Acura MDX Emission System Problem: Troubleshooting and Fixing the Check Engine Light

by parker
YouTube video

acura mdx


In this article, we will be discussing a common issue with the Acura MDX, specifically related to the emission system. Many owners have reported that the check engine light is on and displaying a message that says “Emission System Problem.” We will dive into the details of this issue, its possible causes, and steps to troubleshoot and fix the problem.

Step 1: Diagnostic Scanning

The first step in troubleshooting the emission system problem in the Acura MDX is to perform a diagnostic scan using a compatible scanner. For this demonstration, we will be using the Autel MaxiSys MS906BT. Connect the scanner to the vehicle’s OBD2 port and power it on.

Step 2: Reading the Codes

After the scanner is connected and powered on, go into the generic OBD2 mode to read the trouble codes. In this particular case, three codes were detected: P0420 (Catalyst system efficiency below threshold bank 1), P0497 (Evap system low purge flow), and P145C (Evap system purge flow malfunction).

Step 3: Identifying the Purge Valve

To address the issue of low purge flow, the first component to inspect is the purge valve. The purge valve is responsible for controlling the flow of vapors from the gas tank to the engine intake system for combustion. Locate the purge valve, which is usually situated close to the engine and connected to the intake manifold.

Step 4: Inspecting the Purge Valve

After locating the purge valve, remove any covers or components obstructing access to the valve. In this case, a cover had to be removed to gain access to the purge valve. Inspect the valve for any signs of damage or wear. In some cases, a cracked or faulty purge valve can cause insufficient flow or improper sealing.

Step 5: Testing the Purge Valve

Using the scan tool, activate the purge valve to see if it opens and closes properly. This can be done by selecting the appropriate option in the software. Pay attention to any clicking sounds that indicate the valve is functioning. In this case, a slight click was heard, but it was weak, suggesting a potential issue with the valve.

Step 6: Confirming Insufficient Flow

To confirm the insufficient flow issue, disconnect the hose connected to the purge valve and blow compressed air through it. If the flow is restricted or there is significant resistance, it indicates a problem with the valve. In this case, the valve was not allowing enough flow through, leading to the detection of the trouble code.

Step 7: Replacing the Purge Valve

With the diagnosis of a faulty purge valve, the next step is to replace it. Order a new purge valve and install it in place of the old one. Ensure proper sealing and secure all connections. After the installation, retest the purge valve to confirm that the flow has been restored and the code is no longer present.


In this article, we discussed a common issue with the Acura MDX, namely the emission system problem indicated by the check engine light. We provided step-by-step instructions on how to diagnose and troubleshoot the problem, focusing on the purge valve as a potential cause of low purge flow. By following these steps, you can address the issue and restore proper functioning to your Acura MDX’s emission system.

Remember, if you continue to experience issues or if additional trouble codes are present, it is recommended to consult with a professional mechanic or visit an authorized Acura service center for further assistance.

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