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DTC codes / BMW codes / P1608

P1608 · BMWSerial Communicating Link Control Module

P1608 on BMW vehicles indicates that the serial communication link between the engine control module (DME) and another control unit has failed or is unreliable. The DME detects a loss of the serial data bus signal, often due to a wiring fault, a failed module, or a power supply issue, and stores this code while illuminating the check engine light.

SystemPowertrain
Code typeBMW specific
SeverityMedium
Fix difficultyProfessional
AreaComputer and output circuits

Symptoms you may notice

  • Check engine light illuminated on the dashboard
  • Often no symptoms besides the warning light
  • Intermittent rough running or stalling if communication affects engine management
  • Transmission may enter limp mode or shift harshly
  • Other warning lights (e.g., DSC, ABS) may appear if multiple modules are affected
  • Reduced fuel economy or performance due to default operating strategies

Common causes, most likely first

  1. Damaged or corroded wiring in the serial communication bus (CAN or K-bus) between the DME and other modules
  2. Failed control module (e.g., transmission control unit, ABS/DSC module) causing bus communication disruption
  3. Poor electrical connections at the DME or other module connectors
  4. Low battery voltage or faulty charging system affecting module communication
  5. Internal fault in the DME itself
  6. Aftermarket accessories improperly wired into the communication bus

How to diagnose and fix it

  1. Perform a battery voltage test and load test; recharge or replace the battery if weak
  2. Use a BMW-specific scan tool to read all module fault codes and identify which modules are not communicating
  3. Inspect and clean the DME and related module connectors for corrosion or loose pins
  4. Check the serial communication bus wiring for continuity, shorts to ground, and shorts to power using a multimeter and wiring diagram
  5. Disconnect suspected faulty modules one at a time to see if communication is restored
  6. Repair or replace damaged wiring or connectors as needed
  7. If all wiring and connections are good, replace the DME or the non-communicating module after proper coding

Before you replace the DME

  • A weak battery is a common cause of serial communication codes on BMWs; always verify battery health before condemning a module.
  • The serial link may involve multiple modules on the same bus, so a single failed module can disrupt communication for others and set P1608.
  • Aftermarket alarms or audio equipment tapped into the bus wiring can introduce interference and trigger this code.
  • P1608 does not always mean the DME is faulty; the code often points to a wiring issue or a different module on the bus.
  • Some BMW models require programming or coding after replacing a module, so a simple swap may not resolve the code.

Can I keep driving with P1608?

If the vehicle runs normally and only the check engine light is on, you can drive cautiously to a repair shop. Avoid long trips or aggressive driving, and if the engine stalls or multiple warning lights appear, stop driving and seek professional diagnosis.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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