OBD Code U0167: Lost Communication With Immobilizer – Causes & Fixes

Quick Answer

The U0167 diagnostic trouble code indicates that your vehicle’s main computer (PCM/ECM) cannot communicate with the immobilizer control module. The immobilizer is a critical anti-theft system that prevents the engine from starting if an unauthorized key is used. When communication is lost, your vehicle may not start, or you may experience intermittent starting issues. This is a serious code that requires prompt diagnosis and repair.

What Does U0167 Mean?

U0167 is a network communication diagnostic trouble code that falls under the “U” category, which covers data bus and module communication errors. Specifically, this code indicates that the primary control module (typically the PCM or ECM) has detected a loss of communication with the vehicle immobilizer control module.

The immobilizer control module is responsible for:

• Verifying the authenticity of your vehicle key or key fob
• Sending authorization signals to the engine control module
• Preventing engine start if an invalid key is detected
• Managing the security system communication

When the U0167 code is triggered, it means the PCM has not received expected communication from the immobilizer module for a specified period, typically over several ignition cycles. This breaks the security chain and prevents normal engine operation.

Common Symptoms

• Engine won’t start: The most common symptom; the engine cranks but won’t turn over
• Intermittent starting issues: Vehicle starts sometimes but not consistently
• Check Engine Light (CEL): Illuminated on the dashboard
• Security light stays on: The immobilizer or security indicator light remains lit
• Key fob not working: Remote lock/unlock functions may fail
• Stuck in limp mode: Vehicle may run but with reduced power or limited RPM
• Multiple warning lights: PCM, security, and battery warning lights may appear together
• No communication with diagnostic scanner: Scanner may show module not responding

Possible Causes

Listed from most to least common:

1. Faulty Immobilizer Control Module – The module itself has failed internally and cannot communicate. This is the most common cause and typically requires module replacement.
2. Damaged Wiring or Connectors – Corroded, loose, or broken wires between the immobilizer module and PCM prevent signal transmission. Check all connections thoroughly.
3. Failing PCM/ECM – The main engine control computer may have a communication circuit failure that prevents it from reaching the immobilizer module.
4. Battery or Charging System Issues – Low voltage or inconsistent power supply can cause communication failures. A weak battery may not provide enough power for proper module operation.
5. CAN Bus Network Failure – Modern vehicles use a CAN (Controller Area Network) bus for module communication. A failure in this network prevents all module-to-module communication.
6. Defective Key or Key Fob – A faulty key transponder may cause the immobilizer to malfunction and stop communicating with the PCM.
7. Aftermarket Security System Interference – Poorly installed aftermarket alarms or security systems can interfere with immobilizer communication.
8. Software or Firmware Issues – Outdated or corrupted PCM software may lose the ability to communicate with the immobilizer module.
9. Water Damage or Corrosion – Moisture intrusion into electrical connectors or modules causes corrosion and communication loss.

Diagnostic Steps

Follow these steps to diagnose the U0167 code:

Step 1: Scan for Additional Codes

Connect a professional OBD-II scanner to the vehicle’s diagnostic port. Note all present and historical codes. Related codes like U0101 (PCM communication), U0140 (Body Control Module communication), or immobilizer-specific codes will help narrow down the issue.

Step 2: Check Battery Voltage

Use a multimeter to verify battery voltage is at least 12.6V with the engine off, and 13.5-14.5V while running. Low voltage is a common cause of communication failures. Test the charging system if voltage is low.

Step 3: Inspect Wiring and Connectors

Locate the immobilizer control module (usually near the steering column, under the dashboard, or in the engine bay—consult your service manual for exact location). Inspect all connectors for:

• Corrosion or oxidation
• Loose or bent pins
• Water damage or moisture
• Damaged insulation on wires

Clean connectors with electrical contact cleaner and ensure they’re fully seated.

Step 4: Check CAN Bus Network

Using a scanner with CAN bus diagnostics, test communication on the vehicle’s data bus network. Check for proper voltage levels on CAN High and CAN Low lines (typically 2.5V each at idle).

Step 5: Test Immobilizer Module Directly

If available, use a scanner capable of communicating directly with the immobilizer module. Attempt to read module data and perform module-level diagnostics. If the scanner cannot reach the module, communication is definitely lost.

