Do I have conclusive evidence

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Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 9:34 am

I have been absent for many months, but now I've reached a point where I could do with second opinions from the members of the forum, let me explain...

7 months ago, I did a job on a fiat ducato van 2007 model fiat ducato maxi X250, 120hp multijet engine, 2.3JTD. Engine code F1AE0481D

Van came in with EML on, recently purchased by customer. Plugged in texa navigator and got; P0638 - Throttle solenoid valve control - Short to ground

Carried out a physical inspection of the TB and found the electric actuator completely seized due to water ingress, and one of the drive pawls onto the butterfly shaft broken off - strong case for a replacement part.

Obtained from fiat a re-furbished part (the only option they could offer at the time - an old casting with new moving parts and electical actuator), fitted the part, cleared the code and sent the man on his way. Within a month he had driven the van to corfu, and was later to report that soon after arriving in Greek territory the EML was coming back on intermitently with some hesitance when EML was on. A Greek garage deemed it to be down to 'sub-standard' Greek fuel, and suggested some addative or other. Long story short the van was used very little once actually on Corfu "perhaps four or five times" - quote unquote.

About 1 month ago the guy is back in the UK and fills up in Dover, the van drives all the way back here to the North West with no issue - which tends to back up the poor fuel angle. For a further week its all good, then the EML is back, and the guy brings it into me.
Well imagine my suprise when I plug in to find P0638 - Short circuit to ground, the exact same fault - only this time its not a current fault, only held in the memory.

My texa is capable of commanding the TB for a function check, which I carried out, and couldn't fault and have got the trace below:
actuator test pass_1.jpg



A
Last edited by Avdr on Thu Jun 13, 2013 10:29 am, edited 1 time in total.
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Re: Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 9:48 am

At this point it seems time to explain the TB a little more; Its a four wire device.
Pin 1 = Ecu controled PWM ground
Pin 2 = Vbatt supply via some relay/fuse
Pin 3 = Ground for position feedback circuit
Pin 4 = Position feedback signal

Ordinarilly the buttefly is fully open, by virtue of a spring. The ECU commands it to close via PWM and position is fed back via a potentiometer within the gubbins.

Ok so, so far no fault found. For 3 days it went on like this, everytime I looked at the van it was good as gold.

Yesterday it finally acted up, from a hot start the EML immediately illuminated - with no loss of driveability though. I drove back to the workshop and without turning the van off, plugged the texa in. Now I found the same P0638 code, cycling between stored and current every few seconds, I quickly got the scope out and had a looksey at the four wires to the TB.

I had already establised that the 12v feed (pin 2) was most unlikely to be the cause of the problem - as I have no other fault codes, and it seems reasonable to expect that wire to feed multiple 12v items. Have no wiring diagram as yet for this vehicle.
Anyway it quickly was proven with the scope that the 12v feed was ok, see trace below, taken with the van idleing it shows an overview of the dropout on the PWM line - which is very consistant

TB dropout 1s_01.jpg


and also at 10ms, this one caught the exact moment it dropped out
TB dropout 10ms_13.jpg
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Re: Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 10:02 am

After some data had been collected I decided it was time to shut the engine off and return to KOEO, I qucikly cycled the key off then back - the ECU did not power down inbetween.

I tried again to run the TB actuator test - only to find it failed, so I manually verified the butterfly wasn't stuck and upon confirming this I progressed to move it with my finger through its full 90 degree sweep, all ok and feedback circuit responding correctly.

I still had the same dropout charecteristic, as shown below in the picture
TB dropout 500ms KOEO with manual short to ground_1.jpg


Afrter a pause, I decided to manually short the PWM to ground, expecting the valve to move fully closed if it was able to, the result is shown in this picture - nothing happened with the valve but the PWM was pulled low:
TB dropout 500ms KOEO with manual short to ground_2.jpg

