AutoCodes – GMC – P1003 2018 GMC Sierra

P1003 2018 GMC Sierra Code - Fuel Composition Signals Message Counter Incorrect

Quick Answer

Control modules connected to the serial data circuits monitor the communication during normal vehicle operation. Common causes include Faulty Fuel Composition Sensor, Fuel Composition Sensor harness is open or shorted, Fuel Composition Sensor 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: P1003 2018 GMC Sierra indicates Fuel Composition Signals Message Counter Incorrect.
Common causes: Common causes include Faulty Fuel Composition Sensor, Fuel Composition Sensor harness is open or shorted, Fuel Composition Sensor 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 191

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 Aug 18, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1003 2018 GMC Sierra Description

Control modules connected to the serial data circuits monitor the communication during normal vehicle operation. Operating information and commands are exchanged among the control modules. Each module on the serial data circuit maintains a transmit error counter and a receive error counter. The counter values increase with detected errors and decrease with error-free messages. The Diagnostic Trouble Code (DTC) will be set when the Fuel Composition Signals Message Counter Incorrect.

OBDII Code P1003 2018 GMC Sierra - Fuel Composition Signals Message Counter Incorrect - AutoCodes.com — P1003 2018 GMC Sierra Code - Fuel Composition Signals Message Counter Incorrect

What does this mean?

What are the Possible Causes of the DTC P1003 2018 GMC Sierra?

Faulty Fuel Composition Sensor
Fuel Composition Sensor harness is open or shorted
Fuel Composition Sensor circuit poor electrical connection

How to Fix the DTC P1003 2018 GMC Sierra?

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 P1003 2018 GMC Sierra 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 P1003 2018 GMC Sierra code?

Need more information on how to fix the P1003 2018 GMC Sierra code? Get Access to Factory Service Manuals

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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 P1003 2018 GMC Sierra Code

1. What does the OBDII code P1003 mean on a 2018 GMC Sierra?

P1003 indicates that the Fuel Composition Signal Message Counter is incorrect, meaning there is an issue with how the fuel composition data is being communicated to the engine control module (ECM).

2. What are the common symptoms of code P1003 in a 2018 GMC Sierra?

Symptoms may include poor engine performance, reduced fuel efficiency, hesitation during acceleration, or the check engine light being illuminated.

3. What causes the P1003 code to appear on a 2018 GMC Sierra?

Possible causes include a faulty fuel composition sensor, wiring or connection issues in the fuel composition circuit, or a malfunctioning engine control module (ECM).

4. Can I drive my 2018 GMC Sierra with the P1003 code active?

Driving with this code is generally not recommended as it can lead to reduced performance, higher emissions, and potential long-term engine damage if not addressed.

5. How do I fix the P1003 code on my 2018 GMC Sierra?

Repairs may include inspecting and repairing wiring or connectors in the fuel composition circuit, replacing the fuel composition sensor, or updating/reprogramming the ECM if necessary.

6. How do I diagnose the P1003 code on a 2018 GMC Sierra?

Diagnosis typically involves using an OBDII scanner to confirm the code, checking the fuel composition sensor and its wiring for damage, and testing the ECM for proper communication.

7. What is the fuel composition sensor in a 2018 GMC Sierra?

The fuel composition sensor measures the ethanol content in the fuel and sends this data to the ECM to ensure optimal engine performance.

8. Will clearing the code P1003 solve the problem on a 2018 GMC Sierra?

Clearing the code without addressing the underlying issue will not fix the problem, and the code is likely to reappear.

9. Is the fuel composition sensor expensive to replace on a 2018 GMC Sierra?

The cost of replacing a fuel composition sensor can vary depending on labor rates and parts availability but is generally considered a moderate repair cost.

10. Can a software update fix the P1003 code on a 2018 GMC Sierra?

In some cases, a software update or reprogramming the ECM may resolve the issue if it is related to incorrect communication protocols. A professional diagnosis is recommended to confirm.