CAN network

U0168 — Lost Communication With Vehicle Security Control Module

Severity: medium Drive with care, to a shop

What U0168 means

U0168 means one or more control modules stopped receiving messages from the vehicle security control module over the CAN bus. This module typically handles the immobilizer and anti-theft functions and confirms the key before the engine may start. When communication drops, modules cannot exchange data, and starting or security functions may fail.

Symptoms

  • Security or immobilizer light on or flashing
  • Key fob does not lock or unlock the doors
  • Engine fails to start or stalls
  • Alarm will not arm or disarm
  • Several warning lights on at once
  • Features tied to the affected module unavailable

Possible causes

  1. Open, shorted or corroded CAN bus wiring or connectors
  2. Lost power or ground at the security control module
  3. Failed security module or another faulty module on the bus
  4. Low or unstable battery voltage
  5. Chafed or damaged wiring harness
  6. A faulty module loading down the CAN bus
  7. Corroded terminals in a connector

How to diagnose

  1. Test battery voltage and inspect the terminals
  2. Run a full-vehicle scan to see which modules do not respond
  3. Review freeze frame data and note whether the fault is constant or intermittent
  4. Inspect the security module connector and harness for corrosion, moisture and chafing
  5. Check the module's fuses, power feed and ground
  6. Measure CAN bus resistance (usually about 60 ohms between CAN-H and CAN-L) and voltages at the diagnostic connector
  7. Unplug suspect modules one at a time only by a documented procedure
  8. If power and bus check out, verify the key and its registration in the system

Common fixes

  • Repair or replace damaged CAN wiring and connectors
  • Restore power and ground to the security module
  • Charge or replace a weak battery
  • Replace the security module, matched to the VIN and programmed
  • Replace a faulty module that is disturbing the bus

Questions and answers

What does U0168 mean?

It means the car lost CAN bus communication with the vehicle security control module. Wiring, module power or the module itself is the usual cause.

Why won't my car start with U0168?

The immobilizer may not be able to confirm the key, so the engine controller can block starting. Check the battery and the module's power and ground first.

Can I drive with U0168?

If the car runs, you can usually get to a shop, but a restart is not guaranteed. Have it diagnosed as soon as you can.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.