Technical OBD errors

[Speary8]

Fiat ducato maxi multi jet 130 motorhome
I have just run a diag test and the following errors appeared P0402 exhaust gas recirculating flow excessive detected P0638 throttle actuator control range / performance bank 1 Can somebody please advise what these actually mean. Eg what do I need to fix Thanks

 

[RS3100]

I saved this from another forum a few years ago. The person who replied ran a large fleet of Ducato vans and serviced all their own vehicles, so was quite knowledgeable.

I've owned a 2009 (09 plate) 2.3 Ducato Motorhome for 3 years, its
done 30,000 miles in total, and has been regularly serviced.
I recently drove it to Southern France for a holiday, and one day when I
started the engine, it would only tick over and wouldn't rev
up at all.
The accelerator pedal felt normal, and was operating up and down
freely as usual, but the engine just wasn't responding?
After about an hour of head scratching, and trying repeated starts there
was no change, so I called for breakdown assistance.
The fault couldn't be cured on-site, so we were recovered to a
French Fiat garage about 20 miles away.
The garage prioritised diagnosing our fault, and the next day they fitted
two main (genuine Fiat) parts as follows;
0071724306 Throttle body/Electrovanne EGR (E.S.) and 0504388760
Cables Assemblies
Their invoice shows two fault codes detected; P0638 and P0402
The van appeared to be performing normally again, so I paid their bill
and we headed North towards Calais.
The next morning on start up, the same fault happened again, the van
started OK, but had little or no throttle response.
Fortunately, this time the fault rectified itself after around 1 minute, and
the engine could then be revved up normally.
As we were by then around 200 miles North of the garage who'd
repaired the fault, we decided to continue on to Calais.
We are now back in the UK, and the van has done the same thing on
two further occasions, luckily clearing itself both times.
The fault is intermittent (for the moment) but obviously I would like to
get it permanently rectified.
Any thoughts on possible causes, and/or suggestions of the best way
forward from here?
Cheers, John

Hello,
I would say that the garage that diagnosed the fault were correct and the
throttle body did need to be replaced. However; in most instances when
the throttle body has been malfunctioning this puts a great deal of stress
on the electrical solenoid valve that operates the EGR as it frantically
tries to balance the inlet manifold pressure due to an unresponsive
throttle body. This solenoid valve sits behind the small metal plate that
is below the windscreen scuttle. Replacing this should solve the
problem. You can test the theory by locating the rubber pipe that comes
from the right hand side of the solenoid as you look at the engine and
gently pull it backwards and off. On occasions when we have had this
problem, we have switched off the engine, removed this pipe and
started the engine with no fault present.
It is known as an EGR solenoid valve. Fiat part number is 46524556
and equivalents are made by Pierburg and Intermotor for less than the
price of the Fiat item. Most motor factors should be able to supply these
if you give them the Fiat part number.

 

[Anthony489]

Hi Speary8

You don't say what year your van is, which would help. The comments below apply to 2006 to 2010 era vans, later ones may differ.

The error codes point to a problem with the Exhaust Gas Recirculation (EGR) system. There are several components involved in this, the EGR valve (RHS of engine, low down) from exhaust to inlet manifold, the EGR solenoid valve (under the scuttle) which controls the EGR valve via vacuum hoses, and finally the Throttle Body (in front of the engine) which controls air flow into the inlet manifold. All these components perform a balancing act to get the amount of EGR right under different engine operating conditions, so a fault in one may result in a spurious fault indcation for another.


It would be great if error codes told you exactly what to replace, but they aren't precise enough to do that. The codes plus experience plus other diagnostics are what is required. My suspicion would be the throttle body. To change this needs about £150 to £200 in parts plus several hours labour because of the dismantling to get at it. However, in view of the cost, and the risk that it will turn out to be something else that's wrong, I'd suggest you get an experienced person to take a look at your setup before leaping in to change components.

Incidentally, the solenoid valve is designed to continually adjust its setting during normal driving so I am sceptical of the "wear out due to extra work" theory. Having said that it's a £40 component and easy enough to change so might be worth a punt.

 

[RS3100]

Hi Speary8
Incidentally, the solenoid valve is designed to continually adjust its setting during normal driving so I am sceptical of the "wear out due to extra work" theory. Having said that it's a £40 component and easy enough to change so might be worth a punt.

And easy to test by removing the rubber pipe without spending anything initially, assuming the throttle body has either been replaced or is known to be OK.

 

[Crossingkeeper]

This thread to which RS3100 contributed may also be relevant.

Note the last post re. time taken to change throttle body!

https://www.fiatforum.com/ducato/483922-ducato-x250-fault-codes-p0403-p0638.html