CAN network

U0167 — Lost Communication With Immobilizer Control Module

Severity: medium Drive with care, to a shop

What U0167 means

U0167 means the main computer (ECM or PCM) stopped receiving messages from the immobilizer control module over the CAN bus. Normally the immobilizer verifies the key transponder and tells the engine computer that starting is allowed. If that link is lost, the engine computer may block starting.

Symptoms

  • Security or immobilizer light on or flashing
  • Engine cranks but will not start
  • Intermittent starting or no-start
  • Check Engine light on
  • Other modules may also show communication errors on a scan tool

Possible causes

  1. Open or shorted CAN bus wiring between the ECM/PCM and the immobilizer module
  2. Lost power or ground at the immobilizer module (blown fuse, bad connection)
  3. Damaged wiring harness or corroded connectors
  4. Failed immobilizer control module
  5. Faulty antenna ring or key reader
  6. Module and key data mismatch after a replacement or reprogramming
  7. Internal ECM/PCM fault (uncommon)

How to diagnose

  1. Scan all modules and look for other U-codes, which show whether one circuit or the whole network is affected
  2. Check battery voltage and terminals, since low voltage can cause false communication faults
  3. Inspect the fuses that feed the immobilizer module
  4. Measure power and ground at the immobilizer module connector with a multimeter
  5. Inspect connectors and harness for corrosion, damage or past repairs
  6. Test CAN-H and CAN-L for opens and shorts, and check for about 60 ohms between them with power off
  7. Try every key and read the immobilizer status and stored key count
  8. Check the key reader antenna at the ignition switch and review any recent module or key replacements

Common fixes

  • Repair or replace damaged CAN wiring or connectors
  • Restore power and ground to the immobilizer module and replace blown fuses
  • Reprogram or adapt the immobilizer module or ECM/PCM and relearn keys
  • Replace the immobilizer module with a VIN-matched unit and program it
  • Replace the antenna ring if it is faulty

Questions and answers

Why won't my car start with U0167?

The engine computer is not getting confirmation from the immobilizer that the key is valid, so it blocks starting. Check module power, CAN wiring and battery condition first.

Can I just clear U0167?

You can clear it, but if the cause remains the code will return and starting may still be blocked. Find the wiring, power or module fault first.

Can this code appear after replacing a module or key?

Yes. If the new part is not programmed to the vehicle, the data will not match and communication with the immobilizer fails. It needs to be programmed with a scan tool or at a dealer.

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.