AutoCodes – Cadillac – P0C28 Cadillac

P0C28 Cadillac Code - Auxiliary Transmission Fluid Pump High Current

Quick Answer

The power inverter module, often referred to as the drive motor generator power inverter module, contains two motor control modules and the hybrid/EV powertrain control module 1. Common causes include Faulty Transmission Fluid Pump Electric/Auxiliary, Transmission Fluid Pump Electric/Auxiliary harness is open or shorted, Transmission Fluid Pump Electric/Auxiliary 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: P0C28 Cadillac indicates Auxiliary Transmission Fluid Pump High Current.
Common causes: Common causes include Faulty Transmission Fluid Pump Electric/Auxiliary, Transmission Fluid Pump Electric/Auxiliary harness is open or shorted, Transmission Fluid Pump Electric/Auxiliary 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 27

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Nov 05, 2025

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0C28 Cadillac Description

The power inverter module, often referred to as the drive motor generator power inverter module, contains two motor control modules and the hybrid/EV powertrain control module 1. The motor control modules operate their respective drive motor based upon power inverter module commands. The hybrid/EV powertrain control module 1 controls the auxiliary transmission fluid pump. The motors utilize 3 phase AC electricity. The motor stator coil is comprised of three phase circuits. The phase circuits are identified as phase U, phase V, and phase W. The U-V-W phase circuits are connected in a wye configuration. This means each phase is connected at a single, central point. The motor control modules monitor a current sensor connected to each motor phase. The current sensor is part of the power inverter module and is not serviced separately. The hybrid/EV powertrain control module 1 is part of the power inverter module and are not serviced separately.

OBDII Code P0C28 Cadillac - Auxiliary Transmission Fluid Pump High Current - AutoCodes.com — P0C28 Cadillac Code - Auxiliary Transmission Fluid Pump High Current

What does this mean?

What are the Possible Causes of the DTC P0C28 Cadillac?

Faulty Transmission Fluid Pump Electric/Auxiliary
Transmission Fluid Pump Electric/Auxiliary harness is open or shorted
Transmission Fluid Pump Electric/Auxiliary circuit poor electrical connection
Faulty Power Inverter Module

How to Fix the DTC P0C28 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 P0C28 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.

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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.