OBD-II Code U0168: Lost Communication With Vehicle Security Control Module

What Does U0168 Mean?

Code U0168 means the engine computer lost communication with the Vehicle Security Control Module (VSCM). The VSCM controls the anti-theft system, immobilizer, and key fob. Without this connection, the system cannot verify your key, forcing the immobilizer to block the engine from starting.

Technical definition: Lost Communication With Vehicle Security Control Module. This indicates the VSCM is not receiving or transmitting messages on the Controller Area Network (CAN) bus, the data network that allows the vehicle's electronic modules to interact.

Can I Drive With U0168?

No — Do Not Drive. If the engine refuses to start, driving is impossible. If the problem is intermittent and the engine does start, driving risks stranding you without warning. The immobilizer often re-engages during your next restart attempt, leaving you stuck. While it won't damage other components, the unpredictability makes driving unsafe.

Common Causes

• Weak battery or faulty charging system (Very Common) — Low voltage is the primary cause of communication codes. A weak battery causes electronic modules to crash during startup, triggering random communication errors like U0168. The battery must maintain above 9.6V during cranking to keep modules online.
• Blown fuse or poor power/ground connection (Very Common) — The security module requires a stable 12-volt power supply and a solid ground connection. A blown fuse or a corroded ground wire interrupts power, forcing the module offline instantly.
• Damaged wiring or loose connectors (Common) — The wires linking the security module to the CAN bus network corrode, fray, or disconnect. Moisture intrusion from humidity, road salt, or windshield leaks is the most frequent culprit.
🎬 Watch: How to fix water damage and corrosion in the module
• Faulty Vehicle Security Control Module (VSCM) (Less Common) — The module fails internally due to age, heat, or moisture. This often presents as a cold solder joint on the circuit board that creates an open circuit when cold, causing a no-start on cold mornings that disappears as the interior warms up.
• Interference from aftermarket electronics (Less Common) — Improperly installed aftermarket alarms, remote starters, or stereo systems interfere with the CAN bus network, disrupting communication and triggering the code.
• Software corruption or glitch (Rare) — The module's software corrupts after a severe voltage spike or a failed programming attempt. A temporary glitch is often resolved by a hard battery reset, 🎬 See how to perform a soft reset and replace the TIPM while deeper issues require a dealer firmware reflash.
• CAN bus network failure (Rare) — The CAN bus network requires a 120-ohm resistor at each end. If a terminating resistor fails or the main network wiring breaks, it causes widespread communication errors across multiple modules.

Symptoms

• Engine cranks but won't run, or won't crank at all — The immobilizer activates because it cannot verify the key, preventing the engine from starting as a theft deterrent.
• Flashing or solid security/anti-theft light — A red or amber light on the dashboard, shaped like a key or a padlock, 🎬 Watch: Troubleshooting a Chevy crank-no-start with a flashing security light illuminates to indicate a critical fault in the security system.
• Key fob and power locks are inoperative — Remote functions like lock, unlock, and panic fail because the module responsible for receiving these wireless signals is offline.
• Alarm system malfunctions — The vehicle's alarm fails to arm when locking the doors, or triggers randomly while parked.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Charge or replace weak battery — Parts: $150-$350, Labor: $0-$50, ~0.5 hr book time (DIY)
• Replace blown fuse(s) — Parts: $1-$10, Labor: $0-$25, ~0.1 hr book time (DIY)
• Repair damaged wiring or clean corroded connectors/grounds — Parts: $5-$50, Labor: $100-$400, ~2 hr book time (Intermediate)
  : OEM 19210255 (Alt: {"brand": "Painless Performance", "number": "10101 (Universal Kit)"})
• Reflash or update module software — Parts: $0, Labor: $125-$250, ~1 hr book time (Professional)
• Replace and reprogram the Vehicle Security Control Module — Parts: $400-$900, Labor: $150-$300, ~2.5 hr book time (Professional)
  : OEM 68244876AA (Alt: {"brand": "Dorman", "number": "599-900, 599-913, 599-931"})
  : OEM L1MZ-14A068-C (Alt: {"brand": "Cardone", "number": "73-80209"}, {"brand": "Dorman", "number": "599-980"})
  : OEM 23451736

