I have engine codes p0401 and p0455 on a 1998 F150 4x4 5.4l. I have found detailed procedures on how to resolve these codes. I have checked the egr ports and it was clean. However, I found the vaccuum lines located behind the battery housing completely corroded. There is rubber housing where the EGR vaccuum assembly connects too, and it connects to another vaccuum assembly.

My question is - what is this other assembly called and where does it go ? I followed the vaccuum lines back to a black box above the front passenger tire above the plastic tire well? I tried to explain this to the parts guy at the ford dealership but no success. I have tried to find it in my Haynes and Chilton truck manual and still nothing.... Any insight would be appreciated! thanks

 

Are you talking about the container-ish thing that you have to pull off the battery holder?

It was my understanding that it has something to do with the A/C...

 

No - If you were to follow the vaccuum lines from the EGR valve and the vaccuum on the TB, they connect to a different set of vaccuums. I would like to know what they are called and where they go. I will try to take some pics tonight and post them tomorrow. It is hard to explain.

 

A P0455 code is usually caused by a leak in the evaporative system, most likey a loose gas cap or a vent line that has come loose.

A P0401 code is an EGR insufficient flow problem, either caused by the EGR valve not opening enough (carbon build-up), or a leak in a vacuum line somewhere that controls the movement of the EGR valve, or a defective DPFE sensor, which measures the EGR flow through an orifice using the differential pressure before and after the orifice.

But.....I fail to see how the two codes could be related?????

Hmmmmmmmm.........

 

sernabe,

Is it number 6,7 or 8?

Regards

Jean Marc Chartier

 

it is in the same vacinity as number 2. But that is the black box i was referring too. thanks

 

sernabe,

Does this picture help? The view is from the passenger side and the thick black arrow is pointing towards the radiator.

JMC

 

Had the exact problem in my wifes 97 5.4 Expy.. P0401
Found the vac line behind the battery was rotten at the rubber 4way connector..
I went to autoparts store and bought some connectors and line then bypassed the connector and rotton line.

This line was the vacuum supply to the egr relay, causing a insufficient egr flow..

 

thanks everyone -

JMC do you know where number goes on your diagram?

 

sorry about that... I meant to say, " do you know where number 6 goes on your diagram?"

 

sernabe,

Yes, number 6 goes to the vacuum resevoir over by the battery.

JMC

 

Yes, that's what I was talking about.

On my'97 that container is behind the battery (between the battery and the fender).

I looked around today, and the lines split by the battery and 2 of them end up going down to the transfer case. Some of the others go into the fender where I cant track them.

 

The reason for the vacuum tanks is to provide vacuum when the engine is in a sutuation where little or no vacuum is available. The HVAC system uses vacuum to change the blend door position. It defaults to defrost in the event of a loss of vacuum. There has to be vacuum available to keep it from defaulting, hence the resevoir. The front axle uses vacuum to switch between modes so it also needs a consistant supply.

JMC

 

Thanks everyone!!! Here are the part numbers incase anyone wants to know....

EGR VACCUUM ASSEMBLY = F75Z-9E498-CE

FORD CALLS THE SECOND ONE "CONN ASSY EMI" (the one that dissappears into the passenger fender) = F75Z-9E498-GA

For all the vaccuum hoses and connectors total $105.00

This should resolve p0401 (FINGERS CROSSED) - now its time to fix p0455.
Anyone have a good place to start?

 

"EGR VACCUUM ASSEMBLY = F75Z-9E498-CE"

Is that one just basically all the hoses?

Also, the one that disappears into the fender, what does that connect to? The defrost stuff?