U0167

Universal

Lost Communication With Vehicle Immobilizer Control Module

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The vehicle’s control modules have detected that they cannot communicate with the immobilizer control module. The immobilizer helps authorize starting, so this fault may cause an anti-theft warning or a no-start condition. It can also be stored without noticeable symptoms. The code identifies a communication problem, not proof that the immobilizer module itself has failed.

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⚠️ Before You Begin (Safety First)

The vehicle may not start, which could leave you stranded. If it starts and runs normally, this code alone does not establish that it is unsafe to drive; stop somewhere safe if the engine stops, drivability changes, or another warning indicates a serious problem. Do not bypass the immobilizer or attempt security-system repairs without the correct vehicle-specific procedures.

Common Symptoms

  • The engine may not start if the vehicle cannot confirm immobilizer authorization.
  • An anti-theft or security warning may appear if the vehicle reports an immobilizer communication problem.
  • The fault may be stored with no noticeable symptoms if communication is intermittent or the vehicle can still authorize starting.
  • Other warning lights or communication-related fault codes may appear if the underlying issue affects multiple modules.

Common Causes

  • A loose, damaged, corroded, or otherwise poor electrical connection to the immobilizer control module.
  • A problem with the module’s power supply or ground connection.
  • Damage or an electrical fault in the vehicle network wiring or connectors.
  • Low or unstable vehicle battery voltage that interrupts module communication.
  • A fault within the immobilizer control module, which should be considered only after its power, ground, and network connections are checked.

Diagnostic Steps

  1. Note whether the vehicle starts and whether a security warning is displayed. This helps establish the current effect of the communication fault.
  2. Check the battery terminals for obvious looseness or corrosion, and look for other signs of a weak battery. Unstable voltage can affect module communication.
  3. With the vehicle safely parked and switched off, visually inspect accessible wiring and connectors for obvious damage or disconnection. Do not pull on wiring or disconnect security-system components without vehicle-specific guidance.
  4. Check only the fuses identified for the relevant systems in the owner’s manual. Replace a blown fuse only with the specified type and rating; if it blows again, stop and seek diagnosis.
  5. If the warning or no-start condition continues, have the vehicle scanned across its modules. A code read from the engine computer alone may not show which module or connection is causing the communication loss.

When to Call a Professional

Use a scan tool that can communicate with the vehicle’s modules to see which modules report the fault and whether the immobilizer module responds. Check for related communication and power-supply codes, then test the module’s power, ground, and network connections using the vehicle-specific wiring information. Confirm the cause before replacing a module; security-related programming or configuration may be required after some repairs.

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Commonly Asked Questions

Does U0167 prove that the immobilizer control module has failed?

No. It reports lost communication with that module. Wiring, connectors, power, ground, battery voltage, or another network issue can cause the same condition.

Can the vehicle still start with U0167?

Yes, it may still start if the communication loss is intermittent or authorization remains available. In other cases, the fault may prevent starting. Exact behavior depends on the vehicle.

Can I clear the code and assume the problem is fixed?

Clearing a code does not repair the cause. If communication is still interrupted, the code or symptoms may return. Record related codes and have the system checked if the fault persists.

Should I replace the immobilizer module first?

Not without testing. A technician should check module communication, power, ground, and network connections first. Some module replacements also require vehicle-specific configuration or security procedures.

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