DIY vs Professional

• Charge or replace weak battery — Beginner:
  Tools: Wrenches, battery terminal cleaner, safety glasses.
• Replace blown fuse(s) — Beginner:
  Tools: Fuse puller, owner's manual.
• Repair damaged wiring or clean corroded connectors/grounds — Beginner:
  Tools: Multimeter, wire strippers, soldering iron, heat shrink tubing, contact cleaner.
• Reflash or update module software — Beginner:
  Tools: Professional diagnostic scan tool with J2534 pass-thru device and manufacturer software subscription.
• Replace and reprogram the Vehicle Security Control Module — Beginner:
  Tools: Professional diagnostic scan tool with manufacturer-specific programming capabilities.

Used vs. New Parts: Buying Guide

When a used part is worth it: For older vehicles where a new OEM module is cost-prohibitive. A used module from a reputable recycler is viable if it matches the exact part number and the shop agrees to program it.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Match the part number exactly. Superseded numbers often fail to communicate.
• Ensure the donor vehicle had the exact same options (e.g., remote start).
• Avoid parts from flood-damaged or rust-belt vehicles.
• Buy from a seller offering a 30-90 day warranty.

Decision logic:

• If The part is a Chrysler TIPM with a known high failure rate → Buy a new or professionally remanufactured unit with an updated design.
• If Vehicle is less than 10 years old and the part is under $500 new → Buy new for the longer warranty and guaranteed compatibility.
• If A used part requires dealer programming → Confirm the dealer is willing to program a customer-supplied used part before buying.

Warranty tradeoff: Used parts carry a 30-90 day warranty covering only the part. New aftermarket parts offer 1-year to lifetime warranties. New OEM parts offer 1-2 year warranties.

Worst-case if a used part fails: $300-$600 if a used module is dead on arrival, covering repeat diagnostic and programming labor.

What Happens If You Wait — Timeline

1. First Occurrence: An intermittent no-start occurs, often in cold weather or high humidity. The car starts after several attempts. The security light flashes. (MPG impact: 0%% · Added cost: $0)
2. 1-4 weeks: The frequency of the no-start condition increases. Repeatedly cranking the engine puts significant strain on the battery and starter. (MPG impact: 0%% · Added cost: $100-$250 for a diagnostic fee.)
3. 1-3 months: The intermittent failure becomes a hard failure. The vehicle is permanently disabled and will not start under any conditions. (MPG impact: 0%% · Added cost: $100-$300 for a tow. An additional $150-$350 if the battery was destroyed by repeated cranking.)
4. 3+ months (Post-Failure): The vehicle remains unusable. There is no risk of further component damage, but the primary consequence is the complete loss of vehicle use. (MPG impact: 0%% · Added cost: $700-$1,200 for module replacement and programming.)

Cost of Not Fixing It

• Immediate: Vehicle will not start, stranding the driver. Key fob and alarm functions fail. (Added cost: $100-$300 for a tow.)
• 1-3 months: An intermittent no-start becomes permanent. Continued attempts to start drain and destroy the battery. (Added cost: $150-$350 for a new battery.)
• 3+ months: The vehicle is completely unusable. There is no risk of cascading mechanical damage. (Added cost: $0 in additional damage, but total loss of vehicle utility.)

