AutoCodes – GMC – P18E8 GMC

P18E8 GMC Code - Transmission Park Valve Position Sensor 2 Performance

Quick Answer

When the gear selector is in the Park (P) position, fluid is drawn into the pump through the transmission fluid filter assembly, from the transmission fluid pan assembly. Common causes include Low transmission fluid, Faulty Transmission Park Valve, Transmission Park Valve harness is open or shorted. 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: P18E8 GMC indicates Transmission Park Valve Position Sensor 2 Performance.
Common causes: Common causes include Low transmission fluid, Faulty Transmission Park Valve, Transmission Park Valve harness is open or shorted.
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 84

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 Oct 02, 2025

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P18E8 GMC Description

When the gear selector is in the Park (P) position, fluid is drawn into the pump through the transmission fluid filter assembly, from the transmission fluid pan assembly. The Diagnostic Trouble Code (DTC) will set with a hydraulic/mechanical condition.

OBDII Code P18E8 GMC - Transmission Park Valve Position Sensor 2 Performance - AutoCodes.com — P18E8 GMC Code - Transmission Park Valve Position Sensor 2 Performance

What does this mean?

What are the Possible Causes of the DTC P18E8 GMC?

Low transmission fluid
Faulty Transmission Park Valve
Transmission Park Valve harness is open or shorted
Transmission Park Valve circuit poor electrical connection
Faulty Control Valve Solenoid Body

How to Fix the DTC P18E8 GMC?

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 P18E8 GMC 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 P18E8 GMC 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.