AutoCodes – Generic – U0027

U0027 Code - Low Speed CAN Communication Bus (-) Shorted To Bus (+)

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: U0027 indicates Low Speed CAN Communication Bus (-) Shorted To Bus (+).
Common causes: Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 4,464

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 29, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0027 Description

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.

OBDII Code U0027 - Low Speed CAN Communication Bus (-) Shorted To Bus (+) - AutoCodes.com — U0027 Code - Low Speed CAN Communication Bus (-) Shorted To Bus (+)

What does this mean?

What are the Possible Causes of the DTC U0027?

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 DTC U0027?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0027 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the U0027 code?

Need more information on how to fix the U0027 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0027 code diagnosed by a professional: Find a repair shop in your area

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about U0027 Code

1. What does the OBDII code U0027 mean?

- The code U0027 indicates that there is a problem with the low-speed Controller Area Network (CAN) communication bus, specifically that the negative side of the bus is shorted to the positive side.

2. What are the common symptoms of code U0027?

- Symptoms can include the malfunction indicator lamp (MIL) turning on, various electrical issues, possible transmission shifting problems, decreased fuel efficiency, or the vehicle entering a limp mode.

3. What can cause the U0027 code to appear?

- Causes include damaged wiring, faulty connectors, issues with the CAN bus network devices (like ECUs or sensors), or a short circuit within the network.

4. How do I diagnose the problem leading to code U0027?

- Diagnosis should start with a visual inspection of the CAN bus wiring and connectors for damage or corrosion. Use a multimeter to check for continuity and short circuits. A scan tool can be very helpful to monitor live CAN bus data.

5. What steps should I take to fix the U0027 code?

- Repair or replace any damaged wires or connectors. If the wiring and connectors are fine, further testing of the CAN bus devices and replacing any faulty components may be necessary.

6. Is it safe to drive with the U0027 code?

- Driving with this code is not recommended as it can affect the functionality of various systems in the vehicle, potentially leading to safety issues.

7. Can U0027 affect the vehicle's performance?

- Yes, this code can affect vehicle performance by impacting the communication between different electronic control units, which can alter or inhibit normal vehicle operations.

8. What tools are needed to diagnose the U0027 code?

- Tools needed include a digital multimeter, a professional scan tool capable of interpreting CAN bus data, and possibly an oscilloscope for more detailed electrical analysis.

9. Could ignoring the U0027 code lead to other problems?

- Ignoring this code can lead to further damage to the electrical system and possibly cause other critical systems in the vehicle to fail, potentially resulting in expensive repairs.

10. How often does the U0027 code occur in vehicles?

- The frequency of U0027 occurring is not common and usually points towards specific issues in the vehicleâ€™s CAN bus communication system, typically influenced by vehicle condition, maintenance history, and external damage to wiring.