AutoCodes – Cadillac – U1803 Cadillac

U1803 Cadillac 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 Cadillac 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 436

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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

What does this mean?

What are the Possible Causes of the DTC U1803 Cadillac?

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 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 U1803 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 U1803 Cadillac Code

What does the OBDII code U1803 mean on a Cadillac?

The U1803 code indicates a loss of communication with the Hybrid/EV Powertrain Control Module 2, which is responsible for managing hybrid or electric vehicle systems.

What are the common symptoms of code U1803 in a Cadillac?

Symptoms may include warning lights on the dashboard, reduced power, poor fuel efficiency, the vehicle not starting, or limited hybrid/electric system functionality.

What causes the U1803 code to appear in a Cadillac?

Possible causes include faulty wiring or connectors, a malfunctioning Hybrid/EV Powertrain Control Module 2, issues with the CAN bus system, or a dead or weak 12V battery.

Can driving with the U1803 code damage my Cadillac?

While the car may still function, driving with this code can lead to reduced performance, potential safety issues, and further damage to hybrid or EV components.

How do I diagnose the U1803 code on my Cadillac?

Diagnosis involves checking the wiring and connectors for damage, testing the communication lines in the CAN bus system, and inspecting the Hybrid/EV Powertrain Control Module 2 for faults.

What tools are needed to troubleshoot the U1803 code?

Youâ€™ll need a professional-grade OBDII scanner capable of reading manufacturer-specific codes and a multimeter to test electrical connections.

How can I fix the U1803 code on my Cadillac?

Repairs may include fixing damaged wiring, replacing faulty connectors, reprogramming or replacing the Hybrid/EV Powertrain Control Module 2, or addressing issues in the CAN bus system.

Is a weak 12V battery related to the U1803 code in a Cadillac?

Yes, a weak or dead 12V battery can disrupt communication between modules and trigger the U1803 code.

How much does it cost to repair the U1803 code in a Cadillac?

Repair costs can vary widely, ranging from $100 for minor wiring repairs to over $1,000 if the Hybrid/EV Powertrain Control Module 2 needs replacement.

Can I clear the U1803 code without fixing the problem?

Clearing the code without addressing the root cause may temporarily turn off the warning light, but the issue will likely reoccur and could lead to further damage.