Getting a code P0456 (v.small evap) now. This is the 8th time the CEL has come on with this code in the last 3 months.

They checked the system with smoke and vacuum (twice, now) and can't find any evidence of a leak, so they clear the code and tell me I'm good to go.

Each time, the light stays off... until the next time I am doing about 70-75 and set the Cruise on: then the light always comes on after 5 or 10 minutes of steady 75 mph cruising. Getting tired of taking the car back into the shop.

The light never comes on with that code unless I am in the above situation!
Strange...


Suggestions appreciated. Especially interested to hear if anyone's had this code/problem before on their 2k2+ and what the resolution was.

 

Paralyse,

It's obvious who ever you took your car too didn't know how to properly diagnose your
Max. I've had the same code and was able to solve my problem. Here's some thing
could be wrong with your car.

P0456 DTC P0456 EVAP CONTROL SYSTEM: This diagnosis detects very small leaks in
the EVAP line between fuel tank and EVAP canister purge volume control solenoid
valve, using the intake manifold same as a conventional EVAP small leak diagnosis.
If ECM judges a leak which corresponds to a very small leak, the very small leak P0456
will be detected. If ECM judges a leak equivalent to a small leak, EVAP small leak P0442
will be detected. If ECM judges there are no leaks, the diagnosis will be OK.

Possible Causes: Foreign matter caught in fuel filler cap
Leak 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 leaks
EVAP purge line (Pipe and rubber tube) leaks
EVAP purge line rubber tube bent
Blocked or bent rubber tube to EVAP
control system pressure sensor Loose or disconnected rubber tube
EVAP canister vent control valve and the circuit
EVAP canister purge volume control solenoid valve and the circuit
Absolute pressure sensor
Fuel tank temperature sensor
O-ring of EVAP canister vent control valve is missing or damaged.
Water separator
EVAP canister saturated with water
EVAP control system pressure sensor
Refueling control valve
ORVR system leaks
Fuel level sensor and the circuit
Foreign matter caught in EVAP canister purge volume control solenoid valve
Incorrect fuel tank vacuum relief valve
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close.

In my case it was the EVAP canister. I took it apart and used compressed air
to clean out all the hoses of carbon crap and now it runs fine without any problems.

If you are taking this car to a Nissan Dealer make sure you INSIST they follow the
diagnostics procedures outline in the Factory Service Manual section Engine Control
System Section EC page 417-431 (DTC P0456 EVAP Control System) Good Luck!!

Mike

 

Thanks for the info Mike!