AutoCodes – Mercury – B1240 Mercury

B1240 Mercury Code - Start Button Mode Indicator Circuit Short

Quick Answer

The Body Control Module (BCM) uses a Field Effect Transistor (FET) as circuit protection for the start/stop switch indicator and as an electronic switch to turn the start/stop switch indicator on and off. Common causes include Faulty Start/Stop Switch Indicator, Start/Stop Switch Indicator harness is open or shorted, Start/Stop Switch Indicator circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B1240 Mercury indicates Start Button Mode Indicator Circuit Short.
Common causes: Common causes include Faulty Start/Stop Switch Indicator, Start/Stop Switch Indicator harness is open or shorted, Start/Stop Switch Indicator circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 799

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Nov 19, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B1240 Mercury Description

The Body Control Module (BCM) uses a Field Effect Transistor (FET) as circuit protection for the start/stop switch indicator and as an electronic switch to turn the start/stop switch indicator on and off. The FET receives fused battery voltage from BCM. When the start/stop switch is pressed a voltage and ground signal are sent to the BCM. When the vehicle enters RUN or START mode, the BCM forward biases the FET which provides voltage to the amber LED in the start/stop switch, illuminating the word ENGINE.

OBDII Code B1240 Mercury - Start Button Mode Indicator Circuit Short - AutoCodes.com — B1240 Mercury Code - Start Button Mode Indicator Circuit Short

What does this mean?

What are the Possible Causes of the DTC B1240 Mercury?

Faulty Start/Stop Switch Indicator
Start/Stop Switch Indicator harness is open or shorted
Start/Stop Switch Indicator circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B1240 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 does this mean?

Code Tech Notes

B1240:11 Start Button Mode Indicator Circuit Short to Ground
B1240:15 Start Button Mode Indicator Circuit Short to Battery or Open

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B1240 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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Need Help with the 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 B1240 Mercury Code

1. What are the common symptoms of OBDII code B1240 Mercury?

- The common symptoms of code B1240 include a malfunctioning start button mode indicator or a warning light on the dashboard.

2. What can cause the Start Button Mode Indicator Circuit Short in a Mercury vehicle?

- The code B1240 can be caused by a short circuit in the wiring, a faulty start button mode indicator switch, or a defective control module.

3. How can I diagnose the OBDII code B1240 in my Mercury?

- Diagnosing code B1240 involves using a scan tool to retrieve the fault codes and inspecting the start button mode indicator circuit for any visible damage.

4. Can I still drive my Mercury with the B1240 code?

- It is not recommended to drive your Mercury with an active B1240 code, as it may affect the proper operation of the start button mode indicator.

5. Is it easy to repair the Start Button Mode Indicator Circuit Short in a Mercury?

- Repairing the Start Button Mode Indicator Circuit Short may vary in complexity, depending on the exact cause. It is recommended to consult a professional mechanic for proper diagnosis and repair.

6. How much does it typically cost to fix the B1240 code in a Mercury?

- The cost of fixing the B1240 code can vary depending on the cause of the issue, parts needed for replacement, and labor costs. It is advisable to get a few quotes from different repair shops.

7. Are there any DIY tips for repairing the Start Button Mode Indicator Circuit Short?

- DIY repairs for the B1240 code may include checking the wiring connections, inspecting the start button mode indicator switch for damage, and ensuring all related components are functioning properly.

8. Can a faulty battery cause the B1240 code to appear in a Mercury?

- A faulty battery is not a common cause of the B1240 code. However, it is always good practice to ensure the battery is in good condition to prevent any electrical issues in the vehicle.

9. Will resetting the OBDII codes clear the B1240 code in a Mercury?

- Resetting the OBDII codes may temporarily clear the B1240 code, but if the underlying issue is not addressed, the code is likely to reappear. It is essential to diagnose and fix the root cause of the problem.

10. How can I prevent the Start Button Mode Indicator Circuit Short from occurring in my Mercury in the future?

- To prevent the B1240 code from appearing in the future, it is essential to perform regular maintenance checks, avoid electrical overloads, and address any wiring or component issues promptly.