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P187D Cadillac Code - Transmission Park Valve Stuck On

Quick Answer

The P187D code indicates that the Transmission Park Valve is stuck in the On position, which can lead to significant issues in the vehicle's transmission system. Common causes include Low transmission fluid levels, leading to inadequate hydraulic pressure, Faulty Transmission Park Valve that fails to operate correctly, Transmission Park Valve harness is open or shorted, disrupting electrical signals. 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
P187D Cadillac indicates Transmission Park Valve Stuck On.
Common causes
Common causes include Low transmission fluid levels, leading to inadequate hydraulic pressure, Faulty Transmission Park Valve that fails to operate correctly, Transmission Park Valve harness is open or shorted, disrupting electrical signals.
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 Oct 02, 2025
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Code P187D Cadillac Description

The P187D code indicates that the Transmission Park Valve is stuck in the On position, which can lead to significant issues in the vehicle's transmission system. The Transmission Park Valve is a critical component that controls the flow of transmission fluid, allowing the vehicle to engage and disengage from the Park position properly. When the gear selector is in Park (P), the valve should allow fluid to be drawn into the pump through the transmission fluid filter assembly from the transmission fluid pan. If the valve is stuck, it can prevent the transmission from properly engaging or disengaging, leading to difficulties in shifting and potential damage to the transmission system.
OBDII Code P187D Cadillac - Transmission Park Valve Stuck On
P187D Cadillac Code - Transmission Park Valve Stuck On

Common Causes of P187D Cadillac

  1. Low transmission fluid levels, leading to inadequate hydraulic pressure
  2. Faulty Transmission Park Valve that fails to operate correctly
  3. Transmission Park Valve harness is open or shorted, disrupting electrical signals
  4. Poor electrical connection in the Transmission Park Valve circuit
  5. Faulty Control Valve Solenoid Body affecting fluid flow and valve operation

Symptoms of P187D Cadillac

  1. Engine Light ON (or Service Engine Soon Warning Light)
  2. Difficulty shifting out of Park (P) position
  3. Unusual noises or grinding sounds when attempting to shift gears
  4. Transmission slipping or erratic behavior during operation
  5. Increased engine RPMs without corresponding acceleration

How to Fix P187D Cadillac

  1. Inspect and top off the transmission fluid to ensure proper levels.
  2. Test the Transmission Park Valve for proper operation and replace if faulty.
  3. Check the Transmission Park Valve harness for any signs of damage or shorts.
  4. Examine the electrical connections in the Transmission Park Valve circuit and repair as necessary.
  5. Inspect the Control Valve Solenoid Body and replace if it is malfunctioning.

Cost to Fix P187D Cadillac

The cost to diagnose and repair the P187D code typically ranges from $300 to $1,200, depending on the specific issues found and the necessary repairs. Labor costs can vary significantly, with most shops charging between $80 and $150 per hour. Dealerships may charge higher rates, while independent shops might offer lower prices. The total cost will also depend on the make and model of the vehicle, as well as the complexity of the repair required.

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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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