AutoCodes – GMC – P27A8 2018 GMC Sierra

P27A8 2018 GMC Sierra Code - Transmission Control Solenoid Valve 2 Calibration Incorrect

Quick Answer

The Transmission Control Solenoid Valve 1, 2, 3, 4, 5, 6, 7 have a unique current versus oil pressure characteristic that is used to properly upshift or downshift the transmission. Common causes include Solenoid Valve Characterization Reprogramming. 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: P27A8 2018 GMC Sierra indicates Transmission Control Solenoid Valve 2 Calibration Incorrect.
Common causes: Common causes include Solenoid Valve Characterization Reprogramming.
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 173

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 22, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P27A8 2018 GMC Sierra Description

The Transmission Control Solenoid Valve 1, 2, 3, 4, 5, 6, 7 have a unique current versus oil pressure characteristic that is used to properly upshift or downshift the transmission. The data for each solenoid valve is programmed into the Transmission Control Module (TCM). The Diagnostic Trouble Code (DTC) will be set when the Transmission Control Solenoid Valve Calibration Data has not been programmed.

OBDII Code P27A8 2018 GMC Sierra - Transmission Control Solenoid Valve 2 Calibration Incorrect - AutoCodes.com — P27A8 2018 GMC Sierra Code - Transmission Control Solenoid Valve 2 Calibration Incorrect

What does this mean?

What are the Possible Causes of the DTC P27A8 2018 GMC Sierra?

Solenoid Valve Characterization Reprogramming

How to Fix the DTC P27A8 2018 GMC Sierra?

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 P27A8 2018 GMC Sierra 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.

Need more information about the P27A8 2018 GMC Sierra code?

Need more information on how to fix the P27A8 2018 GMC Sierra code? Get Access to Factory Service Manuals

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 P27A8 2018 GMC Sierra Code

1. What does the OBDII code P27A8 on a 2018 GMC Sierra mean?

The code P27A8 indicates "Transmission Control Solenoid Valve 2 Calibration Incorrect," meaning the transmission control module has detected an issue with the calibration of solenoid valve 2.

2. What are the common symptoms of P27A8 in a 2018 GMC Sierra?

Symptoms may include transmission slipping, harsh or erratic shifting, delayed gear engagement, and the illumination of the check engine light.

3. What causes the P27A8 code to appear on a 2018 GMC Sierra?

Common causes include a malfunctioning transmission solenoid, incorrect calibration settings, low or dirty transmission fluid, or a faulty transmission control module (TCM).

4. Can low transmission fluid trigger the P27A8 code?

Yes, low or contaminated transmission fluid can affect solenoid operation and may lead to the P27A8 code being set.

5. Is it safe to drive with the P27A8 code on a 2018 GMC Sierra?

Driving with this code can cause further transmission damage, especially if symptoms like slipping or delayed shifting are present. Itâ€™s best to address the issue promptly.

6. How do you diagnose the P27A8 code on a 2018 GMC Sierra?

Diagnosis typically involves scanning for additional codes, inspecting the transmission fluid, testing the solenoid's electrical connections, and performing a solenoid function test.

7. What repairs are needed to fix the P27A8 code?

Repairs may include replacing the faulty solenoid, updating or reprogramming the TCM, cleaning or replacing the transmission fluid, or repairing wiring issues.

8. Can a software update fix the P27A8 code on a GMC Sierra?

In some cases, a TCM software update or reprogramming may resolve calibration issues and clear the P27A8 code.

9. How much does it cost to fix the P27A8 code on a 2018 GMC Sierra?

Repair costs vary depending on the issue but may range from $200 to $600 for solenoid replacement, with additional charges if a TCM reprogramming is needed.

10. Can I fix the P27A8 code on my GMC Sierra myself?

If you have experience with transmissions, you might handle basic tasks like checking fluid levels or inspecting connections. However, solenoid replacement and TCM programming typically require professional tools and expertise.