Diagnosis Steps

1. Perform a Full Vehicle Scan and Load Test Battery
   Use an OBD-II scanner to check for codes in ALL modules. A weak battery causes 'ghost' communication codes. Ensure the battery is fully charged (12.6V at rest) and load-test it. It must hold above 9.6V during cranking.
   Tools: OBD-II Scanner, Multimeter, Battery Load Tester (Beginner)
2. Perform a Hard Reset
   Disconnect both battery terminals and touch the positive and negative cable ends together for 10 minutes. This drains residual power from all modules and clears temporary software glitches. Reconnect and test.
   Tools: Wrench (10mm or 13mm typically) (Beginner)
3. Check Fuses and Relays
   Locate the fuses for the security module, immobilizer, and Body Control Module. Visually inspect them and test with a multimeter for continuity. Replace any blown fuses.
   Tools: Multimeter, Owner's Manual, Fuse Puller (Beginner)
4. Visually Inspect Wiring and Connectors
   Locate the VSCM (often on the steering column, behind the glove box, or integrated into the BCM). Inspect its connector and nearby wiring for corrosion (green/white powder), water damage, or chafing.
   Tools: Flashlight, Trim Removal Tools (optional) (Intermediate)
5. Check for Power and Ground at the Module
   Using a wiring diagram, back-probe the module's connector. With the key on, verify it receives full battery voltage (12.0V-12.6V). Check the ground wire by measuring resistance to the chassis; it must be less than 0.1 ohms.
   Tools: Multimeter, Vehicle-specific Wiring Diagram, Back-probe Kit (Advanced)
6. Check CAN Bus Communication Lines
   With the battery disconnected, measure resistance between CAN High and CAN Low at the OBD-II port. A reading of ~60 ohms means the network is intact. ~120 ohms means an open wire or missing terminating module. With the battery connected and key on, verify ~2.6V on CAN High and ~2.4V on CAN Low.
   Tools: Multimeter, Wiring Diagram (Advanced)
7. Perform a Parasitic Draw Test
   If the battery dies overnight, the security module may be failing to 'go to sleep'. Connect a multimeter in series with the negative battery terminal. If the draw exceeds 50mA, pull the security module fuse. If the draw drops, the module is faulty.
   Tools: Multimeter (with 10A milliamp setting) (Advanced)
8. Scan Tool Network Analysis
   Use a professional scan tool to poll all modules on the bus. This confirms if the VSCM is the only module offline. Monitor CAN bus error counters to identify intermittent wiring problems.
   Tools: Advanced Bi-Directional Scan Tool (Professional)
9. Attempt Module Reflash
   If power, ground, and CAN wiring are intact, the fault is internal to the module. Check for manufacturer software updates (TSBs). A dealer reflash resolves software corruption; if it fails, replace the module.
   Tools: Advanced Scan Tool with Programming Capability (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Vehicle Speed: 0 mph (During key-on or cranking)
• RPM: 0-200 RPM (Engine is off or attempting to start)
• System Voltage: 10.0-12.5V (May be low if a weak battery is the root cause)
• Module Status: Not Communicating (The code sets when the VSCM fails to send its status message for 2.5 seconds.)

Related Codes

• U0100 — Lost Communication with ECM/PCM. If the ECM cannot communicate with the security module, it will not allow the engine to start.
• B2204 — ECU Configuration Mismatch. Indicates the VIN stored in the security module does not match the VIN in the engine computer.
• U0140 — Lost Communication With Body Control Module (BCM). Security functions are often integrated into the BCM.
• P1610 / P1614 — NATS Malfunction (Nissan). Indicates a problem with the Nissan Anti-Theft System failing to verify the key.

Climate & Environmental Factors

• Cold Weather: Cold temperatures cause metal to contract, separating microscopic cracks in solder joints on a module's circuit board. This creates an open circuit and a no-start condition that disappears as the interior warms up. Cold also reduces battery efficiency, making low voltage faults more likely.
• High Humidity & Road Salt: Moisture and road salt create a highly corrosive electrolyte solution. This aggressively attacks wiring, connector pins, and ground points, causing high resistance or open circuits that sever communication.

How to Talk to a Mechanic About This Code

Say this: "My car has a no-start condition with a U0168 code. I'd like to book a diagnostic appointment. Please start by load-testing the battery and checking for power and ground at the security module connector before recommending a module replacement."

This signals that you understand the common causes are often simple electrical issues. It directs the technician to follow a logical diagnostic path and prevents them from jumping to the most expensive conclusion.

Avoid saying:

• 'My car won't start, the security light is on.' (Too vague, invites an expensive diagnostic process)
• 'Just replace the security module.' (You may pay for a part you don't need)
• 'I think the computer is bad.'

