AutoCodes – GMC – P27AA 2018 GMC Sierra

P27AA 2018 GMC Sierra Code - Transmission Control Solenoid Valve 4 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: P27AA 2018 GMC Sierra indicates Transmission Control Solenoid Valve 4 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 202

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 P27AA 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 P27AA 2018 GMC Sierra - Transmission Control Solenoid Valve 4 Calibration Incorrect - AutoCodes.com — P27AA 2018 GMC Sierra Code - Transmission Control Solenoid Valve 4 Calibration Incorrect

What does this mean?

What are the Possible Causes of the DTC P27AA 2018 GMC Sierra?

Solenoid Valve Characterization Reprogramming

How to Fix the DTC P27AA 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 P27AA 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 P27AA 2018 GMC Sierra 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 P27AA 2018 GMC Sierra Code

1. What does the OBDII code P27AA mean on a 2018 GMC Sierra?

P27AA indicates that the Transmission Control Module (TCM) has detected an issue with the calibration of solenoid valve 4 in the transmission.

2. What are the common symptoms of code P27AA on a 2018 GMC Sierra?

Symptoms may include harsh shifting, delayed gear engagement, transmission slipping, or the check engine light being illuminated.

3. What causes the P27AA code on a GMC Sierra?

This code can be triggered by a faulty transmission solenoid, incorrect solenoid calibration, damaged wiring or connectors, or an issue with the TCM.

4. Can I drive my 2018 GMC Sierra with the P27AA code active?

While the vehicle may still be drivable, driving with this code can lead to further transmission damage. It's best to address the issue promptly.

5. How do you diagnose the P27AA code on a 2018 GMC Sierra?

Diagnosis typically involves scanning the TCM for additional codes, inspecting the solenoid wiring and connectors, and verifying the calibration of the solenoid.

6. How is the P27AA code fixed on a GMC Sierra?

Repairs may include reprogramming or recalibrating the solenoid, replacing a faulty solenoid, repairing damaged wiring, or updating the TCM software.

7. How much does it cost to repair the P27AA code on a 2018 GMC Sierra?

Repair costs vary depending on the issue but can range from $150 for minor wiring repairs to $500 or more for solenoid replacement or TCM reprogramming.

8. Can a transmission fluid issue cause the P27AA code?

Low or contaminated transmission fluid can sometimes contribute to solenoid issues. Checking and maintaining proper fluid levels is essential.

9. Will clearing the P27AA code fix the problem?

Clearing the code without addressing the root cause may temporarily turn off the check engine light, but the issue will likely return until properly repaired.

10. Does the P27AA code require a transmission replacement?

In most cases, a transmission replacement is not necessary. The issue is often resolved by repairing or replacing the affected solenoid or updating the TCM.