The Variable Valve Timing (VVT) and Variable Valve Lift (VVL) systems contribute to better fuel mileage and other things. The P0028 code sets when the vehicle’s main computer (powertrain control module or PCM) detects problems with these systems or any of their related components. And while many modern platforms use VVT, this exact code only appears on a few.
With variable valve timing (which is very common on today’s engines) camshaft timing can be altered dynamically while the engine is under load. This strategy is used to enhance fuel economy, increase power, and reduce emissions.
What Does the P0028 Code Mean?
Diagnostic trouble code (DTC) P0028 stands for “Intake Valve Control Solenoid Circuit Range/Performance (Bank 2).” Note that the definition of this code and the setting conditions may differ depending on the vehicle’s manufacturer. For more information, please see the appropriate repair manual or database.
The P0028 code may be set in a couple of ways, depending on the vehicle. In some vehicles, P0028 sets if the PCM determines that the VVL oil pressure switch has been in the “on” or “off” position for longer than the expected time.
In other vehicles, this code sets if the PCM detects that there is a difference between the actual camshaft position and the desired camshaft position. This problem is potentially due to an issue with the VVT solenoid operation. P0028 is related to the OBD-II codes P0026, P0027, and P0029, particularly the electrical circuits that control the solenoid directing oil pressure to the cam phaser on Bank 2.
The VVT works by using an actuator(s) mounted on the end of the camshaft(s). The PCM controls the VVT solenoid(s) so it can apply the appropriate oil pressure to the actuator(s). Each actuator then changes the position of its corresponding camshaft and thus alters the valve timing.
Meanwhile, the VVL allows the PCM to modify the distance that the valves are lifted from their original positions. Like the VVT, the VVL is also used to enhance the performance of the engine.
The VVL system makes use of a camshaft with different profiles for low and high-speed operations. A typical VVL set-up has three rocker arms that operate two intake valves. The PCM commands an oil control solenoid to apply oil pressure to drive a pin that would lock the rockers together. Because of this, the valves are controlled in such a way that they follow the cam profile designed for high-speed operation.
The VVL system has a diagnosis switch located near the control solenoid. This switch lets the PCM know if oil pressure was applied to the VVL system.
You can learn more about VVT and how it can trigger codes like P0028 in our discussion about variable valve timing and camshaft angle.
What are the Possible Causes of the P0028 Code?
Most OBD-II codes have multiple possible causes, and the same goes for P0028. Below is a list of just some reasons the P0028 code sets in your vehicle’s memory:
- VVL diagnostic switch failure
- VVL solenoid failure
- VVT solenoid failure
- VVT actuator failure
- Wiring issue
What are the Common Symptoms of the P0028 Code?
There are a handful of signs that may indicate that you’re dealing with DTC P0028. If you notice a combination of the symptoms listed below, your best option is to check your vehicle immediately or have a professional check it at your nearest auto shop.
- Check engine light illumination
- Rough idling
- Reduction in engine power at some engine speeds
- Engine misfiring may be present at some engine speeds
- Increased fuel consumption
How to Diagnose the P0028 Code
You need proper and accurate diagnosis to reach an effective and long-term solution for OBD-II codes such as P0028. However, this may pose a challenge as there are several possible causes behind the P0028 code.
There are a lot of reliable sources that contain troubleshooting information for OBD-II codes such as the P0028. Repair manuals and databases are the best sources because they have detailed and specific information procedures. They also contain clear and easy-to-understand diagrams and pictures to help visual learners as well.
Meanwhile, there are other sources available that contain additional information on these trouble codes both in print and online. Below is a video resource that can help you find out more about the P0028 code:
How to Fix the P0028 Code
As mentioned above, a long-term P0028 fix will not be possible if you don’t get to the bottom of the issue and determine the exact root cause. In addition, different vehicles get built and oriented differently. Troubleshooting procedures will differ according to the vehicle manufacturer. Simply put, there is no one-size-fits-all solution to P0028 or other trouble codes.
The good news is that repair manuals and databases provide accurate repair information to help the seasoned DIYer. However, if you’re only starting out with DIY repairs and are not confident enough in your skills, you can always have a certified mechanic or technician do the repairs for you. This will help you avoid making expensive and harmful mistakes while repairing your vehicle.
Other Notes About P0028
It’s common to see the engine code P0028 on Subarus. If you own a Subaru and encounter any or a combination of the symptoms described above, you can look for the appropriate technical service bulletin (TSB) that will give you diagnosis and instructions for an appropriate P0028 Subaru fix.
It must be noted that specific repair procedures will vary depending on the manufacturer, so it’s best to consult the right repair manual. You may also see a professional mechanic for repairs and other tips, especially if you don’t know how to address the issue yourself.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.