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P1EC5 Buick Code - Hybrid/EV Battery Pack Heater Transistor Stuck On

Quick Answer

The hybrid/EV battery contains 5 high voltage contactors and 2 transistors. Common causes include Faulty Battery Energy Control Module, Battery Energy Control Module harness is open or shorted, Battery Energy Control Module circuit poor electrical connection. 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
P1EC5 Buick indicates Hybrid/EV Battery Pack Heater Transistor Stuck On.
Common causes
Common causes include Faulty Battery Energy Control Module, Battery Energy Control Module harness is open or shorted, Battery Energy Control Module circuit poor electrical connection.
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 942
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Apr 25, 2020
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Code P1EC5 Buick Description

The hybrid/EV battery contains 5 high voltage contactors and 2 transistors. The high voltage contactors and transistors allow the high voltage DC batteries to be connected to the vehicle or safely contain the high voltage DC within the hybrid/EV battery assembly. The 5 high voltage contactors consist of a main positive high voltage contactor, main negative high voltage contactor, charge positive high voltage contactor, charge negative high voltage contactor and multi-function high voltage contactor. The 2 transistors consist of the precharge transistor and heater transistor. The contactors and transistors close and open in a specific sequence controlled by the hybrid/EV powertrain control module 2. The hybrid/EV powertrain control module 2 supplies voltage to the control circuit for the high voltage contactors/transistors. Ground is provided through the case ground.
OBDII Code P1EC5 Buick - Hybrid/EV Battery Pack Heater Transistor Stuck On - AutoCodes.com
P1EC5 Buick Code - Hybrid/EV Battery Pack Heater Transistor Stuck On
What does this mean?

What are the Possible Causes of the DTC P1EC5 Buick?

  • Faulty Battery Energy Control Module
  • Battery Energy Control Module harness is open or shorted
  • Battery Energy Control Module circuit poor electrical connection

How to Fix the DTC P1EC5 Buick?

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 P1EC5 Buick 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 P1EC5 Buick code?

Need more information on how to fix the P1EC5 Buick code? Get Access to Factory Service Manuals

Need Help with the 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.

Frequently Asked Questions about P1EC5 Buick Code

1. What does the OBDII code P1EC5 mean on a Buick?

This code indicates that the Hybrid/EV Battery Pack Heater Transistor is stuck in the "on" position, preventing proper regulation of the battery pack heater.

2. What are the common symptoms of code P1EC5 in a Buick?

Symptoms may include the check engine light or hybrid system warning light turning on, decreased fuel efficiency, or issues with the hybrid/EV battery heating system.

3. What causes the P1EC5 code to appear?

The code is typically caused by a malfunctioning battery pack heater transistor, a short circuit in the wiring, or a faulty battery pack heater control module.

4. Can I drive my Buick with the P1EC5 code?

While the vehicle may still be drivable, ignoring this code could lead to reduced battery efficiency or damage to the hybrid system, so it's best to address it promptly.

5. How is the P1EC5 code diagnosed?

A technician will use a scan tool to verify the code, inspect the battery pack heater circuit, and check for any damaged wiring or components.

6. What repairs can fix the P1EC5 code?

Common repairs include replacing the faulty battery pack heater transistor, fixing damaged wiring, or replacing the battery heater control module.

7. How much does it cost to repair code P1EC5 on a Buick?

The repair cost can vary, but it typically ranges from $200 to $600, depending on the part that needs replacement and labor costs.

8. Can a dead hybrid battery cause the P1EC5 code?

No, this code specifically relates to the heater transistor, not the battery pack itself, though battery performance may be indirectly affected.

9. Will resetting the code fix the P1EC5 issue?

Resetting the code may temporarily clear the warning, but the issue will likely recur unless the underlying problem is resolved.

10. How can I prevent the P1EC5 code from returning?

Regular maintenance, inspecting hybrid system components, and ensuring proper electrical connections can help prevent the code from reappearing.

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