Experiencing the frustration of a persistent P0456 code? This OBD-II trouble code indicates a small evaporative emission (EVAP) system leak, a common issue that can be tricky to diagnose. Like many, I chased this code for a while, replacing parts based on common fixes, only to see it reappear. If you’re facing the same problem, this guide shares my experience and the solution that finally worked for me: replacing the leak detection pump.
Initially, I addressed the basics. Thinking it might be a simple fix, I replaced the original gas cap with a new OEM unit. Given the age of the car, this seemed like a logical first step. I also noticed a fuel smell and suspected a leak from the fuel level sending unit. Upon inspection, it was indeed cracked and leaking, so I replaced it. At the same time, my fuel pump was showing signs of failure, triggering other codes (unfortunately, I don’t recall the specific codes now) and causing acceleration problems. Although not covered by the recall, I replaced the fuel pump as well.
Despite these replacements and a professional fuel system smoke test that showed no leaks, the P0456 code stubbornly returned. This led me to suspect the leak detection pump itself. After doing some research and considering the process of elimination, I decided to replace this component. The result? The P0456 code vanished and hasn’t come back!
For DIY mechanics, replacing the leak detection pump is a manageable task. Here’s a step-by-step guide based on my experience:
Step-by-Step Leak Detection Pump Replacement
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Raise the Vehicle: Safely elevate your car. I used ramps for the front and jack stands for the rear to provide ample working space underneath.
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Support the Exhaust: Use a mini-jack or similar support to hold the weight of the catalytic converter and downpipe assembly. This is crucial before detaching the exhaust system.
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Disconnect the Exhaust: Remove the exhaust system section located south of the downpipe. This will provide better access to the work area.
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Access the Pump:
- Remove the rear-left wheel to gain access to the wheel well.
- Carefully pull back the wheel well liner. This is typically held in place by plastic fasteners and rivets. You may need to drill out a couple of plastic rivets to fully remove it.
- Remove the muffler heat shield. This is secured by an aluminum rivet (behind the wheel well liner – you’ll need to drill this out) and a couple of plastic fasteners.
- With the heat shield removed, the leak detection pump will be exposed and accessible.
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Identify and Replace the Pump: I ordered part number 31392490, assuming it was the correct complete assembly. However, this part number includes pre-attached hoses that are routed above the rear subframe – a much more involved replacement. In hindsight, I recommend ordering just the pump itself (part number 30774518).
Instead of replacing the entire assembly with hoses, I opted to reuse the existing hoses. Using a heat gun to gently warm and loosen the connections, I carefully detached the hoses from the new pump unit and attached the original hoses. Given that my car has spent its life in California, where temperature variations are less extreme, and the hoses are not directly exposed to engine heat cycling, they were still in good condition.
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Reassembly: Reassemble all components in reverse order. Ensure all fasteners are securely in place and the exhaust system is properly reconnected.
Important Considerations and Future Maintenance
While replacing just the pump worked for me in this instance, if you are planning a rear suspension refresh in the near future, especially if you live in an area with strict emissions regulations, consider inspecting or replacing the EVAP system hoses at that time. With the rear subframe dropped, access is significantly easier, and the hoses themselves are relatively inexpensive. It’s proactive maintenance that can prevent future issues and ensure your EVAP system remains in top condition.
By focusing on the leak detection pump, I successfully resolved the persistent P0456 code. Hopefully, this DIY guide will help you troubleshoot and fix this frustrating EVAP system issue on your vehicle.