I was suprised to see no voltage drop on the feed wire, and by now I'm seriously thinking the actuator is open circuit inside.
Anyway I had come to the end of any tests I felt I could do now, I decided to unplug the TB and measure the resistance across the actuator with the DMM, ended up changing my mind about the resistance test (not sure why) but inserted the break out leads between TB connector and plug, and fired the van up again - to my frustration it was all back to normal and working correctly again.
I tried one last test, which was bascially repeating the earlier experiment of manually shorting the PWM to ground, and this time a voltage drop was observable on fed wire, though the valve didn't move to fully closed as I had expected it to.
TB normal KOER manual short to ground_06.jpg
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Re: Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 10:27 am

psadata files in order of pictures
actuator test pass.psdata
(2.27 MiB) Downloaded 211 times


20130613-0001.psdata
(2.02 MiB) Downloaded 202 times


20130613-0001.psdata
(1.15 MiB) Downloaded 202 times






20130613-0001.psdata
(1.56 MiB) Downloaded 189 times


The Fiat angle is as follows. I can take the van into them and they will plug it in, if they find the TB faulty I can have another one and no charge for the diagnostic test. If they find it working OK, I owe them for the diagnostic test.
They are booked up solid until thursday 20th june, and even then its an intermittent fault anyway. I'm reluctant to drive out there with it not acting up, also the customer wants to see some action.
So I'm asking, do others agree that I have a fault TB, or am I missing something?

Thanks
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Re: Do I have conclusive evidence

Postby KimAndersen » Thu Jun 13, 2013 12:54 pm

Hi

I must say you have done a very extensive effort to solve this problem.

One thing I would like to know, is there any problems concerning the engine performance such as the engine are misfiring ?

The reason that I´m asking is that you are only mentioned the EML are on.First I would like to say that i have no ide what is causing this type of problem. The only thing that I have found that may be of some interest regarding your problem is from a document from IVECO that covers this type of engine.

IVECO_F1AE0481B.jpg


I´m wondering about this could upset the ECU if the power supply sometimes are disconnected to soon before it could save the informations in the ECU or if you switch the ignition key on and off to quickly.

It is just a thought. :wink:

Regards
Kim
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Re: Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 1:06 pm

Just measured the resistance of the valve, the engine has been run upto temp from a cold start with no problems, and fauld code remained stored not current. Resistance across pins 1&2 is 1.2 Mohm. Stable too. There must be some electrical gubbins in the actuator beyond just a coil and pot, there must also be a voltage reg to bring the 12v feed down to 5v for the feedback pot. Cannot say what more there is though.
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Re: Do I have conclusive evidence

Postby Avdr » Thu Jun 13, 2013 2:48 pm

Hi Kim, there are no problems at all with the vans performance normally. Its a perfect drive. One final test I plan to carry out is a current check to the actuator. I will report back after having done that test.
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Re: Do I have conclusive evidence

Postby KimAndersen » Fri Jun 14, 2013 10:57 am

Hi Advr

Not sure that you can use the resistance check to anything, because the measurement are made through some chip components and not through the motor phase wiring alone. The only thing you can rule out with a measurement of 1 Mohm is that it´s not short circuit.

Regards
Kim
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Re: Do I have conclusive evidence

Postby Avdr » Fri Jun 14, 2013 7:37 pm

I only mention the resistance as I found a fiat training guide that was designed to breif tech's on the new range of engines and it included a paragraph on this throttle body. It states the
'Series and contact resistance' as 1kOhm +/- 0.4kOhm.
Here is a picture of the passage:
tb.JPG



link here to the entire document: http://library.docent.isvor.it/upload/l ... ase_GB.pdf

page 64.

I did grab a current trace from the valve, although at the time it was functioning correctly. Its not very easy on the eye though

peo7 ulm koeo actuator 20ms plus current.psdata
(1.17 MiB) Downloaded 200 times


EDIT: Actually, looking at that info with fresh eyes, it seems more related to the POT than than the actuator, and is pretty irreleavant.
Andy
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Re: Do I have conclusive evidence

Postby Avdr » Mon Jun 17, 2013 2:14 pm

two more traces with current, taken this morning when the valve was faulty again.
Is anybody in agreement that the valve is indeed at fault? I'm getting to the verge of replacing it out of my own pocket but want to be certain its £300 well spent.
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