Questions to ask before authorizing the repair:

• Did you confirm the battery holds a charge above 9.6V under load?
• What were the voltage and ground resistance readings at the module's main connector?
• Did you check the CAN bus resistance at the OBD-II port? What was the reading?
• If the module needs replacement, does your estimate include programming the new module and relearning my keys?
• What is the warranty on the new part and the labor?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended if a module replacement and programming are confirmed necessary.
  Best for: Vehicles under warranty., Complex cases where a module replacement is confirmed, as they have guaranteed access to programming tools., Manufacturer-specific quirks that independent shops may not know.
  Downsides: Highest labor rates., May replace a whole module assembly rather than diagnose a specific wiring fault. (Typical cost: +50% vs. baseline)
• Independent Shop: Best fit for initial diagnosis. Ask if they have the capability to program security modules for your specific vehicle before committing.
  Best for: Out-of-warranty vehicles where cost is a major factor., Initial diagnosis of electrical systems (battery, fuses, wiring).
  Downsides: Quality varies greatly. Ensure the shop has advanced diagnostic tools., May lack the specific tools to program a new security module. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID for diagnosing a U0168 code. Their business model is not suited for electrical troubleshooting.
  Best for: Battery replacement if identified as the root cause.
  Downsides: Technicians lack specialized training for complex network diagnostics., High pressure to sell parts leads to misdiagnosis. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's private-party value, seriously consider not fixing it.

• Car worth $8000, fix is $1200: Fix it. The repair cost is only 15% of the vehicle's value.
• Car worth $4000, fix is $1200: Borderline. At 30% of the car's value, get a second opinion. The fact the car doesn't run makes selling it difficult.
• Car worth $2000, fix is $1200: Walk away. The repair is 60% of the car's value and is not economically viable.

What Scan Tool You Need for This Code

Minimum: A scanner that reads codes from ALL vehicle modules (BCM, ABS, Airbag), not just standard engine codes, and displays live data.

A basic $20 code reader only tells you the engine computer logged U0168. It cannot tell you if the BCM or ABS modules are also offline. A network-wide outage points to a wiring problem, while a single offline module points to a specific module failure.

Budget: BlueDriver Pro (~$100) — Reads enhanced codes from all modules, providing a full system health report to see exactly which modules are offline.

Mid-range: Foxwell NT680 Pro / Innova 5610 (~$350) — Offers bidirectional controls to actively test components and provides detailed network status information.

Professional: Autel MaxiCOM MK808 / MK906BT (~$500-1200) — Provides full bidirectional control, network topology views, and the module programming functions required after replacing a security module.

Rent vs buy: Buying a budget pick like the BlueDriver is a smart investment to properly diagnose the scope of the problem before paying a shop's diagnostic fee.

How to Clear the Code After You Fix It

1. Reconnect battery if disconnected for repair.
2. Use an OBD-II scan tool to clear the U0168 and related fault codes.
3. Perform a 'soft reset' by turning the key to the 'ON' position for 2 minutes before starting the engine.
4. Verify the security light goes out and the engine starts and runs.

Drive cycle (~20 minutes): A specific drive cycle is not required for a U-code. The system self-tests at key-on. Cycle the key off and on a few times; if the repair was successful, the code will not return. For emissions readiness monitors to reset after a battery disconnect, drive 20-30 minutes in mixed city/highway conditions.

Readiness monitors affected: Evaporative System, Catalyst, O2 Sensor

Before emissions retest: drive at least 50 miles to fully set monitors.

Watch out for:

• Clearing the code will not fix the problem; it returns instantly if the root cause is not repaired.
• After a battery disconnect, emissions readiness monitors read 'Not Ready', causing an automatic smog test failure until a full drive cycle is completed.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: A U0168 code causes an automatic failure. After repair, a full drive cycle must be completed to set readiness monitors before a retest.
• New York: Any check engine light is an automatic failure of the NYS emissions inspection. Readiness monitors must also be set to 'Ready'.
• Texas: In counties requiring emissions testing, a check engine light results in an automatic failure. The vehicle will not pass until the code is cleared and monitors are set.

