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P1E21 Buick Code - Auxiliary Transmission Fluid Pump Control Module Hybrid/EV Battery Voltage Sense Circuit High Voltage

Quick Answer

The P1E21 diagnostic trouble code (DTC) specifically pertains to the auxiliary transmission fluid pump control module in hybrid and electric vehicles (EVs). Common causes include Faulty wiring or connectors leading to the auxiliary transmission fluid pump control module, A malfunctioning auxiliary transmission fluid pump that is drawing excessive current, Issues with the vehicle's battery or charging system, causing voltage fluctuations. 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
P1E21 Buick indicates Auxiliary Transmission Fluid Pump Control Module Hybrid/EV Battery Voltage Sense Circuit High Voltage.
Common causes
Common causes include Faulty wiring or connectors leading to the auxiliary transmission fluid pump control module, A malfunctioning auxiliary transmission fluid pump that is drawing excessive current, Issues with the vehicle's battery or charging system, causing voltage fluctuations.
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 18, 2024
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Code P1E21 Buick Description

The P1E21 diagnostic trouble code (DTC) specifically pertains to the auxiliary transmission fluid pump control module in hybrid and electric vehicles (EVs). This code indicates that the voltage sensed in the battery circuit associated with the auxiliary transmission fluid pump is higher than the expected threshold. The auxiliary transmission fluid pump is crucial for maintaining optimal fluid pressure in the transmission, especially in hybrid and EV applications where traditional engine-driven pumps may not operate continuously.

OBDII Code P1E21 Buick - Auxiliary Transmission Fluid Pump Control Module Hybrid/EV Battery Voltage Sense Circuit High Voltage
P1E21 Buick Code - Auxiliary Transmission Fluid Pump Control Module Hybrid/EV Battery Voltage Sense Circuit High Voltage

Common Causes of P1E21 Buick

  1. Faulty wiring or connectors leading to the auxiliary transmission fluid pump control module.
  2. A malfunctioning auxiliary transmission fluid pump that is drawing excessive current.
  3. Issues with the vehicle's battery or charging system, causing voltage fluctuations.
  4. A defective control module that misreads voltage levels or fails to regulate them properly.
  5. Corrosion or damage in the voltage sense circuit, leading to inaccurate readings.

Symptoms of P1E21 Buick

  1. Transmission overheating warning lights may illuminate on the dashboard.
  2. Noticeable decrease in transmission performance, such as slipping or delayed engagement.
  3. Unusual noises from the transmission area, indicating potential fluid starvation.
  4. Reduced fuel efficiency due to improper transmission operation.
  5. The vehicle may enter limp mode, restricting speed and power to prevent further damage.

How to Fix P1E21 Buick

  1. Diagnostic Testing: Begin with a thorough diagnostic scan to confirm the P1E21 code and check for any related codes that may provide additional context.
  2. Visual Inspection: Inspect the wiring and connectors associated with the auxiliary transmission fluid pump for any signs of damage, corrosion, or loose connections.
  3. Voltage Testing: Use a multimeter to measure the voltage in the battery sense circuit and compare it to manufacturer specifications to identify any discrepancies.
  4. Component Replacement: If a faulty pump or control module is identified, replace the defective component with a new or refurbished part.
  5. System Reset and Testing: After repairs, clear the DTCs and perform a road test to ensure that the auxiliary transmission fluid pump operates correctly and that the code does not reappear.

Cost to Fix P1E21 Buick

The cost to diagnose and repair the P1E21 code can vary widely based on several factors, including the specific make and model of the vehicle, the location of the repair shop, and the complexity of the issue. On average, the total repair costs can range from $300 to $1,200. This estimate includes parts, which may cost between $100 to $800 depending on whether a new pump or control module is needed, and labor, which typically ranges from $80 to $150 per hour. In metropolitan areas or at dealerships, labor rates may be higher, while independent shops may offer more competitive pricing. It is advisable to consult local repair shops for a more precise estimate tailored to your vehicle's specific needs.

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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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