Hello all.
Problems again with my FIAT Ducato X250 2.3 litre 2007 (built 2006) Ducato motorhome.
Had problems just over a year ago with a split turbo hose and P0638. Garage replaced both the hose and throttle body (sticker on it says (refurbished).
All ok but did have P0638 coming up occassionally which cleared after a few re-starts.
Did notice the odd stutter, almost like taking your foot off the accelerator and back on again but always cleared and ran fine. BTW, did the same with cruise control on.

However, last week both P0638 and P0403 came up and the van when into limp'ish mode with no power above 2500-3000RPM, so decided it was time to do some checks.
For P0403 (EGR exhaust gas recirculation) found the EGR solenoid did not appear to be working, waiting for a replacement now so no further with this.

For P0638 (throttle actuator control range) started by removing the throttle body for bench testing. Checking onto the plug found high resistance between every combination of pins so decided the body could be faulty. Got another one (slightly different design but should be ok on the van) and re fitted it putting in new gaskets as needed, which the garage had not done. Took the old body apart and when the electricery bit was broken open there was a definate burnt smell from it and a very black burnt looking PCB.

Reset all OBD codes but they came back when the engine was started.
Checked volts on the plug from the engine ECU but got 'strange' readings. Definate earth, but only 3 and 3.5 Volts on the plug, would have thought one should be either 5 or 12 Volts to activate the throttle ?.
After a quick check with a local vehicle electrician (3 weeks before he could look at van) he suggested there could probably be a broken/corroded wire which I have heard of before.
So just now (between rain showers) I have taken all the covering off the loom that runs from the ECU to the engine. No noticable corrosion, but will buzz through every wire to be certain.
Slightly suspicious the ECU might be the problem, but due to replacement and re-programming costs want to be certain wiring is good before I look further into it.

So, am I missing something obvious, or should I continue checking wiring and sensors ?.

Thanks, Martin.

I saved this from another forum some time ago. Similar problem. The author ran a fleet of Ducatos and maintained them as well as servicing and reapiring customers vans.

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.

Thanks for that RS3100. This could explain why bothe the solenoid and throttle body have both failed. As I said earlier, the throttle body electronics board(s ?) have burnt out, also the solendoid does not work and gets very hot under test.

Have been through the wiring harness and no faults found, but while putting everything back together thought I would check the fuses.
F11 E1 secondary fuse had blown so replaced.
Can find little information on what this fuse supplies but suspect it will be power for the throttle body and maybe the solenoid.

Too dark for further checks so will do a bit more research.

Thanks again.
Martin, GM6VXB

Hi GM6VXB

Fuse F11 (15 Amp) supplies +12V to the EI (Electronic Injection) Secondary Services. These are:
Throttle Body
EGR Solenoid Valve
Glow Plug Controller (Logic Circuits)
Lambda Sensor
Oil Vapour Heater (A 20 watt resistor mounted in the breather pipe on Northern Europe spec. vehicles.

The last item doesn't do much except in very cold weather, so its 2 pin connector can be disconnected when faultfinding. It sits in a hose near the bulkhead on the right side of the engine as you look at it.

Clearly, nothing much will work properly until F11 is intact and the cause of overcurrent removed.


I am a bit sceptical of the idea of the EGR solenoid valve "wearing out" due to increased workload. It uses a pulse width modulated signal at a few hundred Hz to move its internals against spring pressure. This varies the vacuum supply on its output hose, which in turn operates a vacuum diaphragm on the EGR proper. It's therefore designed to cope with a varying control signal and will be adapting its position all the time you're driving. It does run warm-ish. A vacuum gauge teed in will tell you if it's working, but a new one is only about £70 and may be the expedient fix.

The early Wahler throttle bodies use a stepper motor with a 90 degree swing, which moves the throttle disc against a return spring. The connections are Pin 3 to Ground, Pin 2 to +12V and Pin 1 to a varying PWM signal from the ECU. The later Marelli type uses a geared servomotor with an internal feedback pot to establish the position, and are reckoned to be a more robust and reliable design less prone to sticking. The Marelli can be retrofitted but has a different connector and therefore needs a short length adaptor cable. Note that on the 2.3 engines both types operate "open loop" as far as the ECU is concerened, i.e. there is no feedback signal to tell the ECU its position, it just assumes that it's doing as it's told.

I have no idea what information the ECU uses to decide if there is a fault with the throttle and/or EGR valve. Possibly it takes information from the manifold absolute pressure sensor which is downstream of the throttle, in the manifold. Both the throttle body and the EGR valve are used to control EGR under different operating conditions, and perform a balancing act where the throttle partially closes as the EGR opens and vice-versa.

Cheers, Anthony489 (G8FMQ)

Just to add a different take on the P0638 code. This comes up very occasionally on my 2010 reg van (probably 2009 build as it has the early throttle body) usually after not being used for a while (motorhome), this occurred last month five minutes away from an MOT appointment

Each time I've successfully cleared the code and I've also checked the throttle body flap for free movement.

I've concluded that the fault in my van is thrown up due to the EGR solenoid electrical connection getting damp as it sits just below the infamous scuttle joint. Once the van is in use again the engine heat dries the solenoid.

I'll test this theory this winter by covering the solenoid up.

Thanks for the information Anthony489.

I suspect the 3 Volt I was seeing was due to using a high impedence multimeter rather than an 'AVO'. Definately there was no 12 volts on the Throttle body connector, but as Fuse F11 was blown this would explain why.

Hopefully attached are two pictures of the internals of the throttle body electronic module. Both by the look (and smell) there has been serious burning which is probably why the fuse blew !. Also found a small label on the throttle body which said 'Re-furbished' so immediately suspicious which is why I have changed the body to a new one which has the servo motor rather than a stepper motor. Short 'MOD' wiring also fitted as the new body has the six pin connector rather than the old four pin on the original body.

Waiting for the replacement EGR solenoid to arrive (don't you love Ebay delivery dates) and will check with everything disconnected first to definately eliminate wiring problems.
Hopefully will be up and running again some time next week and will report back. If nothing else it has been a good learning excercise on Ducato wiring !.


Martin, GM6VXB

Finally the EGR solenoid valve arrived today.
Two minutes to fit and another couple to remove old OBD fault codes.
Started up and checked and very pleased to say no fault codes !!.

Why the valve had failed I do not know. As I said earlier, the throttle body had a small sticker on it saying 're-furbished' so looks like whoever did the job did not do a good one. Suspicion says the throttle body somehow caused the EGR solenoid to fail but not definate.


So thanks for the help, no doubt something else will go wrong on the motorhome.

Martin, GM6VXB

An update to my post #5 :

This year the EML came on more frequently with the same code of P0638 and I therefore fitted a new EGR solenoid valve but sadly this didn't cure the fault and closer inspection suggests that this valve is actually fairly well protected from water leaks through the scuttle.

I've taken the van to a local workshop that specialises in motorhomes (so the owner is fairly familiar with Ducato's) to have a new throttle body fitted. He assured me this job takes about an hour (and indeed only charged me an hour's labour!)

His code reader is much more sophisticated that my ebay special and registered a 'throttle body short to ground' fault so I'm fairly confident the problem is now sorted.

The workshop trades as DEM Motorcaravans and is located in Rackheath near Norwich.