P0455 and P1448 Codes, please help.

Hello,
I have a 2003 Max with P0455 (Evap Leak - Large) and P1448 (Manufacturer Control Aux Emission Control) codes.
I've already changed the gas cap and the codes came back. Does anyone have any idea what it might be?

Thanks in advance.

Hello,
I have a 2003 Max with P0455 (Evap Leak - Large) and P1448 (Manufacturer Control Aux Emission Control) codes.
I've already changed the gas cap and the codes came back. Does anyone have any idea what it might be?

Thanks in advance.

The FSM has following clues, check out page EC-390

DTC P0455 EVAP CONTROL SYSTEM (GROSS LEAK)
Possible Cause


Fuel filler cap remains open or fails to close.

Incorrect fuel tank vacuum relief valve

Incorrect fuel filler cap used

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

Fuel tank temperature sensor

O-ring of EVAP canister vent control valve is missing or damaged.

EVAP control system pressure sensor

Refueling control valve

ORVR system leaks

Thanks! That gives me a few places to start.

Thanks! That gives me a few places to start.

There seems to be 4 valves and 2 sensors used in ctrl of this function. That means also (not mentioned in the FieldServiceManual) lots of bad connector pin and gnd point possibilities...

I think I found the problem. Thanks to Nahkpohjola for listing all the components for me and to Wallykarp who had a similar problem with a '98 Max.

I looked and all the connections and they all seemed dry and corrosion-free. I then took a closer look at the valve on the charcoal canister, I put 12 volts to it and sure enough it was stuck open.

Problem was that the bolts that held it onto the canister broke so I ended up having to buy a canister too. Ouch! (It's my wife's car, but it it were my own, I would have just gotten some big cable ties and strapped it on to the canister. Since there's an o-ring that seals it, not a gasket, I think it would not have leaked. But for her I wanted it done right the first time and not have to mess with it in the future.)

I'll post again if there's any new, but so far so good.