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Engine-Codes – Generic – C0387

C0387 Code - Unable to Complete Shift

Quick Answer

The C0387 diagnostic trouble code (DTC) indicates that the vehicle's transmission system is unable to complete a shift properly. Common causes include Faulty transmission control module (TCM): The TCM is responsible for controlling the shifting of gears in an automatic transmission, If the TCM malfunctions, it can cause issues with shifting, Low transmission fluid: Insufficient or contaminated transmission fluid can lead to poor lubrication and overheating of transmission components, resulting in shifting problems. 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
C0387 indicates Unable to Complete Shift.
Common causes
Common causes include Faulty transmission control module (TCM): The TCM is responsible for controlling the shifting of gears in an automatic transmission, If the TCM malfunctions, it can cause issues with shifting, Low transmission fluid: Insufficient or contaminated transmission fluid can lead to poor lubrication and overheating of transmission components, resulting in shifting problems.
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 07, 2024
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Code C0387 Description

The C0387 diagnostic trouble code (DTC) indicates that the vehicle's transmission system is unable to complete a shift properly. This can result in issues with the vehicle's ability to change gears smoothly, leading to poor performance, reduced fuel efficiency, and potential safety hazards. When this code is triggered, it typically points to a malfunction in the transmission control module (TCM) or related components.

OBDII Code C0387 - Unable to Complete Shift
C0387 Code - Unable to Complete Shift

Common Causes of C0387

  1. Faulty transmission control module (TCM): The TCM is responsible for controlling the shifting of gears in an automatic transmission. If the TCM malfunctions, it can cause issues with shifting.
  2. Low transmission fluid: Insufficient or contaminated transmission fluid can lead to poor lubrication and overheating of transmission components, resulting in shifting problems.
  3. Transmission solenoid issues: The transmission solenoids control the flow of transmission fluid within the transmission. If a solenoid fails or becomes stuck, it can affect the shifting process.
  4. Faulty shift solenoid: The shift solenoid is responsible for engaging the correct gear during shifting. If the shift solenoid malfunctions, it can cause issues with gear selection.

Symptoms of C0387

  1. Rough or delayed shifting
  2. Slipping gears
  3. Inability to shift into certain gears
  4. Vehicle stuck in a particular gear
  5. Limp mode activation

How to Fix C0387

  1. Diagnose the issue: Use a diagnostic scanner to retrieve the trouble codes and perform a thorough inspection of the transmission system to identify the root cause of the shifting problem.
  2. Check transmission fluid: Ensure the transmission fluid level is correct and that it is not contaminated. If needed, perform a transmission fluid flush and refill.
  3. Test transmission solenoids: Test the transmission solenoids to determine if they are functioning properly. Replace any faulty solenoids as needed.
  4. Inspect and replace TCM: If the TCM is found to be faulty, it will need to be replaced and reprogrammed to ensure proper operation.
  5. Road test: After completing the repairs, road test the vehicle to confirm that the shifting issues have been resolved.

Cost to Fix C0387

The cost of repairing a C0387 code can vary depending on the specific cause of the shifting issue and the labor rates in your area. On average, you can expect to pay between $200 and $800 for parts and labor. Keep in mind that diagnosing and repairing transmission issues can be complex and may require the expertise of a professional mechanic. Be sure to get multiple quotes from reputable auto repair shops to ensure you are getting a fair price for the repair.

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Code C0387 Information for Specific Makes

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 C0387 Code

1. What are the common symptoms of OBDII code C0387 "Unable to Complete Shift"?

- Common symptoms include difficulty shifting gears, the transmission not engaging properly, and the vehicle feeling like it's stuck in a particular gear.

2. What are the possible causes of OBDII code C0387?

- Possible causes can include issues with the transmission control module, faulty shift solenoids, low transmission fluid levels, or a malfunctioning transmission valve body.

3. How can I diagnose the underlying issue causing OBDII code C0387?

- To diagnose the issue, you can perform a thorough inspection of the transmission system, check the transmission fluid level and condition, and use a diagnostic scanner to read the trouble codes and monitor transmission data.

4. Can low transmission fluid cause OBDII code C0387?

- Yes, low transmission fluid levels can lead to OBDII code C0387 as it can cause improper shifting and affect the overall performance of the transmission system.

5. What are some repair tips for fixing OBDII code C0387?

- Repair tips may include checking and topping up transmission fluid levels, inspecting and replacing faulty shift solenoids, ensuring proper connection of transmission control module components, and performing a transmission fluid flush.

6. Is it safe to continue driving with OBDII code C0387 present?

- It is not recommended to continue driving with OBDII code C0387 present, as it can lead to further damage to the transmission system and potentially cause safety hazards on the road.

7. Can a DIY enthusiast fix OBDII code C0387 at home?

- Depending on the root cause of the code, some DIY enthusiasts may be able to fix OBDII code C0387 at home, especially if the issue is related to simple maintenance tasks like checking and refilling transmission fluid.

8. How much does it typically cost to repair OBDII code C0387 at a mechanic or dealership?

- The cost of repairing OBDII code C0387 can vary depending on the specific issue, but it may range from a few hundred to a couple thousand dollars, including parts and labor.

9. Is OBDII code C0387 a common issue in specific vehicle makes or models?

- OBDII code C0387 can occur in various vehicle makes and models, especially those equipped with automatic transmissions, but it may be more prevalent in certain brands or models known for transmission issues.

10. Can resetting the OBDII code C0387 on my vehicle make the issue go away permanently?

- Resetting the OBDII code C0387 may temporarily clear the error code, but if the underlying issue causing the code is not addressed and fixed, it is likely to reoccur. It's important to diagnose and repair the root cause of the problem for a permanent solution.

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