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Engine-Codes – GMC – P0642 GMC

P0642 GMC Code - 5 Volt Reference 1 Circuit Low Voltage

Quick Answer

The P0642 GMC code indicates that the 5 Volt Reference 1 Circuit is experiencing low voltage. Common causes include Damaged wiring or connectors in the 5 Volt Reference 1 Circuit, A faulty Engine Control Module (ECM), Defective sensor or component drawing excessive current. 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
P0642 GMC indicates 5 Volt Reference 1 Circuit Low Voltage.
Common causes
Common causes include Damaged wiring or connectors in the 5 Volt Reference 1 Circuit, A faulty Engine Control Module (ECM), Defective sensor or component drawing excessive current.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 09, 2024
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Code P0642 GMC Description

The P0642 GMC code indicates that the 5 Volt Reference 1 Circuit is experiencing low voltage. In modern vehicles, many sensors and components rely on a stable 5-volt reference voltage supplied by the Engine Control Module (ECM) to operate correctly. When this reference voltage drops below a certain threshold, it can lead to various issues within the vehicle's systems.

OBDII Code P0642 GMC - 5 Volt Reference 1 Circuit Low Voltage
P0642 GMC Code - 5 Volt Reference 1 Circuit Low Voltage

Common Causes of P0642 GMC

  1. Damaged wiring or connectors in the 5 Volt Reference 1 Circuit
  2. A faulty Engine Control Module (ECM)
  3. Defective sensor or component drawing excessive current
  4. Short circuit in the circuit
  5. Corrosion or poor connections in the circuit

Symptoms of P0642 GMC

  1. Check Engine Light illuminated on the dashboard
  2. Engine performance issues such as rough idling or stalling
  3. Hesitation or lack of power during acceleration
  4. Inability to start the vehicle
  5. Erratic behavior from sensors and components

How to Fix P0642 GMC

  1. Use a diagnostic scanner to retrieve the fault code and freeze frame data for further analysis.
  2. Inspect the wiring and connectors in the 5 Volt Reference 1 Circuit for any damage or corrosion. Repair or replace as needed.
  3. Test the sensors and components connected to the circuit to identify any faulty units. Replace as necessary.
  4. Check for any short circuits in the circuit and repair them accordingly.
  5. Clear the fault code and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0642 GMC

The typical repair costs for addressing the P0642 GMC code can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, you can expect to pay anywhere from $100 to $500 for parts and labor to resolve this issue. It's important to note that diagnosis time and labor rates at auto repair shops can vary, so it's advisable to check with local shops for a more precise estimate based on your vehicle make and model. Additionally, rates at dealerships or in metropolitan areas may be higher, while independent shops often charge less for repairs.

What does this mean?

Tech Notes for P0642 GMC

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

Need more information about the P0642 GMC code?

Need more information on how to fix the P0642 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0642 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

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 P0642 GMC Code

1. What are the common symptoms of OBDII code P0642 GMC?

- Common symptoms include issues with engine performance, rough idling, stalling, and the illumination of the Check Engine Light.

2. What does the OBDII code P0642 GMC "5 Volt Reference 1 Circuit Low Voltage" mean?

- This code indicates that the voltage on the 5-volt reference circuit 1 is lower than expected.

3. What are the potential causes of OBDII code P0642 GMC?

- Possible causes include a faulty engine control module (ECM), damaged wiring or connectors in the 5-volt reference circuit, or a short circuit to ground.

4. How can I diagnose the issue related to OBDII code P0642 GMC?

- Diagnosing this code typically involves checking the voltage on the 5-volt reference circuit, inspecting the wiring and connectors, and testing the ECM for proper function.

5. Can I continue driving my vehicle with OBDII code P0642 GMC present?

- It is not recommended to drive the vehicle with this code present, as it can lead to further damage or engine performance issues.

6. How serious is OBDII code P0642 GMC?

- While the seriousness of the code can vary, it is important to address it promptly to prevent potential damage to the engine or other components.

7. How can I repair OBDII code P0642 GMC?

- Repairing this code may involve replacing the ECM, repairing damaged wiring or connectors, or addressing any short circuits to ground in the 5-volt reference circuit.

8. Can I reset the Check Engine Light after fixing OBDII code P0642 GMC?

- Yes, once the underlying issue causing the code is repaired, the Check Engine Light can be reset using an OBDII scanner.

9. Is it necessary to consult a mechanic for OBDII code P0642 GMC?

- While some DIY enthusiasts may be able to diagnose and repair this code, it is recommended to consult a mechanic for accurate diagnosis and proper repair.

10. How much does it cost to fix OBDII code P0642 GMC?

- The cost of fixing this code can vary depending on the specific issue causing it, but it may involve parts and labor costs ranging from $100 to $500 or more.

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