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Engine-Codes – GMC – P0642 2017 GMC Sierra

P0642 2017 GMC Sierra Code - 5 Volt Reference 1 Circuit Low Voltage

Quick Answer

The P0642 diagnostic trouble code (DTC) for the 2017 GMC Sierra indicates a problem with the 5 Volt Reference 1 Circuit, specifically a low voltage issue. Common causes include Faulty 5 Volt Reference circuit wiring or connections, Defective Engine Control Module (ECM), Short circuit or open circuit in the 5 Volt Reference circuit. 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 2017 GMC Sierra indicates 5 Volt Reference 1 Circuit Low Voltage.
Common causes
Common causes include Faulty 5 Volt Reference circuit wiring or connections, Defective Engine Control Module (ECM), Short circuit or open circuit in the 5 Volt Reference circuit.
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 15, 2024
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Code P0642 2017 GMC Sierra Description

The P0642 diagnostic trouble code (DTC) for the 2017 GMC Sierra indicates a problem with the 5 Volt Reference 1 Circuit, specifically a low voltage issue. The 5 Volt Reference circuit is a critical component in the vehicle's electronic control system, providing a stable 5-volt power supply to various sensors and components throughout the vehicle. When the voltage on this circuit drops below the specified range, it can lead to malfunctions in the vehicle's systems and affect its overall performance.

OBDII Code P0642 2017 GMC Sierra - 5 Volt Reference 1 Circuit Low Voltage
P0642 2017 GMC Sierra Code - 5 Volt Reference 1 Circuit Low Voltage

Common Causes of P0642 2017 GMC Sierra

  1. Faulty 5 Volt Reference circuit wiring or connections
  2. Defective Engine Control Module (ECM)
  3. Short circuit or open circuit in the 5 Volt Reference circuit
  4. Failed sensor or component drawing excessive current
  5. Corrosion or damage to the wiring harness

Symptoms of P0642 2017 GMC Sierra

  1. Check Engine Light illuminated on the dashboard
  2. Engine misfires or rough idling
  3. Reduced engine power or acceleration
  4. Poor fuel economy
  5. Difficulty starting the vehicle

How to Fix P0642 2017 GMC Sierra

  1. Begin by using a diagnostic scanner to retrieve the trouble codes and verify the P0642 code.
  2. Inspect the wiring and connections related to the 5 Volt Reference 1 Circuit for any signs of damage, corrosion, or loose connections.
  3. Test the voltage output of the circuit using a multimeter to determine if it falls below the specified range.
  4. Replace any faulty sensors or components that may be causing excessive current draw on the 5 Volt Reference circuit.
  5. If necessary, replace the Engine Control Module (ECM) if it is determined to be the source of the low voltage condition.

Cost to Fix P0642 2017 GMC Sierra

The typical repair costs for addressing a P0642 code on a 2017 GMC Sierra can vary depending on the specific cause of the issue. On average, the parts required for this repair may range from $50 to $200, while labor costs can range from $100 to $300. However, it is essential to note that the actual costs can fluctuate based on factors such as the location of the repair, the dealership or independent shop rates, and the extent of the repairs needed. It is advisable to consult with a qualified mechanic or repair shop to obtain a more accurate estimate based on the specific circumstances of the vehicle.

What does this mean?

Tech Notes for P0642 2017 GMC Sierra

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 2017 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 P0642 2017 GMC Sierra Code

1. What does OBDII code P0642 mean on a 2017 GMC Sierra?

Code P0642 indicates a low voltage condition in the 5-volt reference circuit 1, which is critical for proper sensor operation.

2. What are the common symptoms of code P0642 in a 2017 GMC Sierra?

Symptoms may include poor engine performance, erratic sensor readings, illuminated check engine light, and potential issues with transmission shifting or reduced power mode.

3. What causes the P0642 code in a 2017 GMC Sierra?

Common causes include a shorted or damaged sensor, wiring issues such as frayed or corroded wires, or a malfunctioning powertrain control module (PCM).

4. Can a faulty sensor trigger the P0642 code?

Yes, a shorted sensor on the 5-volt reference circuit can pull the voltage down and trigger this code.

5. How can I diagnose the P0642 code in my 2017 GMC Sierra?

Inspect the 5-volt reference circuit wiring for damage, test the sensors on the circuit for shorts, and measure the voltage at the PCM and sensors using a multimeter.

6. Is it safe to drive with the P0642 code on a 2017 GMC Sierra?

Driving with this code is not recommended as it can lead to erratic engine performance and potential damage to other components.

7. How do I fix the P0642 code on a 2017 GMC Sierra?

Repairs may involve replacing a shorted sensor, repairing damaged wiring, or, in rare cases, replacing the PCM if it’s determined to be faulty.

8. Which sensors are connected to the 5-volt reference circuit in the 2017 GMC Sierra?

Sensors such as the throttle position sensor (TPS), manifold absolute pressure (MAP) sensor, and others may share the 5-volt reference circuit.

9. Can a bad PCM cause the P0642 code?

While rare, a faulty PCM can cause the P0642 code if it fails to regulate the 5-volt reference signal properly.

10. How much does it cost to fix a P0642 code on a 2017 GMC Sierra?

Repair costs can vary widely, from $50 to $150 for a damaged sensor or wiring repair, to over $500 if the PCM needs replacement and reprogramming.

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