AutoCodes – Mercury – P0642 Mercury

P0642 Mercury Code - Sensor Reference Voltage 'A' Circuit Low

Quick Answer

The control module has 2 internal 5-volt reference buses called "5-volt reference 1" and"5-volt reference 2". Common causes include Faulty Engine Control Module (ECM), ECM harness is open or shorted, ECM 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: P0642 Mercury indicates Sensor Reference Voltage 'A' Circuit Low.
Common causes: Common causes include Faulty Engine Control Module (ECM), ECM harness is open or shorted, ECM 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 2,022

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 May 01, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0642 Mercury Description

The control module has 2 internal 5-volt reference buses called "5-volt reference 1" and"5-volt reference 2". Each reference bus provided 5-volt reference circuit for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to the reference bus. The control module monitors the voltage on the 5-volt reference buses.

OBDII Code P0642 Mercury - Sensor Reference Voltage 'A' Circuit Low - AutoCodes.com — P0642 Mercury Code - Sensor Reference Voltage 'A' Circuit Low

What does this mean?

What are the Possible Causes of the DTC P0642 Mercury?

Faulty Engine Control Module (ECM)
ECM harness is open or shorted
ECM circuit poor electrical connection
Shorted sensor on 5 volt circuit

How to Fix the DTC P0642 Mercury?

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 P0642 Mercury 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 P0642 Mercury Code

1. What are the common symptoms of OBDII code P0642 in a Mercury vehicle?

- Common symptoms include issues with engine performance, rough idling, stalling, and illuminated Check Engine light.

2. What does the OBDII code P0642 for Sensor Reference Voltage 'A' Circuit Low indicate in a Mercury vehicle?

- This code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the Sensor Reference Voltage 'A' circuit.

3. What are the potential causes of the Sensor Reference Voltage 'A' Circuit Low code in a Mercury?

- Possible causes include a faulty sensor, damaged wiring or connectors, a malfunctioning PCM, or a short circuit in the reference voltage circuit.

4. How can I diagnose the OBDII code P0642 in my Mercury to pinpoint the issue?

- Diagnosing this code typically involves using a multimeter to test the reference voltage circuit, checking the sensor connections, and inspecting the wiring for any damage.

5. Is it safe to continue driving my Mercury with the P0642 trouble code present?

- It is not recommended to continue driving with this code as it can lead to potential engine performance issues and further damage if left unresolved.

6. Can I repair the Sensor Reference Voltage 'A' Circuit Low issue in my Mercury myself?

- Depending on your automotive repair skills, you may be able to address this issue yourself by identifying and fixing the root cause, such as replacing a faulty sensor or repairing wiring.

7. Will resetting the OBDII code P0642 in my Mercury make it go away permanently?

- Simply resetting the code may temporarily turn off the Check Engine light, but if the underlying issue is not fixed, the code is likely to reappear.

8. How much does it typically cost to repair the Sensor Reference Voltage 'A' Circuit Low problem in a Mercury at a repair shop?

- The cost of repair can vary depending on the specific cause of the issue, but it may involve parts replacement, labor costs, and diagnostic fees, ranging from $100 to $500 or more.

9. Can a faulty battery or alternator cause the P0642 code to trigger in a Mercury?

- Yes, a weak or failing battery or alternator can sometimes lead to voltage irregularities that trigger the Sensor Reference Voltage 'A' Circuit Low code.

10. Are there any preventive measures I can take to avoid encountering the P0642 trouble code in my Mercury?

- Regular vehicle maintenance, including checking the electrical system components and sensors, can help prevent issues like the Sensor Reference Voltage 'A' Circuit Low code from occurring.