AutoCodes – GMC – P1639 GMC

P1639 GMC Code - PCM 5 Volt Reference Voltage Circuit Condition

Quick Answer

The Powertrain Control Module (PCM) uses the 5-volt reference 2 circuit as a sensor feed for the A/C refrigerant pressure sensor. Common causes include Sensor using 5 volt reference line shorted to ground, Circuit short to ground. 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: P1639 GMC indicates PCM 5 Volt Reference Voltage Circuit Condition.
Common causes: Common causes include Sensor using 5 volt reference line shorted to ground, Circuit short to ground.
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 10,102

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 Sep 04, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1639 GMC Description

The Powertrain Control Module (PCM) uses the 5-volt reference 2 circuit as a sensor feed for the A/C refrigerant pressure sensor. The PCM monitors the voltage on the 5-volt reference 2 circuit.

OBDII Code P1639 GMC - PCM 5 Volt Reference Voltage Circuit Condition - AutoCodes.com — P1639 GMC Code - PCM 5 Volt Reference Voltage Circuit Condition

What does this mean?

What are the Possible Causes of the DTC P1639 GMC?

Sensor using 5 volt reference line shorted to ground
Circuit short to ground

How to Fix the DTC P1639 GMC?

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 P1639 GMC 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.

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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 P1639 GMC Code

1. What are the common symptoms of OBDII code P1639 GMC?

- Common symptoms include engine stalling, rough idling, poor acceleration, and issues with the vehicle's electrical systems.

2. What does the OBDII code P1639 GMC indicate about the PCM 5 volt reference voltage circuit?

- The code indicates a problem with the PCM's ability to regulate the 5-volt reference voltage required for various sensors and components.

3. What are the possible causes of the PCM 5 volt reference voltage circuit condition error?

- Potential causes include a faulty PCM, damaged wiring harness, short circuits, loose connections, or issues with the 5-volt reference voltage regulator.

4. How can I diagnose the PCM 5 volt reference voltage circuit condition error?

- Diagnosis typically involves using a multimeter to check the voltage output of the PCM and inspecting the wiring and connectors for any signs of damage or corrosion.

5. Can driving with the OBDII code P1639 GMC cause further damage to the vehicle?

- Continuing to drive with this code may lead to further electrical issues or damage to the vehicle's sensors and components, so it is advisable to address the problem promptly.

6. How is the PCM 5 volt reference voltage circuit condition error typically repaired?

- Repair may involve replacing the PCM, repairing or replacing damaged wiring, addressing any short circuits, or fixing loose connections as needed.

7. Is it safe to clear the OBDII code P1639 GMC and continue driving the vehicle?

- Clearing the code may temporarily eliminate warning lights, but if the underlying issue is not resolved, it can lead to ongoing problems. It's recommended to diagnose and fix the root cause.

8. Can a DIY enthusiast without advanced automotive knowledge fix the PCM 5 volt reference voltage circuit error?

- While some basic troubleshooting steps can be taken, diagnosing and repairing this issue may require specialized tools and expertise, so it's advisable to seek professional help.

9. Are there any preventive measures to avoid encountering the PCM 5 volt reference voltage circuit condition error?

- Regular vehicle maintenance, including checking the wiring harness for wear and ensuring proper electrical connections, can help prevent issues related to the 5-volt reference voltage circuit.

10. How long does it typically take a mechanic to diagnose and repair the PCM 5 volt reference voltage circuit condition error?

- The time required for diagnosis and repair can vary depending on the specific cause of the issue, but it may take a few hours to a full day for a mechanic to properly address the problem.