I have a Nissan and these days the Check Engine Light just came on. It was just Tuesday, you know. So, if you are in the same situation then normally you would have two choices: get your car to a dealer or save few hundred bucks by fixing yourself. I chose the later option, it sounded more fun.
DTC code P0455 - Check Engine Light
So the first step into troubleshooting a Check Engine Light is to use a On-Board Diagnostics (aka OBD) scanner tool (I use an ELM327) in order to find out what is the Diagnostic Trouble Code (aka DTC) that caused the malfunction indicator light.
Depending on the scanner tool you have (I use a software that communicates with the ELM327 scanner via USB) you would get an info about the MIL Status (On|Off) and the number of DTCs stored in car's Engine Conrol Unit (aka ECU).
By reading that list of stored DTCs you might encounter, like myself, a P0455 DTC code alone or together with some other P045* codes. Some scanner tools tell you what the code mean, some don't. However, you can use the www.obd-codes.com webpage to check for your particular code. It will tell you what it means, the symptoms, the cause and the possible solutions. However, I have my car's model specific Service Manual which tells me everything I need to know about it.
What is P0455
P0455 EVAP CONTROL SYSTEM - This diagnosis detects a very large leakage (fuel filler cap fell off etc.)
A very large leakage could mean anything from a loose fuel filler cap to a leak or a damaged piece in EVAP system:
- Fuel filler cap remains open or does not close
- Incorrect fuel tank vacuum relief valve
- Incorrect fuel filler cap used
- Foreign matter caught in fuel filler cap
- Leakage is in line between intake manifold and EVAP canister purge volume control solenoid valve
- Foreign matter caught in EVAP canister vent control valve
- EVAP canister or fuel tank leakage
- EVAP purge line (pipe and rubber tube) leakage
- EVAP purge line rubber tube bent.
- Loose or disconnected rubber tube
- EVAP canister vent control valve and the circuit
- EVAP canister purge volume control solenoid valve and the circuit
- Fuel tank temperature sensor
- O-ring of EVAP canister vent control valve is missing or damaged.
- EVAP control system pressure sensor
- Refueling EVAP vapor cut valve
- ORVR system leakage
The EVAP system is quite simple, for instance the fuel tank and the fuel filler cap are part of it. Below is a schematic for the EVAP system of my car:
How to fix it
Very large leak could mean, among others, a loosen fuel filler cap. So I checked the fuel filler cap first (loose & tide + drive few miles) but the DTC code was still there.
It might also mean a loose or disconnected rubber tube so I checked also the rubber tubes connected to the EVAP system in the engine compartment. Everything seemed OK.
Then I checked the EVAP purge volume control solenoid valve (which normally should be closed). Try to blow through the A & B, no air should pass. By applying a 12V to its terminal connector the air should pass between A & B, which means it works!
Next thing I checked was the EVAP canister vent control valve, which normally should be opened. By blowing air between A <-> B it should pass. By applying a 12V (for 1sec) to the terminal connector the valve solenoid magnetizes and closes so no air should be able to pass between A and B.
However, in my case it was even worse. The solenoid inside the valve seemed to be blown, like it exploded inside the valve which caused the valve shell to crack as you can see below.
So it was the time to change it. I ordered a new one on eBay for $26 (instead for +110 EURO at dealer), it took less than 5 minute (no need to lift the car on jack stands) to dismount the old one and mount the new one. Just locate the EVAP canister on your car (it should be close to the muffler) then locate the EVAP vent control valve. First remove the 12V connector then dismount the valve by rotating it counter-clockwise. Mount the new one in reverse order. That's it!
How to test your fix
When working on a vehicle after an MIL status it's recommended to not clear the DTC code, if possible, so that the MIL remains on after the repair. If it was the correct repair, the MIL will turn OFF on its own while driving the vehicle through its drive cycle and signals to the driver that the repair fixed the problem.
If the MIL does not turn off, then additional repairs may be required (probably there are some additional DTC to be fixed).
As you can see it takes only few minutes while you are going to save at least $200 (depending on your country & dealer).
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