Step 6: Check for Aftermarket Modifications

Inspect the vehicle for any aftermarket security systems, alarm systems, or remote start installations. These can interfere with immobilizer communication. Disconnect them temporarily to test.

Step 7: Perform a System Reset

Disconnect the negative battery terminal for 15 minutes to clear temporary faults and reset modules. Reconnect and attempt to start the vehicle. If the code returns immediately, the issue is persistent.

Step 8: Professional Diagnosis

If the above steps don’t resolve the issue, the vehicle requires professional diagnostic equipment. A technician may need to:

• Access module programming data
• Perform network communication tests
• Check for TSBs (Technical Service Bulletins) for your vehicle
• Replace the immobilizer module or PCM

Repair Cost Estimates

Repair costs for U0167 vary significantly based on the root cause and vehicle make/model:

• Connector/Wiring Repair: $100–$300 (most affordable option if the issue is loose or corroded connections)
• Immobilizer Module Replacement: $400–$1,200 (includes parts and labor; varies by vehicle complexity)
• PCM/ECM Replacement: $1,000–$3,500 (expensive; requires programming and key coding)
• CAN Bus Network Repair: $300–$800 (depends on extent of wiring damage)
• Battery Replacement: $100–$300 (if low voltage is the cause)
• Diagnostic Labor Only: $100–$200 per hour (may be required before determining the fix)

Note: Luxury and European vehicles (BMW, Mercedes, Audi) typically cost 20–40% more than domestic vehicles due to specialized parts and programming requirements.

Can I Still Drive?

Severity: High – Do Not Drive

The U0167 code is serious and you should not drive the vehicle until it’s repaired. Here’s why:

• Engine May Not Start: If the immobilizer cannot communicate with the PCM, the engine may refuse to start, leaving you stranded.
• Intermittent Starting: Even if the vehicle starts, it may shut off unexpectedly while driving, creating a safety hazard.
• Security Risk: A non-functional immobilizer means the vehicle is vulnerable to theft.
• Limp Mode Operation: The vehicle may run in a reduced-power state, limiting acceleration and highway capability.
• Potential for Strand: You could be stranded if the vehicle fails to start during your commute.

Recommendation: Have the vehicle towed to a qualified repair facility or dealership. Do not attempt to drive it long distances.

Frequently Asked Questions

Q: Can I drive my car with the U0167 code?

A: It’s not recommended. While some vehicles may still start and run, the immobilizer communication loss is a serious issue that can cause the engine to shut off while driving or prevent starting altogether. Have it diagnosed and repaired as soon as possible. If the vehicle won’t start at all, have it towed.

Q: Will the U0167 code clear on its own?

A: No, this code will not clear without repair. It’s a persistent communication fault that requires fixing the underlying issue—whether that’s repairing wiring, replacing the immobilizer module, or addressing a PCM problem. Clearing the code without fixing the cause will result in it returning immediately.

Q: Is U0167 the same as an immobilizer failure?

A: Not necessarily. U0167 indicates a communication loss with the immobilizer module, but the module itself may be functional. The problem could be wiring, connectors, the PCM, or the CAN bus network. However, if the immobilizer module is faulty, it will cause this code. Professional diagnosis is needed to determine which component is actually failing.

Q: How much does it cost to fix a U0167 code?

A: Costs range from $100–$3,500 depending on the cause. Simple connector cleaning or wiring repair might cost $100–$300. Replacing an immobilizer module typically costs $400–$1,200. PCM replacement is the most expensive at $1,000–$3,500. Diagnostic labor is usually $100–$200 per hour. Get a quote from your mechanic after diagnosis.

Q: Can a dead battery cause the U0167 code?

A: Yes, a weak or dead battery can cause communication faults including U0167. Low voltage prevents modules from communicating properly on the CAN bus network. Always check your battery voltage first (should be 12.6V or higher). If the battery is low, charge or replace it and see if the code clears. However, if the code persists after battery replacement, the issue is elsewhere.

Q: Do I need to replace my key fob if I get U0167?

A: Not necessarily. While a faulty key fob can contribute to immobilizer issues, U0167 specifically indicates a communication loss between the immobilizer module and the PCM. This is usually a wiring, connector, or module issue rather than a key fob problem. However, your technician may test the key fob as part of the diagnostic process.