CAN network

P0600 — Serial Communication Link Malfunction

Severity: medium Drive with care, to a shop

What P0600 means

P0600 means the engine control module (ECM) detected a fault in its serial communication with other modules. Modules normally share data over a network such as CAN, and the ECM needs a steady flow of messages to run the engine properly. When that exchange breaks down, U-codes often appear alongside it.

Symptoms

  • Check Engine light and other warning lights on
  • Intermittent no-start
  • U-codes stored along with P0600
  • Dead or erratic gauges and instrument cluster
  • Limp mode or reduced power
  • Scan tool cannot talk to some modules

Possible causes

  1. Damaged, open or shorted CAN bus wiring
  2. A failed module pulling the bus down
  3. Corrosion or poor contact at the diagnostic link connector (DLC)
  4. Aftermarket device plugged into the OBD port (alarm, tracker, dongle)
  5. Power or ground problems at the ECM, weak battery
  6. Failed ECM
  7. Poorly installed aftermarket electrical accessories

How to diagnose

  1. Scan all modules, record every code and the freeze frame data
  2. Unplug any device from the OBD port and see if the fault clears
  3. Test battery and charging voltage, and check terminals and grounds
  4. Inspect the DLC for corrosion and bent pins
  5. Measure resistance between CAN-H and CAN-L (about 60 ohms on a healthy bus)
  6. Inspect the harness for damage, water intrusion and past repairs
  7. Unplug suspect modules one at a time to see if communication returns
  8. Check ECM power and ground, and look for a software update

Common fixes

  • Remove the aftermarket device from the OBD port
  • Repair or replace damaged bus wiring or connectors
  • Clean or replace the diagnostic connector
  • Replace the faulty module loading the bus
  • Correct power and ground faults, replace a weak battery
  • Replace or reprogram the ECM

Questions and answers

What does P0600 mean?

It means the engine computer has a problem communicating with other modules over the serial network. Wiring, connectors or a failed module are the usual culprits.

Can I drive with P0600?

Only for a short trip to get it checked. Communication can drop at any time, which may stall the engine or put it in limp mode.

Can a device in the OBD port cause P0600?

Yes. Alarms, trackers and cheap dongles can disturb the network. Unplug them and see if the code stays away.

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.