What is OBD-II Code P028E – Charge Air Cooler Cooling Fan Control Circuit High

What is OBD-II Code P028E – Charge Air Cooler Cooling Fan Control Circuit High: A Mechanic’s Guide to Understanding and Troubleshooting

As a mechanic, I have come across several OBD-II codes over the years, and each one presents a unique challenge. One such code is P028E, which refers to a charge air cooler cooling fan control circuit high. In simpler terms, this code indicates that there is a problem with the charge air cooler (CAC) system, specifically the cooling fan control circuit, and it is operating at a higher voltage than it should be. In this article, I will explain what this code means, how to diagnose the issue, and provide solutions for repair.

Understanding the Charge Air Cooler System

Before delving into diagnosing and fixing the problem, it’s essential to have a basic understanding of the charge air cooler system. The charge air cooler is an essential part of most modern diesel engines that use turbochargers or superchargers to increase power output. It cools the compressed air coming from the turbocharger or supercharger before entering the engine. This cooling process increases air density, which leads to more oxygen being available for combustion, resulting in more power being produced.

The air travels through a series of tubes and fins that are cooled by an air or liquid-based system, depending on the engine’s design. The CAC system typically includes a cooling fan that draws air through the fins to help dissipate the heat. The fan is controlled by an electronic module that receives input from various engine sensors, such as the coolant temperature sensor, intake air temperature sensor, and ambient air temperature sensor, to determine when the fan should turn on and at what speed.

Understanding OBD-II Code P028E

When the charge air cooler cooling fan control circuit high code appears, it means that the electronic module that controls the fan has detected that there is too much voltage being sent to the circuit that powers the fan. This voltage is above the expected range and is often caused by a malfunctioning electronic module, wiring issues, or a defective fan motor. The system may also set the engine into limp mode, causing it to run at reduced power output to prevent further damage.

Diagnosing the Issue

To diagnose the issue, you will need an OBD-II scanner to read the code and any other codes that might be present. Once you have the code, you can begin your diagnosis by inspecting the wiring and connectors for the fan and the electronic module. Look for any signs of damage or corrosion, and ensure all connections are secure.

Next, you will need to check the fan motor for proper operation. You can do this by using a multimeter to check the voltage and resistance of the motor. If the voltage and resistance are within the expected range, the fan motor is likely functioning correctly. However, if the motor fails these tests, it will need to be replaced.

If the wiring, connectors, and fan motor all check out, the issue may lie with the electronic module that controls the fan. This module may need to be replaced or reflashed with the latest software to resolve the issue fully.

Solutions for Repair

The solution to the problem will depend on the diagnostic results. If the wiring or connectors are damaged or corroded, you will need to repair or replace them. If the fan motor is faulty, you should replace it. If the electronic module is the issue, you can replace it, but it is essential to ensure it is programmed correctly to avoid further issues.

It’s worth noting that if the CAC system is not working correctly, it can cause other problems with the engine, such as poor performance or reduced fuel efficiency. Therefore, it’s important to resolve any issues with the CAC system quickly.

Frequently Asked Questions

1. Is the charge air cooler system the same as the intercooler system?

No, they are not the same, though they perform similar functions. The intercooler system is responsible for cooling the compressed air coming from the turbocharger or supercharger before entering the engine, while the charge air cooler cools the already compressed air before entering the intercooler.

2. How can I prevent issues with the charge air cooler system?

Regular maintenance of the charge air cooler system can help prevent issues, such as cleaning and inspecting the fins and checking the connections and wiring for any signs of damage.

3. Can I drive my vehicle with the P028E code, or is it dangerous?

It is not recommended to drive your vehicle with the P028E code present as it could affect the vehicle’s performance and lead to further damage if left untreated.

4. Can I fix the issue myself, or do I need to take it to a mechanic?

The issue can be fixed by yourself if you have the technical knowledge and tools necessary to diagnose and repair it. However, if you are unsure, it’s best to take it to a qualified mechanic who can diagnose and fix the issue correctly.

5. Is there a chance that the issue is caused by multiple problems, and how can I know?

Yes, it’s possible to have multiple issues contributing to the P028E code, and it can be challenging to diagnose. That’s why it’s essential to follow a systematic approach to diagnosis and ensure all wiring, connectors, fan motor, and electronic module are inspected and tested before making any repairs.


In conclusion, the charge air cooler cooling fan control circuit high code, or P028E, can be an indication of a problem with the charge air cooler system. It’s essential to understand the basics of the system, diagnosing the issue, and providing the right solutions to fix it. If you have any doubts regarding the process, it’s best to take the vehicle to a qualified mechanic for inspection. Regular maintenance of the charge air cooler system can also help prevent any issues from arising. With the right approach, the charge air cooler system can perform optimally, leading to better performance and improved engine efficiency.

Scroll to Top