The P0446 fault code is a common OBD-II diagnostic code, standing for EVAP System Vent Control Circuit Malfunction.In the previous article, we introduced the signs of EVAP system failure. Today, we will mainly explain the fault code P0446 and see which part of the EVAP system failure it is related to.
The EVAP system (evaporative emissions control system) prevents fuel vapor from being released directly into the atmosphere. Instead, it stores it in an activated charcoal canister and then, at the appropriate time, directs it through a purge valve into the intake manifold for combustion.
When the engine control module (ECM/ECU) detects abnormal voltage in the EVAP vent valve circuit, unexpected switch operation, or a clogged line, the P0446 fault code is triggered, and the engine check light illuminates.The P0446 code can often be diagnosed with an Autel scanner.
The P0446 fault code was detected using Autel AL619.
Although the P0446 fault code doesn't severely affect engine operation like ignition or fuel injection system failures, it can still cause some noticeable symptoms:
When the check engine light comes on, you need to use an Autel scanner to detect the P0446 code.
Many owners find that their vehicles still drive normally. However, if the P0446 fault code is not addressed for a long time, it may lead to fuel vapor leaks, excessive emissions, and even failure of the annual inspection.
A bad vent valve can cause the P0446 code to appear.
To diagnose P0446, we recommend using an Autel scanner or other auto diagnostic tools. The process is as follows:
Confirm whether P0446 is the only fault or is accompanied by other EVAP-related codes (such as P0440, P0441, or P0449).
Understand the operating conditions when the fault occurred.
Use the Autel scanner to control the EVAP vent valve to confirm normal operation.
Use a multimeter to test voltage and resistance to check for opens or shorts.
To see if there is any blockage, rupture or carbon particle leakage.
A common method involves injecting smoke into the EVAP system to locate leaks.
Confirm that the data is within the normal range.
Diagnose EVAP system status with Autel scanner.
Depending on the cause, solutions include:
After repairs are complete, use an OBD-II diagnostic tool to clear the fault code and conduct a road test to confirm that P0446 does not trigger again.
The owner reported that the check engine light was on. An Autel scanner read the code: P0446. During the active test, the vent valve did not respond. The owner ultimately determined that the vent valve coil was burned out. Replacement resolved the issue.
If you are having trouble identifying the components of the EVAP system during maintenance, you can refer to the following explanation video using the Toyota Camry as an example:
There was a noticeable gasoline odor from the rear of the vehicle, and the exhaust gas emissions failed the annual inspection. Using an Autel scanner to read the fault codes revealed P0446 and P0442. Further inspection revealed a ruptured activated charcoal canister and carbon particles blocking the pipes.
The canister and pipes were replaced, and after clearing the fault codes, the problem was completely resolved.
The owner complained about increased fuel consumption. The fault code read: P0446. Inspection revealed a bend in the pipe, preventing vapor from venting. Reinstalling the pipe restored the problem.
From a safety perspective, the vehicle can usually be driven after the P0446 fault occurs and will not break down in the short term. However:
Therefore, it is recommended to use an Autel scanner to locate the problem and repair it promptly.
The P0446 code may cause a failure in the annual emissions test.
The P0446 fault code indicates an abnormality in the EVAP system ventilation control circuit and is common in Toyota, Honda, Chevrolet, Nissan, and other models. While it won't immediately cause a breakdown, it will trigger the fault light and affect emissions and fuel consumption.
Using the Autel scanner, technicians and vehicle owners can quickly read the code, perform proactive testing, and accurately locate the problem component, enabling efficient repairs.
Resolving P0446 promptly will not only restore your vehicle to normal performance, but will also prevent annual inspection failures and extend the life of the EVAP system.
No tool is perfect, and it's inevitable that you'll encounter various issues during use. Today, we'll focus on common software glitches with the Autel key programmer and share solutions to help you use it more smoothly and efficiently.
Today, we will provide a comprehensive introduction to the upgrade methods for Autel scanners, covering the steps during the free update period, how to purchase and use the software upgrade service after the subscription expires, and our advantages over other Autel dealers, to help you fully resolve any questions you may encounter during the upgrade process.
In our previous post, we shared how to program a BMW key using an Autel key programmer. Today, we'll take a different approach and show you how to program a Honda key fob at home, and explore the specific methods that make this easy.
