AutoCodes – Cadillac – U18B5 Cadillac

U18B5 Cadillac Code - Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus

Quick Answer

Devices connected to the Chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Hybrid Powertrain Control Module, Hybrid Powertrain Control Module harness is open or shorted, Hybrid Powertrain Control Module circuit poor electrical connection. 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: U18B5 Cadillac indicates Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus.
Common causes: Common causes include Faulty Hybrid Powertrain Control Module, Hybrid Powertrain Control Module harness is open or shorted, Hybrid Powertrain Control Module circuit poor electrical connection.
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 497

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 Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18B5 Cadillac Description

Devices connected to the Chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device.
The Motor Control Modules and the Hybrid Powertrain Control Module 1 are all internal to the Power Inverter Module. Communication diagnostics for the serial data, including device power and ground as well as the wakeup circuits for Motor Control Modules and the Hybrid Powertrain Control Module 1 are all diagnosed from external sources only to the Power Inverter Module connector because any circuit fault condition within the Power Inverter Module will cause a complete replacement.The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18B5 Cadillac - Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus - AutoCodes.com — U18B5 Cadillac Code - Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18B5 Cadillac?

Faulty Hybrid Powertrain Control Module
Hybrid Powertrain Control Module harness is open or shorted
Hybrid Powertrain Control Module circuit poor electrical connection

How to Fix the DTC U18B5 Cadillac?

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 U18B5 Cadillac 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.

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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 U18B5 Cadillac Code

1. What are the common symptoms of OBDII code U18B5 in a Cadillac related to lost communication with the hybrid powertrain control module on the chassis expansion CAN bus?

The common symptoms include the hybrid system not engaging, poor fuel efficiency, loss of power, and potential stalling.

2. What are the possible causes of OBDII code U18B5 in a Cadillac?

Possible causes include wiring issues, faulty hybrid powertrain control module, communication network issues, or a malfunctioning CAN bus.

3. How can I diagnose the source of the communication problem with the hybrid powertrain control module on the chassis expansion CAN bus in a Cadillac?

You can use a diagnostic scanner to retrieve the specific trouble codes, check the wiring connections for any damage, inspect the hybrid powertrain control module for faults, and test the CAN bus for proper functionality.

4. Can I repair OBDII code U18B5 in a Cadillac on my own?

Repairing this code may require advanced diagnostic tools and expertise, so it is recommended to consult a professional mechanic with experience in hybrid vehicle systems.

5. Are there any specific maintenance tips to prevent OBDII code U18B5 from occurring in a Cadillac?

Regularly inspecting the wiring harness, keeping the hybrid powertrain control module updated with the latest software, and ensuring proper system maintenance can help prevent communication issues.

6. Is it safe to continue driving a Cadillac with OBDII code U18B5 related to lost communication with the hybrid powertrain control module?

It is not recommended to continue driving the vehicle with this code present, as it may lead to further damage to the hybrid system and potentially unsafe driving conditions.

7. How much does it typically cost to repair OBDII code U18B5 in a Cadillac?

The cost of repair can vary depending on the exact cause of the communication issue, but it may involve replacing wiring components, the hybrid powertrain control module, or addressing CAN bus problems, which can range from a few hundred to over a thousand dollars.

8. Will resetting the OBDII code U18B5 in a Cadillac make the problem go away permanently?

Simply resetting the code without addressing the underlying communication issue will not fix the problem permanently. It is important to diagnose and repair the root cause to prevent the code from reoccurring.

9. Can extreme weather conditions affect the occurrence of OBDII code U18B5 in a Cadillac?

Extreme temperatures or weather conditions can potentially impact the electrical connections and components involved in the hybrid system, leading to communication failures and triggering the U18B5 trouble code.

10. How long does it typically take to repair OBDII code U18B5 in a Cadillac?

The repair time can vary depending on the complexity of the issue and the availability of parts. It may range from a few hours to a full day or more, especially if extensive diagnostic work is required.