OBD-II Code P0600 — What It Means & How to Fix It

What Does This Error Mean?

P0600 means the engine computer detected a communication failure on its serial data link. Modern vehicles use a network (called CAN bus) where all the control modules talk to each other. When that network has a problem, P0600 is set. You may see multiple warning lights on at once, erratic instrument readings, or the car may not start. This is a serious code that requires proper diagnosis — often at a shop with advanced scan tools.

Affected Models

All vehicles 1996+
Common in GM vehicles
Common in Ford vehicles
Common in Chrysler, Dodge, and Jeep vehicles
Common in any vehicle with multiple control modules

Common Causes

Faulty wiring in the CAN bus network — damaged, shorted, or open data wires
A failing control module (ECM, TCM, BCM) dragging down the network communication
Corroded or damaged connector on one of the modules on the network
Weak or failing battery causing voltage drops that disrupt module communication
Water intrusion into a control module causing internal damage

How to Fix It

Start by checking battery voltage. A weak battery can cause communication failures across all modules. Test the battery and charging system before going further.

Many P0600 cases are resolved simply by replacing a failing battery or cleaning corroded battery connections.
Check for other codes stored in all modules, not just the engine computer. Use a full-system scan tool. If multiple modules show communication errors, the problem may be in the network wiring.

A code reader that only reads engine codes may miss important clues stored in other modules.
Inspect the main wiring harness for visible damage. Look for areas where the harness may have been pinched, rubbed through, or exposed to water. Pay attention to connections at the ECM.

The CAN bus wires are typically a twisted pair — a yellow/green or brown/orange pair in most vehicles.
If you recently had electrical work done, check that all connectors are fully seated. A partially connected module connector can cause network communication failures.

This is a common cause after repairs involving the instrument cluster, BCM, or engine control module.
If basic checks do not reveal the cause, take the vehicle to a shop with a manufacturer-specific scan tool. Proper diagnosis of CAN bus faults requires advanced equipment.

Replacing modules without proper diagnosis can be very expensive. Professional diagnosis is worth it here.

When to Call a Professional

P0600 is often complex to diagnose without professional equipment. A shop with a factory-level scan tool can identify exactly which module is failing on the network. Diagnosis typically costs $100 to $200 in labor. Control module replacement ranges from $200 to $1,000 or more depending on the module. ECM replacement may require programming, adding $100 to $300 to the cost.

Frequently Asked Questions

Can I fix P0600 myself?

Basic checks like battery testing and wiring inspection are absolutely worth doing yourself. However, if those do not reveal the problem, professional diagnosis is recommended. CAN bus faults require advanced scan tools and wiring diagrams to diagnose properly.

Why are so many warning lights on with P0600?

All the control modules in your car share a communication network. When that network has a fault, multiple modules stop receiving information. This triggers warning lights for systems those modules control — engine, transmission, ABS, etc.

Will my car start with P0600?

Sometimes yes, sometimes no. If the ECM can still communicate enough to run the engine, the car will start. If the communication fault is severe enough, the car may not start at all. In some cases the car starts but goes into a reduced power mode.