U18B5 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 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.
Code U18B5 Description
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.
What are the Possible Causes of the DTC U18B5?
- 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?
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 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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Information for Specific Makes
- U18B5 Buick — Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus
- U18B5 Cadillac — Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus
- U18B5 Chevrolet — Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus
- U18B5 GMC — Lost Communication With Hybrid Powertrain Control Module On Chassis Expansion CAN Bus
Frequently Asked Questions about U18B5 Code
1. What does the OBDII code U18B5 mean?
U18B5 indicates a loss of communication with the Hybrid Powertrain Control Module (HPCM) on the chassis expansion CAN bus, which is responsible for managing hybrid system operations.
2. What are common symptoms of the U18B5 code?
Symptoms may include warning lights on the dashboard (like the check engine or hybrid system warning light), reduced fuel efficiency, limited hybrid functionality, or the vehicle operating in a reduced power mode.
3. What causes the U18B5 code to appear?
Common causes include faulty wiring or connectors in the CAN bus circuit, a malfunctioning Hybrid Powertrain Control Module, software glitches, or damaged or loose connections within the CAN network.
4. Can the U18B5 code cause drivability issues?
Yes, it can cause issues such as reduced engine power, limited hybrid system operation, or the vehicle entering limp mode to prevent further damage.
5. How can I diagnose the U18B5 code?
Start by inspecting the CAN bus wiring and connectors for damage. Use a scan tool to check for other related codes, and test the Hybrid Powertrain Control Module for proper communication with other modules.
6. Is it safe to drive with the U18B5 code active?
Driving with this code active is not recommended, as it may limit hybrid system performance and lead to further damage or unsafe driving conditions.
7. Can a software update fix the U18B5 code?
In some cases, a software update for the Hybrid Powertrain Control Module or related modules may resolve the issue, especially if the problem is due to a firmware bug.
8. How much does it cost to repair the U18B5 code?
Repair costs vary but may include diagnosing and repairing wiring issues or replacing the Hybrid Powertrain Control Module, which can range from $200 to $1,500 depending on labor and parts.
9. What tools are needed to fix the U18B5 code?
A professional-grade OBDII scan tool with CAN bus diagnostics, a multimeter for testing electrical connections, and access to the vehicle’s wiring diagram are essential for troubleshooting.
10. Can a weak battery cause the U18B5 code?
Yes, a weak or failing 12-volt battery can disrupt communication on the CAN bus, potentially triggering the U18B5 code. Ensure the battery is in good condition before further diagnosis.
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