Most Commonly Affected Vehicles

• Dodge/Chrysler/Jeep Ram, Grand Cherokee, Town & Country, Caliber (2006-2016) — These vehicles use a Totally Integrated Power Module (TIPM), a known high-failure item. Internal failures commonly cause U0168 and fuel pump problems. The security module is often called the Wireless Control Module (WCM) or SKREEM.
• Ford F-150, F-250/F-350 Super Duty, Fusion, E-Series Van (2004-2014) — Security functions are part of the Smart Junction Box (SJB). Water intrusion from windshield leaks is a primary cause of SJB failure, leading to severe corrosion and communication loss.
• GMC/Chevrolet Yukon, Sierra, Silverado, Tahoe (2007-2013) — The wiring harness in the steering column chafes and breaks from frequent use of the tilt/telescoping wheel feature, causing an intermittent loss of communication with column-mounted modules.
• Nissan Altima, Maxima, Rogue (2007-2015) — The Nissan Anti-Theft System (NATS) is highly sensitive to aftermarket alarms. The immobilizer antenna ring around the ignition switch fails or is disrupted by poorly installed remote starters.
• Hyundai/Kia Elantra, Forte, Optima (2011-2018) — The instrument cluster acts as a gateway for the CAN bus. A failure within the cluster disrupts network communication and causes U0168, even if the security module is functional.
• Subaru Outback, Forester, Impreza (2010-2019) — The Body Integrated Unit (BIU) handles security and immobilizer functions. Failure of the BIU is a known issue that leads directly to a U0168 code and a no-start condition.
• Volkswagen/Audi Jetta, Golf, A4 (2005-2015) — The immobilizer system is integrated into the instrument cluster or the Comfort Control Module (CCM). A fault in either component prevents key recognition and logs this code.
• Mazda CX-5, Mazda3, Mazda6 (2013-2020) — Mazda vehicles are highly sensitive to battery voltage. A failing battery causes multiple 'Vehicle System Malfunction' warnings and logs U0168 before the vehicle fails to start.

Manufacturer-Specific Notes

• Chrysler/Dodge/Jeep: The Totally Integrated Power Module (TIPM) is the central point of failure. Internal relay and circuit board failures directly cause U0168. A widespread issue with the internal fuel pump relay led to recalls where dealers installed an external relay to bypass the faulty internal one.
• Ford: Ford integrates security functions into the Smart Junction Box (SJB). A well-documented point of failure is water leaking from a bad windshield seal or cracked cowl panel directly onto the SJB, causing severe corrosion.
• General Motors (GM): On trucks and SUVs with adjustable steering columns, the wiring harness passing through the column frays from the tilt/telescope action. Wiggling the steering wheel while trying to start the car often temporarily restores the connection.
• Nissan: The Nissan Anti-Theft System (NATS) is notoriously sensitive to aftermarket remote starters. Installers cut into the wiring for the immobilizer antenna at the ignition switch, creating poor connections that cause intermittent no-starts.

Real Owner Stories

2006 Dodge Ram 2500 with a sudden no-start

The owner shut the truck off, and five minutes later it cranked but wouldn't start. The red security light stayed solid, and every module reported code U0168.

What they tried:

1. Checked all fuses in the Totally Integrated Power Module (TIPM).
2. Removed an aftermarket performance module.
3. Performed a hard reset by disconnecting the batteries and touching the positive and negative cable ends together for 10 minutes.

Outcome: After the hard reset, the security light went out and the truck started normally. The issue was a temporary software glitch or 'logic lock' in the module.

Lesson: For a sudden, unexplained communication failure, always try a hard battery reset first. It costs nothing and resolves temporary software lockups.

2011-2013 Jeep Grand Cherokee / Dodge Durango with intermittent stalling

The vehicle intermittently stalled while driving and refused to start afterward, accompanied by a U0168 code.

What they tried:

1. Replaced batteries and starters with no success.
2. Diagnosed the internal fuel pump relay within the TIPM as the failure point.

Outcome: Chrysler issued a safety recall (NHTSA 14V-530) to address the faulty internal relay. The official fix installs an external relay to bypass the failing one inside the TIPM.

