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Engine-Codes – GMC – P0642 2015 GMC Sierra

P0642 2015 GMC Sierra Code - 5 Volt Reference 1 Circuit Low Voltage

Quick Answer

The P0642 diagnostic trouble code (DTC) for a 2015 GMC Sierra indicates that the 5-volt reference circuit 1 is experiencing low voltage. Common causes include Faulty 5-volt reference circuit wiring, Failed 5-volt reference voltage regulator, Short 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 2015 GMC Sierra indicates 5 Volt Reference 1 Circuit Low Voltage.
Common causes
Common causes include Faulty 5-volt reference circuit wiring, Failed 5-volt reference voltage regulator, Short 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 13, 2024
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Code P0642 2015 GMC Sierra Description

The P0642 diagnostic trouble code (DTC) for a 2015 GMC Sierra indicates that the 5-volt reference circuit 1 is experiencing low voltage. This circuit is crucial for providing a stable 5-volt reference signal to various sensors and components throughout the vehicle. When the voltage on this circuit drops below the specified threshold, it can lead to erratic sensor readings, incorrect fuel delivery, and overall poor engine performance.

OBDII Code P0642 2015 GMC Sierra - 5 Volt Reference 1 Circuit Low Voltage
P0642 2015 GMC Sierra Code - 5 Volt Reference 1 Circuit Low Voltage

Common Causes of P0642 2015 GMC Sierra

  1. Faulty 5-volt reference circuit wiring
  2. Failed 5-volt reference voltage regulator
  3. Short circuit in the 5-volt reference circuit
  4. Corrosion or poor connections in the circuit
  5. ECM software or hardware issues

Symptoms of P0642 2015 GMC Sierra

  1. Rough idling or stalling
  2. Poor acceleration or lack of power
  3. Engine misfires
  4. Check Engine Light illuminated
  5. Inaccurate sensor readings

How to Fix P0642 2015 GMC Sierra

  1. Perform a thorough inspection of the 5-volt reference circuit wiring and connectors for any signs of damage or corrosion.
  2. Test the 5-volt reference voltage regulator for proper operation and replace if necessary.
  3. Check for any short circuits in the circuit and repair as needed.
  4. Clear the DTC from the ECM memory and retest the vehicle to ensure the issue has been resolved.
  5. If the problem persists, consider consulting a professional technician for further diagnosis and repair.

Cost to Fix P0642 2015 GMC Sierra

The typical repair costs for addressing a P0642 DTC can vary depending on the specific cause of the issue. In general, the cost of parts such as a voltage regulator or wiring harness can range from $50 to $200, while labor costs can vary between $100 and $300. Overall, the total repair cost for this issue may range from $150 to $500. It's important to note that these are rough estimates, and actual costs may vary based on factors such as location, vehicle make and model, and the extent of the repairs needed. Additionally, diagnostic time and labor rates at auto repair shops can fluctuate, so it's advisable to check with local shops for a more accurate estimate.

What does this mean?

Tech Notes for P0642 2015 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 2015 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 2015 GMC Sierra Code

1. What does the OBDII code P0642 mean on a 2015 GMC Sierra?

P0642 indicates a low voltage issue in the 5-volt reference circuit 1, which supplies power to various engine sensors.

2. What are the common symptoms of code P0642 in a 2015 GMC Sierra?

Symptoms may include poor engine performance, reduced fuel efficiency, erratic sensor readings, and possible activation of the check engine light.

3. What causes the P0642 code to appear in a 2015 GMC Sierra?

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

4. Can I drive my 2015 GMC Sierra with code P0642?

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

5. How do I diagnose the P0642 code on my 2015 GMC Sierra?

Start by inspecting the 5-volt reference wiring and connectors for damage, check for any faulty sensors connected to the circuit, and use a multimeter to verify voltage levels.

6. Which sensors rely on the 5-volt reference circuit in a 2015 GMC Sierra?

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

7. Can a damaged sensor cause the P0642 code on a 2015 GMC Sierra?

Yes, a shorted or faulty sensor connected to the 5-volt reference circuit can cause the voltage to drop and trigger the code.

8. How can I fix the P0642 code on my 2015 GMC Sierra?

Repairs may involve replacing a faulty sensor, repairing damaged wiring or connectors, or in rare cases, replacing the ECM if it is defective.

9. How much does it cost to fix the P0642 code on a 2015 GMC Sierra?

Repair costs vary, but replacing a sensor may cost $100–$300, while more extensive repairs involving wiring or the ECM can exceed $500.

10. Can a faulty ECM cause the P0642 code on a 2015 GMC Sierra?

While rare, a malfunctioning ECM can cause this code if it fails to properly regulate the 5-volt reference circuit.

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