U1858 GMC Code - Electronic Brake Control Module Lost Communication With Hybrid/EV Powertrain Control Module On Chassis Expansion CAN Bus
Quick Answer
The Drive Motor Control Modules and the Hybrid/EV Powertrain Control Module 1 are all internal to the Power Inverter Module. Common causes include Faulty Hybrid/EV Powertrain Control Module, Hybrid/EV Powertrain Control Module harness is open or shorted, Hybrid/EV 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
- U1858 GMC indicates Electronic Brake Control Module Lost Communication With Hybrid/EV Powertrain Control Module On Chassis Expansion CAN Bus.
- Common causes
- Common causes include Faulty Hybrid/EV Powertrain Control Module, Hybrid/EV Powertrain Control Module harness is open or shorted, Hybrid/EV 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 U1858 GMC Description
Communication diagnostics for the serial data, including device power and ground as well as the wakeup circuits for Drive Motor Control Modules and the Hybrid/EV 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 when a supervised periodic message that includes the transmitter device availability has not been received.
What are the Possible Causes of the DTC U1858 GMC?
- Faulty Hybrid/EV Powertrain Control Module
- Hybrid/EV Powertrain Control Module harness is open or shorted
- Hybrid/EV Powertrain Control Module circuit poor electrical connection
How to Fix the DTC U1858 GMC?
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 U1858 GMC 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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Frequently Asked Questions about U1858 GMC Code
1. What does OBDII code U1858 mean on a GMC?
U1858 indicates that the Electronic Brake Control Module (EBCM) has lost communication with the Hybrid/EV Powertrain Control Module (HPCM) on the Chassis Expansion CAN Bus.
2. What are the common symptoms of a U1858 code on a GMC?
Symptoms may include the ABS or traction control warning light illuminating, reduced braking or traction performance, and possible hybrid/EV system malfunctions.
3. What causes a U1858 code to appear?
Common causes include faulty wiring or connectors in the CAN bus network, a malfunctioning Electronic Brake Control Module, a failing Hybrid/EV Powertrain Control Module, or software issues.
4. Can I drive my GMC with a U1858 code?
It’s not recommended, as it may affect critical systems like braking and traction control, potentially leading to unsafe driving conditions.
5. How do I diagnose a U1858 code on a GMC?
Start by inspecting the CAN bus wiring and connectors for damage or corrosion. Use a scan tool to check for additional codes and monitor communication between modules.
6. What tools are needed to troubleshoot a U1858 code?
You’ll need an OBDII scan tool capable of reading manufacturer-specific codes, a multimeter for testing electrical circuits, and possibly a wiring diagram for the CAN bus.
7. How do I fix a U1858 code on my GMC?
Repairs may include fixing or replacing damaged wiring, cleaning or securing loose connectors, reprogramming or updating module software, or replacing a faulty module.
8. Is the U1858 code specific to GMC hybrid or EV models?
Yes, this code typically applies to GMC vehicles equipped with hybrid or EV powertrains, as it involves communication with the Hybrid/EV Powertrain Control Module.
9. Can a dead battery cause a U1858 code on a GMC?
Yes, a weak or dead 12-volt battery can disrupt communication between modules and trigger this code.
10. How much does it cost to repair a U1858 code on a GMC?
Repair costs can vary widely depending on the cause, ranging from $100 for minor wiring repairs to over $1,000 if module replacement or reprogramming is needed.
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