module, U0168 may be an intermittent or stored communication fault. If the module cannot be accessed while other modules report U0168, the communication problem may currently be active.
3. Check Battery and Charging Voltage
Check battery condition and charging-system operation before performing advanced network diagnosis.
Low voltage during engine cranking can cause electronic modules to reset or temporarily disappear from the CAN network.
4. Check Security Module Fuses
Use the vehicle-specific fuse diagram to identify all fuses supplying the security system or the module containing the security function.
Do not repeatedly replace a blown fuse without determining why the fuse failed.
5. Test Module Power and Ground
Verify all required battery and ignition power supplies and test the security module ground circuits according to manufacturer specifications.
Loss of power or ground is one of the first conditions that should be checked before condemning a security module.
6. Inspect Connectors and Wiring
Inspect the security module connectors and wiring for:
- Corrosion.
- Loose terminals.
- Bent or damaged pins.
- Water intrusion.
- Damaged insulation.
- Chafed wiring.
- Previous wiring repairs.
- Burned or overheated terminals.
On vehicles where the security module is located behind the dashboard or around the steering column, carefully inspect wiring that may have been disturbed during previous repairs.
7. Check CAN-H and CAN-L
Inspect the CAN communication circuits for opens, shorts, high resistance, damaged insulation, corrosion, or poor connections.
The exact CAN network and pin locations vary between manufacturers. Always use the wiring diagram for the exact vehicle.
8. Check for Another Module Affecting the Network
If several control modules report communication failures, investigate common network, power, ground, and gateway circuits before replacing the security module.
A single defective module or shorted communication circuit can interfere with multiple control units.
9. Check Security and Key Authorization Data
Where supported, use the scan tool to check key recognition, immobilizer status, security status, communication status, and starting authorization.
A key-authorization problem and a communication problem should not automatically be considered the same fault. The security module must first be communicating correctly before its authorization data can be evaluated reliably.
10. Confirm Security Module Failure
The security module should only be considered defective after its power, ground, fuses, connectors, communication circuits, and related modules have been properly tested.
U0168 Oscilloscope Signal Patterns
An oscilloscope can be useful when diagnosing an intermittent CAN communication problem. It can reveal abnormal network activity, electrical noise, distortion, or loss of communication that may not be visible during a basic voltage test.
Normal / Active
Normal: Stable communication activity with consistent transitions.
Abnormal / Distorted
Abnormal: Noise, distortion, irregular transitions, or unstable network activity.
Inactive / No Communication
Inactive: Expected network communication activity is absent at the tested network point.
Important: These are simplified diagnostic illustrations, not manufacturer-specific waveform specifications. Actual CAN-H and CAN-L voltage levels, timing, termination, and waveform behavior must be compared with the specifications for the exact vehicle.
U0168 Diagnostic Signal Flow
↓
Vehicle Security Control Module
↓
CAN-H / CAN-L
↓
BCM / Gateway / ECM / PCM
↓
Security Verification
↓
Engine Start Authorization
U0168 OBD Live Data
Available parameters depend on the vehicle and scan tool. Where supported, useful information may include security-module communication status, key authorization, immobilizer status, system voltage, ignition status, security status, and engine starting authorization.
Live data should be combined with direct electrical testing because intermittent CAN wiring faults and voltage problems may disappear while the vehicle is stationary.
OEM Notes for U0168
Although U0168 has a generic definition, the actual security module can have different names and functions depending on the manufacturer.
Depending on the vehicle, security functions may involve the Wireless Ignition Node (WIN), Sentry Key Remote Entry Module (WCM), BCM, or related security electronics. Some OEM procedures specifically identify U0168 with the WCM/SKREEM on certain models.
Security and immobilizer functions may involve PATS, the BCM, Smart Junction Box, or other vehicle security electronics depending on model and year.
Vehicle security functions may involve the BCM, theft-deterrent system, ECM, or related modules depending on vehicle architecture.
Security and ignition authorization may involve electronic ignition and key-related modules depending on the vehicle platform.
The vehicle security function may be integrated into the BCM, immobilizer module, instrument cluster, keyless-entry system, gateway, or another dedicated security controller.
