Technical Double MAP failure ..

Shadeyman · Jun 7, 2011

Following my daughter south bound M6 last night, we slowed down for 2 HGV, one crawling passed the other at 60mph(why do they bother?).

My daughter accelerated to about 80mph then slowed to 50mph pulling into the inside lane as she did.

My phone rings, its her other half Craig. Engine warning light on the dash so we pull in at the next services.

I had left my Dell PDA in the glovebox, has FESMobile on it. Connected to her car and P0235 error (supercharger) was stored so I had a quick look under the bonnet, nothing obvious so I cleared the fault and we carried on homeward.

A few miles later she's a few cars infront of us and my phone rings again, P0235 was back. I put my foot down to catch up to her and guess what?
Our car lost power and showed the engine warning on the dash.

There wasn't much traffic so we pulled onto the hard shoulder, hazards blazing.

Both cars had the same error, P0235 Supercharger ....

Quickly cleared the errors and drove home at 60mph behind the HGV's we overtook earlier.

Hooked up my laptop to both cars this morning after taking them for a quick blast down a local dual carriageway, sure enough the dreaded P0235 error was there on both cars.

I'm guessing we both need new MAP sensors as I can't find anything else that could be causing the problem?

Anything you guys think I should try before purchasing 2 new MAP sensors?

Deckchair5 · Jun 7, 2011

Morning Shady
I have
[FONT=&quot]P0235 as Turbocharger Boost Sensor A Circuit Malfunction
is that what you have?
[/FONT]

Shadeyman · Jun 7, 2011

Yes Deck's.

Can't believe both cars MAP sensors failed within minutes of each other ..

Oh and good morning to you too.

Deckchair5 · Jun 7, 2011

No, they're very robust and often get changed when there's nothing wrong with them. As you both experienced the same fault doing the same thing and you are experimenting with fuels then it would be foolish not to consider the common factor but just how that could effect the MAP output I don't know

MAPs are expensive so it's well worth getting a hand vacuum pump so you can test it and check the outputs if you're messing about them quite a bit, saves quite a few wasted bucks. I don't know whether FES shows the MAP readout like it does on petrol engines, maybe there's freeze frame data to be explored which will give the trigger data?

Shadeyman · Jun 7, 2011

Deckchair5 said:
No, they're very robust and often get changed when there's nothing wrong with them. As you both experienced the same fault doing the same thing and you are experimenting with fuels then it would be foolish not to consider the common factor but just how that could effect the MAP output I don't know

Using Bio-Diesel in my car thats professionally produced to BS EN 14214 is not what I call "experimenting" but I see your point.

My daughter uses what ever diesel she finds at the nearest garage, usually Bio but not always.

Agreed, Bio is a common factor but I don't see how it could effect the MAP Sensor. Our car has been running perfectly on it for over 8 months.
My daughters car had a brand new MAP sensor fitted when I purchased the car last November, not sure how old ours is?

Deckchair5 said:
MAPs are expensive so it's well worth getting a hand vacuum pump so you can test it and check the outputs if you're messing about them quite a bit, saves quite a few wasted bucks. I don't know whether FES shows the MAP readout like it does on petrol engines, maybe there's freeze frame data to be explored which will give the trigger data?

"vacuum pump"? I thought the MAP measured an increase in pressure(boost) not a drop in pressure(vacuum)?

MAP sensor from Fiat is £35 so it wont break the bank but no point replacing it if its not the MAP causing the problem.

Is there a way to test it, there is a MAP read out in FES for the JTD?

Deckchair5 · Jun 7, 2011

MAP on petrols measure the pull ie vacuum. Your MAP may well measure the boost pressure, either way you want something to simulate that pressure so you can read off its voltage output

MAP reported faults are often plausibility errors being spotted ie the "MAP can't be at that value when other sensors are reporting these values"

Blocked or split pipes are a possibility

I'm not using FES so can't tell you what parameters it's capable of recording but i'm sure MAP output is in there on petrols. Best test is to simulate the pressures and check the output figures or study the diagnostics running data to see what's happening

Shadeyman · Jun 7, 2011

Deckchair5 said:
you want something to simulate that pressure so you can read off its voltage output

Deckchair5 said:
I'm not using FES so can't tell you what parameters it's capable of recording but i'm sure MAP output is in there on petrols. Best test is to simulate the pressures and check the output figures or study the diagnostics running data to see what's happening

I have a airbed pump, produces about 5psi. If I were to put the nossle of the pump over the sensor hole while the car was runing and use FES to monitor voltage and pressure from the MAP. I don't suppose you know what readings I should expect to see if the MAP is good and what readings should I expect if the MAP is bad. Example: 900mb - 9v?

Deckchair5 said:
MAP reported faults are often plausibility errors being spotted ie the "MAP can't be at that value when other sensors are reporting these values"

Blocked or split pipes are a possibility

I've looked three times now and can't see anything, split etc. Going to use an old gas fitters trick and spray all the positive pressure ducts feeding the engine with a 40 - 60 mix of fairy liquid and water. Any escaping air will produce a bubble I can see.

