AutoCodes – GMC – P0643 2014 GMC Sierra

P0643 2014 GMC Sierra Code - 5 Volt Reference 1 Circuit High Voltage

Quick Answer

The Engine Control Module (ECM) has four (4) internal 5 Volt reference circuits (Some models have two (2) internal 5 Volt reference circuits). Common causes include Faulty Sensor on 5 Volt circuit, Sensor on 5 Volt circuit harness is open or shorted, Sensor on 5 Volt 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: P0643 2014 GMC Sierra indicates 5 Volt Reference 1 Circuit High Voltage.
Common causes: Common causes include Faulty Sensor on 5 Volt circuit, Sensor on 5 Volt circuit harness is open or shorted, Sensor on 5 Volt 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 176

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 17, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0643 2014 GMC Sierra Description

The Engine Control Module (ECM) has four (4) internal 5 Volt reference circuits (Some models have two (2) internal 5 Volt reference circuits). Each internal reference circuit provides external 5 Volt reference circuits for more than one sensor. A short to ground or short to voltage on one external 5 Volt reference circuit can affect all the components connected to the same internal 5 Volt reference circuit. The Diagnostic Trouble Code (DTC) will be set when the ECM detects a higher than the expected voltage on any of the 5 Volt reference circuits for greater than 0.5 s.

OBDII Code P0643 2014 GMC Sierra - 5 Volt Reference 1 Circuit High Voltage - AutoCodes.com — P0643 2014 GMC Sierra Code - 5 Volt Reference 1 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0643 2014 GMC Sierra?

Faulty Sensor on 5 Volt circuit
Sensor on 5 Volt circuit harness is open or shorted
Sensor on 5 Volt circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0643 2014 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 does this mean?

Code Tech Notes

Disconnecting one component at a time from the affected 5 Volt reference circuit while observing the scan tool 5 Volt Reference Circuit Status parameter may help locate the fault. The scan tool parameter will change from Malfunction to OK when the source of the fault is disconnected. If all 5 Volt reference components have been disconnected and a fault is still indicated, the fault may exist in the wiring harness.

The 5 Volt reference 1 circuit provides 5 Volt to the following sensors: (Some models may have different sensors, please consult the factory service manual for the list of sensors for your model and year)

- Air conditioning (A/C) refrigerant pressure sensor
- Camshaft position sensor
- Engine oil pressure sensor
- Fuel pressure sensor
- Fuel rail pressure sensor
- Fuel tank pressure sensor
- Multifunction intake air sensor

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0643 2014 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 P0643 2014 GMC Sierra code?

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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 P0643 2014 GMC Sierra Code

1. What does the OBDII code P0643 mean on a 2014 GMC Sierra?

P0643 indicates a high voltage issue in the 5-volt reference 1 circuit, which supplies a stable voltage to various engine sensors.

2. What are the common symptoms of the P0643 code on a 2014 GMC Sierra?

Symptoms include engine stalling, reduced power mode, poor acceleration, erratic sensor readings, and an illuminated check engine light.

3. What causes the P0643 code to appear on a 2014 GMC Sierra?

Possible causes include a shorted sensor, damaged wiring in the 5-volt reference circuit, a faulty powertrain control module (PCM), or corrosion in the connectors.

4. Can a faulty sensor trigger the P0643 code on a 2014 GMC Sierra?

Yes, if a sensor connected to the 5-volt reference circuit malfunctions or shorts internally, it can cause the circuit voltage to rise and trigger the code.

5. How do I diagnose the P0643 code on a 2014 GMC Sierra?

Start by inspecting the wiring and connectors in the 5-volt reference circuit for damage or corrosion. Use a multimeter to check for proper voltage and isolate any faulty components.

6. Can I drive my 2014 GMC Sierra with a P0643 code?

Driving with this code is not recommended, as it can lead to reduced engine performance or stalling, potentially causing unsafe driving conditions.

7. How is the P0643 code fixed on a 2014 GMC Sierra?

Repairs may include replacing a shorted sensor, repairing or replacing damaged wiring, cleaning corroded connectors, or replacing the PCM if itâ€™s determined to be faulty.

8. How much does it cost to fix the P0643 code on a 2014 GMC Sierra?

Repair costs vary depending on the cause but can range from $100 for a simple wiring repair to over $1,000 if the PCM needs replacement.

9. Can a low battery cause the P0643 code on a 2014 GMC Sierra?

While a low battery is not a direct cause, electrical issues like low voltage or charging system problems can affect the 5-volt reference circuit and trigger the code.

10. How do I prevent the P0643 code from recurring on my 2014 GMC Sierra?

Regularly inspect and maintain the wiring and connectors, ensure sensors are functioning properly, and address any electrical issues promptly to avoid recurring problems.