Engine-CodesGeneric – P1787

P1787 Code - Transmission System Third or Fourth Gear Fault

Quick Answer

The P1787 code indicates a fault in the transmission system's third or fourth gear. Common causes include Low transmission fluid levels or dirty fluid, Faulty transmission solenoid, Malfunctioning transmission control module (TCM). 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
P1787 indicates Transmission System Third or Fourth Gear Fault.
Common causes
Common causes include Low transmission fluid levels or dirty fluid, Faulty transmission solenoid, Malfunctioning transmission control module (TCM).
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.
Table of contents Created and updated by William Orellana on Sep 05, 2024
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Code P1787 Description

The P1787 code indicates a fault in the transmission system's third or fourth gear. This fault can lead to issues with shifting, acceleration, and overall performance of the vehicle. When this code is triggered, the transmission may not be able to properly engage third or fourth gear, leading to rough shifting, slipping, or hesitation. This can result in reduced fuel efficiency, loss of power, and potentially damage to the transmission system if left unresolved.

OBDII Code P1787 - Transmission System Third or Fourth Gear Fault
P1787 Code - Transmission System Third or Fourth Gear Fault

Common Causes of P1787

  1. Low transmission fluid levels or dirty fluid
  2. Faulty transmission solenoid
  3. Malfunctioning transmission control module (TCM)
  4. Wiring issues or electrical problems
  5. Mechanical damage to the transmission gears

Symptoms of P1787

  1. Rough or delayed shifting between gears
  2. Slipping or jerking sensation during acceleration
  3. Engine revving without corresponding increase in speed
  4. Transmission overheating
  5. Dashboard warning light illuminated

How to Fix P1787

  1. Check and top up transmission fluid levels
  2. Inspect and replace faulty transmission solenoid
  3. Test and possibly replace the transmission control module
  4. Conduct a thorough inspection of wiring and repair any damaged connections
  5. Repair or replace damaged transmission gears if necessary

Cost to Fix P1787

The cost to repair a transmission system third or fourth gear fault can vary depending on the severity of the issue and the specific components that need to be replaced. On average, this type of repair can range from $500 to $1500, including parts and labor. However, it's important to note that the actual cost can be higher if major components need to be replaced or if the transmission requires extensive repairs. Additionally, labor rates at auto repair shops can vary, so it's recommended to obtain quotes from multiple shops to compare prices.

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Code P1787 Information for Specific Makes

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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