Engine-Codes - Generic - U0004

U0004 Code - High Speed CAN Communication Bus (+) Low

- Code Popularity: 11,966 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents

|What are the Possible Causes of the U0004 Code?

  • Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s)
  • Check for more codes
  • Faulty Control Module
  • Control Module harness is open or shorted
  • Control Module circuit poor electrical connection

|How to Fix the U0004 Code?

Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

|What is the cost to diagnose the U0004 code?

Labor: 1.0

The cost to diagnose the U0004 code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

|What are U0004 code possible symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

|What Does the U0004 Code Mean?

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a supervised periodic message that includes the transmitter device availability has not been received.

High Speed CAN Communication Bus (+) Low

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