OEM warning: These examples describe possible architectures only. Always identify the exact security module and network using the factory service information for the vehicle being diagnosed.
Common Repairs for U0168
- Repair missing security-module power supply.
- Repair poor or damaged module ground.
- Replace a failed fuse after identifying the cause.
- Repair damaged CAN-H wiring.
- Repair damaged CAN-L wiring.
- Repair corroded or loose connectors.
- Repair damaged terminals.
- Correct water intrusion.
- Repair another module disrupting the communication network.
- Repair or replace the security control module when internal failure is confirmed.
- Perform required module programming or configuration.
- Perform required immobilizer or key synchronization procedures.
U0168 Repair Cost
- Electrical/network diagnosis: approximately $100–$250+.
- Fuse or wiring repair: approximately $75–$300+.
- Connector/terminal repair: approximately $80–$250+.
- CAN network repair: approximately $100–$400+.
- Security module repair: approximately $150–$600+.
- Module replacement and programming: approximately $400–$1,500+ depending on the vehicle.
These are general estimates only. Actual repair costs depend on vehicle design, module availability, labor rates, programming requirements, and security-key synchronization procedures.
Common Repair Mistakes
- Replacing the security module before checking power and ground.
- Ignoring low battery voltage.
- Replacing the module without testing CAN communication.
- Failing to inspect connectors and terminals.
- Assuming U0168 automatically means the VSCM is defective.
- Ignoring other U-codes stored by other modules.
- Failing to investigate a common CAN network problem.
- Replacing a security module without checking programming requirements.
- Confusing a security-module communication problem with a key-authorization problem.
- Failing to perform required immobilizer initialization after module replacement.
Related OBD-II Codes
- U0167 – Lost Communication With Vehicle Immobilizer Control Module.
- U0100 – Lost Communication With ECM/PCM.
- U0140 – Lost Communication With Body Control Module.
- U0155 – Lost Communication With Instrument Panel Cluster.
- U0160 – Lost Communication With Audible Alert Control Module.
- U0163 – Lost Communication With Navigation Control Module.
- U0169 – Lost Communication With Sunroof Control Module.
Related communication codes should always be interpreted together. Several U-codes appearing simultaneously may indicate a common power, ground, CAN, or gateway problem rather than multiple failed modules.
FAQ About U0168
What does U0168 mean?
U0168 means Lost Communication With Vehicle Security Control Module. It indicates that one or more vehicle control modules are no longer receiving the expected communication messages from the security module.
Can U0168 cause a no-start?
Yes. Depending on the vehicle security architecture, loss of communication with the security module can prevent starting authorization or cause the engine to start and then stall.
Can a weak battery cause U0168?
Yes. Low or unstable voltage can cause security and body modules to reset or temporarily disappear from the CAN network.
Can a CAN wiring problem cause U0168?
Yes. An open, shorted, damaged, or poorly connected CAN circuit can interrupt communication between the security module and other control units.
Does U0168 mean the security module is bad?
No. Power, ground, fuses, connectors, CAN circuits, battery voltage, and other network modules should be checked before replacing the security module.
Can an oscilloscope help diagnose U0168?
Yes. An oscilloscope can help identify abnormal CAN activity, electrical noise, distorted signals, intermittent communication, or loss of network activity.
Does a replacement security module need programming?
Many vehicles require programming, coding, configuration, initialization, or key synchronization after replacing a security-related module. The exact procedure is manufacturer-specific.
Is U0168 the same on every vehicle?
The generic DTC definition is standardized, but the actual module, location, network architecture, diagnostic procedure, and security strategy can differ significantly between manufacturers and model years.
Final Takeaway
U0168 is a generic OBD-II network communication code indicating Lost Communication With the Vehicle Security Control Module.
Because the security system may participate in starting authorization, U0168 can be associated with a no-start, intermittent start, security warning, or engine-stall condition depending on the vehicle.
The most reliable diagnostic approach starts with scanning all modules, checking battery voltage, verifying fuses, testing module power and ground, inspecting connectors, checking CAN-H and CAN-L, and determining whether another module is affecting the network.
Do not replace the security module simply because U0168 is stored. Confirm the electrical supply and communication network first, then follow the manufacturer's programming and security procedures if module replacement is required.