AutoCodesCadillac – P18AD Cadillac

P18AD Cadillac Code - Transmission Range Control Valve 2 Position Switch Circuit Stuck Off

Quick Answer

As the vehicle speed increases, the transmission control module (TCM) receives input signals from the automatic transmission input and output speed sensors, throttle position sensor and other vehicle sensors to determine the precise moment to de-energize or “turn off” 1-2-3-4-5-6 solenoid and the solenoid. Common causes include Low transmission fluid, Faulty Transmission Range Control Valve 2 Position Switch, Transmission Range Control Valve 2 Position Switch 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
P18AD Cadillac indicates Transmission Range Control Valve 2 Position Switch Circuit Stuck Off.
Common causes
Common causes include Low transmission fluid, Faulty Transmission Range Control Valve 2 Position Switch, Transmission Range Control Valve 2 Position Switch 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 147
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on Oct 02, 2025
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Code P18AD Cadillac Description

As the vehicle speed increases, the transmission control module (TCM) receives input signals from the automatic transmission input and output speed sensors, throttle position sensor and other vehicle sensors to determine the precise moment to de-energize or “turn off” 1-2-3-4-5-6 solenoid and the solenoid. The Diagnostic Trouble Code (DTC) will set with a hydraulic/mechanical condition.
OBDII Code P18AD Cadillac - Transmission Range Control Valve 2 Position Switch Circuit Stuck Off - AutoCodes.com
P18AD Cadillac Code - Transmission Range Control Valve 2 Position Switch Circuit Stuck Off

What are the Possible Causes of the DTC P18AD Cadillac?

  • Low transmission fluid
  • Faulty Transmission Range Control Valve 2 Position Switch
  • Transmission Range Control Valve 2 Position Switch harness is open or shorted
  • Transmission Range Control Valve 2 Position Switch circuit poor electrical connection
  • Faulty Control Valve Solenoid Body

How to Fix the DTC P18AD Cadillac?

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 P18AD Cadillac 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 P18AD Cadillac 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.

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