AutoCodes – Generic – U1803

U1803 Code - Lost Communication with Hybrid/EV Powertrain Control Module 2

Quick Answer

The serial data circuit is the means by which the devices in the vehicle communicate with each other. Common causes include Faulty Hybrid/EV Powertrain Control Module 2, Hybrid/EV Powertrain Control Module 2 harness is open or shorted, Hybrid/EV Powertrain Control Module 2 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: U1803 indicates Lost Communication with Hybrid/EV Powertrain Control Module 2.
Common causes: Common causes include Faulty Hybrid/EV Powertrain Control Module 2, Hybrid/EV Powertrain Control Module 2 harness is open or shorted, Hybrid/EV Powertrain Control Module 2 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 1,582

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 Jul 21, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1803 Description

The serial data circuit is the means by which the devices in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the Data Link Connector (DLC), the scan tool can be used to monitor each device for diagnostic purposes and to check for Diagnostic Trouble Codes (DTC). When the vehicle is ON, each device communicating on the serial data circuit sends a state of health message to ensure that the device is operating properly. When a device stops communicating on the serial data circuit, for example, if the device loses power or ground, the state of health message it normally sends on the serial data circuit disappears. Other devices on the serial data circuit, which expect to receive that state of health message, detect its absence; those devices in turn set a DTC associated with the loss of state of health of the non-communicating device. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored DTC.

OBDII Code U1803 - Lost Communication with Hybrid/EV Powertrain Control Module 2 - AutoCodes.com — U1803 Code - Lost Communication with Hybrid/EV Powertrain Control Module 2

What does this mean?

What are the Possible Causes of the DTC U1803?

Faulty Hybrid/EV Powertrain Control Module 2
Hybrid/EV Powertrain Control Module 2 harness is open or shorted
Hybrid/EV Powertrain Control Module 2 circuit poor electrical connection

How to Fix the DTC U1803?

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 U1803 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 U1803 code?

Need more information on how to fix the U1803 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1803 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1803 Buick — Lost Communication with Hybrid/EV Powertrain Control Module 2
U1803 Cadillac — Lost Communication with Hybrid/EV Powertrain Control Module 2
U1803 Chevrolet — Lost Communication with Hybrid/EV Powertrain Control Module 2
U1803 GMC — Lost Communication with Hybrid/EV Powertrain Control Module 2

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 U1803 Code

1. What are common symptoms of OBDII code U1803?

- Common symptoms include the hybrid/EV system not functioning properly, loss of power, and dashboard warning lights related to the powertrain.

2. What could cause the OBDII code U1803 to appear?

- The code U1803 typically indicates a communication issue between the vehicle's onboard diagnostics system and the Hybrid/EV Powertrain Control Module 2.

3. How can I diagnose the cause of OBDII code U1803?

- Diagnosing code U1803 requires using a diagnostic scanner to retrieve the code, checking the powertrain communication system for faults, and inspecting the wiring and connectors for any issues.

4. Can a weak battery cause the U1803 code to trigger?

- Yes, a weak or failing battery can sometimes trigger code U1803 due to insufficient power supply affecting communication between modules.

5. What are some repair tips for resolving code U1803?

- Repair tips include checking and repairing any damaged wiring or connectors, ensuring proper battery voltage, and reprogramming or replacing the Hybrid/EV Powertrain Control Module 2 if necessary.

6. Is it safe to continue driving with OBDII code U1803 present?

- It is not recommended to continue driving with code U1803 present, as it may affect the performance and safety of the hybrid/EV system.

7. Can a DIY enthusiast fix OBDII code U1803 at home?

- While some basic troubleshooting like checking connections and fuses can be done at home, diagnosing and repairing code U1803 often requires professional diagnostic tools and expertise.

8. How much does it typically cost to repair OBDII code U1803?

- The cost of repairing code U1803 can vary depending on the underlying cause, but it may involve diagnostic fees, parts replacement, and labor costs, potentially ranging from $100 to $500 or more.

9. Does code U1803 affect the overall drivability of the vehicle?

- Yes, code U1803 can affect the drivability of the vehicle, especially in hybrid or electric vehicles where the powertrain control module plays a crucial role in system operation.

10. Can resetting the OBDII system clear code U1803 permanently?

- Resetting the OBDII system may temporarily clear code U1803, but if the underlying issue causing the communication loss is not resolved, the code is likely to reappear.