Oakley28 · Jun 7, 2011

I wish you would service my car shadey, you seem to know your stuff and my car could use thorough service by someone who knows how to problem solve. You think Fiat would but I take it there every year and they dont listen to what I tell them is wrong and say there's no power loss or no split pipes or no loud revs etc etc etc you get the point.

They are useles....

Deckchair5 · Jun 7, 2011

The MAPs specifications tend to use Kpa v voltage so with mine 100Kpa= 4v change or 1inHg = 1v but you'd have a job relating that to an airbed pump

If you pick up the part no you may be able to google a specs sheet

With mine then they start at atmos press and go down to measure vacuum and with yours I guess they start at atmos and go up to show positive pressure

No freeze frame data? Diagnostics running data prog may be the best way forward for you

hanzs · Jun 7, 2011

Shadeyman: You should log livedata "boost pressure" vs. "desired boost pressure. Probably you will see that "boost pressure" is higher than "desired boost pressure" and this trigger the fault P0235.
This common fault on JTDs, check solenoid, hose-pipe to turbo... see this: https://www.fiatforum.com/stilo-guides/224083-stilo-jtd-boost-solenoid-valve-resite.html
There is also possibility, that turbo has stuck bladings in one position and they do not move now...

Shadeyman · Jun 7, 2011

Here's the data from a quick drive up then back down a nearby dual carriageway.

Both runs produced the engine fault when I changed from 3rd to 4th.

I've tried to show this on the graphs. The dark blue line is vehicle speed, A = 2nd gear
B = 3rd gear
C = 4th gear and engine fault.

I still suspect the MAP but any advice/opinions would be very welcome.

Shadeyman · Jun 7, 2011

As a comparison, here's the same data from September 2010 when I brought the car.

hanzs · Jun 7, 2011

Shadeyman: As you can see on the graph - output of your turbocharger is really high - over 2500mBar!! When you bought the car the maximum was 2200-2300 mBar and desired in both cases is about 2100mBar.
I dont think this is faulty MAP - because MAP output varies between 1100 up to 2500mBar. But you can do simple check - when engine off, key on - see the MAP value "boost pressure" and should be atmosferic pressure about 1000mBar.

keviwal · Jun 7, 2011

Stu,
I kept getting P0235 and spent days arsing around with MAP/ pipes etc etc and in the end i changed the boost valve as i couldn't think of anything else and yes havent seen the fault since.

Cheers for now

Shadeyman · Jun 7, 2011

hanzs said:
But you can do simple check - when engine off, key on - see the MAP value "boost pressure" and should be atmosferic pressure about 1000mBar.

Took two reading.

1. Ignition on engine off - 978mb

2. Ignition on engine on - 1001mb

I've attached screen shots of FES data and one of todays atmospheric pressure reading taken at 1am. My weather station is showing 601mb.

So is the MAP ok, think I might replace it anyway.

keviwal said:
Stu,
I kept getting P0235 and spent days arsing around with MAP/ pipes etc etc and in the end i changed the boost valve as i couldn't think of anything else and yes havent seen the fault since.

Cheers for now

Already swopped it with a spare I have and with the one on my daughters car which is fine now since I removed and cleaned the MAP and MAF sensors.

hanzs · Jun 7, 2011

So when MAP is ok and solenoid was changed, you should try to test VNT system of your supercharger:
try to connect and disconnect vacuum to cylinder and see if rod is moving...

Shadeyman · Jun 7, 2011

Started the car and video'd it with my phone.

[ame="http://s296.photobucket.com/albums/mm189/Shadeyman67/?action=view&current=MOV00163.mp4"]MOV00163.mp4 video by Shadeyman67 - Photobucket@@AMEPARAM@@http://vid296.photobucket.com/player.swf?file=http://vid296.photobucket.com/albums/mm189/Shadeyman67/MOV00163.mp4@@AMEPARAM@@vid296@@AMEPARAM@@296@@AMEPARAM@@mm189/Shadeyman67/MOV00163@@AMEPARAM@@mp4[/ame]

hanzs · Jun 7, 2011

hmm, hmm, I not sure - the movement looks jerky and I think it should move more...

Shadeyman · Jun 7, 2011

hanzs said:
hmm, hmm, I not sure - the movement looks jerky and I think it should move more...

Your right it should move more so I decided to remove the 2 lengths of thin pipe connected to the boost valve again to do a bubble test on them using my airbed pump and a bowl of soapy water.

BINGO!

2 small holes next to the boost valve I missed when I checked the first time.

Cut off the faulty part with holes in, reconnected it.

The car now pulls hard and no engine warning.

I'll connect FES in the morning so we can compare the data.

hanzs - Thank you very very much for your help, it's very much appreciated.

FIAT FORUM 1 - FIAT DEALER 0

Shadeyman · Jun 8, 2011

Deckchair5 said:
MAP reported faults are often plausibility errors being spotted ie the "MAP can't be at that value when other sensors are reporting these values"

You were right Deck's ...

Technical Double MAP failure ..

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