Lesson: On affected Chrysler, Dodge, and Jeep models, a U0168 code combined with stalling strongly indicates a TIPM failure. Check for open recalls before paying for repairs.

Ford F-150 with electrical issues after rain

The owner experienced an intermittent no-start, flashing security light, and dead power windows immediately following heavy rain.

What they tried:

1. Checked the battery and fuses.
2. Wiggled wires under the passenger dash, which temporarily restored power.

Outcome: A degraded windshield cowl seal allowed water to drip directly onto the Smart Junction Box (SJB). The water corroded the SJB's internal circuits, causing the U0168 code. The fix required replacing the SJB and sealing the cowl leak.

Lesson: On Ford trucks and SUVs, a U0168 code coupled with random electrical faults requires an immediate inspection for water intrusion in the passenger footwell.

How to Prevent This Code From Triggering

• Clean Battery Terminals and Chassis Ground Points (Every 12 months or during oil change) — Corrosion on battery terminals or the main chassis ground creates resistance, leading to low voltage conditions that trigger communication codes. Cleaning these points ensures a solid electrical foundation.
• Apply Dielectric Grease to Critical Connectors (Anytime a connector is disconnected for service) — Dielectric grease seals out moisture and oxygen, preventing corrosion on connector pins. Applying a thin layer to module connectors prevents water intrusion and future communication failures.
• Check for and Clear Known Water Leak Paths (Every 12-24 months, especially on known problem vehicles) — Clogged cowl drains or bad windshield seals allow water to leak directly onto sensitive electronics. Regularly cleaning debris from the cowl area prevents catastrophic module failure.
• Use a Battery Maintainer for Stored Vehicles (Whenever the vehicle is stored for more than 2 weeks) — A battery maintainer prevents the battery from discharging during storage. This ensures modules receive stable voltage upon startup, preventing voltage spikes that corrupt software.

Frequently Asked Questions

Can a weak battery cause code U0168?

Yes. A weak battery is one of the most common causes of communication codes. When voltage drops below 9.6V during cranking, electronic modules crash and lose communication, setting codes like U0168.

How much does it cost to fix U0168?

Costs range from $0 for a battery reset to $1,200 for a module replacement. A new battery costs $150-$350. Replacing and programming the security module typically costs between $700 and $1,200.

Will clearing the code fix the problem?

No. Clearing the code only turns the light off temporarily. The code returns immediately as soon as the modules fail to communicate again.

What is a hard reset and can it fix U0168?

A hard reset involves disconnecting both battery cables and holding them together for 10 minutes to drain residual electricity. This resolves temporary software glitches or 'logic locks'. It is a valid, free diagnostic step to try first.

My car wouldn't start this morning, but it started fine this afternoon. What is the cause?

This indicates an intermittent electrical connection, often related to temperature. A cracked solder joint inside the security module or a corroded connector pin fails to make contact when cold. As the interior warms up, the metal expands, restores the connection, and allows the car to start.

Why won't my car start with a U0168 code?

Your car's immobilizer is an anti-theft feature. To start, the security module must read a code from your key and send an 'all clear' signal to the engine computer. When U0168 is present, that signal is lost, and the engine computer blocks the start.

My key fob stopped working. Is this related to U0168?

Yes. The Vehicle Security Control Module receives signals from your key fob. When it loses power or communication, your remote lock and unlock functions stop working simultaneously.

Key Takeaways

• Code U0168 triggers the vehicle's immobilizer, resulting in an immediate no-start condition and a flashing security light on the dashboard.
• Test the battery under load before replacing any parts; voltage must remain above 9.6V during cranking to prevent communication failures.
• Inspect the Totally Integrated Power Module (TIPM) on 2006-2016 Chrysler, Dodge, and Jeep vehicles, as internal relay failures are the primary cause of this code for these makes.
• Check the passenger-side kick panel on 2004-2014 Ford vehicles for water intrusion, which corrodes the Smart Junction Box (SJB) and severs module communication.
• Budget $550 to $1,200 if the Vehicle Security Control Module requires replacement, as the new unit mandates professional programming to sync with your existing keys and VIN.