2008 Fiat Scudo Overboost error code
Discussion
Arrrrgggghhhhhhhhhh
I'm new here so thanks for having me and apologies for starting with a Fiat 2.0Hdi problem.
I'm getting Limp mode with error code P0234 (Turbocharger"A" Overboost ) no other codes when all is connected, I've got an ODB reader with live data (limited) which shows my MAP being 104Kpa at idle, acclerating in 3rd up a hill (repeated route to test) trips into Limp Mode with P0234 and way over 220Kpa. So its not releasing pressure to be expelled by the exhaust)
So i've checked the wiring,the vacuum hoses, the vacuum pump output and replaced the Boost Solenoid ( the old one was very draggy) all to no avail.
I pulled the turbo out yesterday (no easy task on a Scudo) give it a good clean, found a sticky Vane. Reassembled it and it's working very smooth (the vanes are moving freely with no resistance). I tested the actuator using a vacuum pump and it works OK(ish), its a bit wobbly and the first 5mm or so is loose ( when not unde pressure), it takes a bit of pressure to get it going (about .3bar , reaching maximum at about .8bar).
I'm at a loss as to what to do to be honest, my instinct its the Vacuum Actuator is at fault as Its very slow to do anything (I've also observed it on the van during start up and it barely moves.
Anybody got any help they can throw my way?
I'm new here so thanks for having me and apologies for starting with a Fiat 2.0Hdi problem.
I'm getting Limp mode with error code P0234 (Turbocharger"A" Overboost ) no other codes when all is connected, I've got an ODB reader with live data (limited) which shows my MAP being 104Kpa at idle, acclerating in 3rd up a hill (repeated route to test) trips into Limp Mode with P0234 and way over 220Kpa. So its not releasing pressure to be expelled by the exhaust)
So i've checked the wiring,the vacuum hoses, the vacuum pump output and replaced the Boost Solenoid ( the old one was very draggy) all to no avail.
I pulled the turbo out yesterday (no easy task on a Scudo) give it a good clean, found a sticky Vane. Reassembled it and it's working very smooth (the vanes are moving freely with no resistance). I tested the actuator using a vacuum pump and it works OK(ish), its a bit wobbly and the first 5mm or so is loose ( when not unde pressure), it takes a bit of pressure to get it going (about .3bar , reaching maximum at about .8bar).
I'm at a loss as to what to do to be honest, my instinct its the Vacuum Actuator is at fault as Its very slow to do anything (I've also observed it on the van during start up and it barely moves.
Anybody got any help they can throw my way?
Thanks for the replies and sorry for taking so long to reply myself ( the forum wouldn't let me).
Yeah it's a bit turbo, since my first post I've replaced the turbo as there was little damage to it and the actuator wasn't working correctly. Unfortunately I'm still getting the p0234 overboost error and limp mode.
There a no breaks in the vacuum lines but the fitting onto the actuator isn't as tight as the other fittings, could it be leaking out of there as the vacuum is applied?
Yeah it's a bit turbo, since my first post I've replaced the turbo as there was little damage to it and the actuator wasn't working correctly. Unfortunately I'm still getting the p0234 overboost error and limp mode.
There a no breaks in the vacuum lines but the fitting onto the actuator isn't as tight as the other fittings, could it be leaking out of there as the vacuum is applied?
Check the MAF. When I had a lot of hassle with a Fiat, that was the problem, although all the error codes suggested a turbo problem.
https://www.pistonheads.com/gassing/topic.asp?t=12...
https://www.pistonheads.com/gassing/topic.asp?t=12...
Spev11 said:
Thanks for the replies and sorry for taking so long to reply myself ( the forum wouldn't let me).
Yeah it's a bit turbo, since my first post I've replaced the turbo as there was little damage to it and the actuator wasn't working correctly. Unfortunately I'm still getting the p0234 overboost error and limp mode.
There a no breaks in the vacuum lines but the fitting onto the actuator isn't as tight as the other fittings, could it be leaking out of there as the vacuum is applied?
Test and find out.Yeah it's a bit turbo, since my first post I've replaced the turbo as there was little damage to it and the actuator wasn't working correctly. Unfortunately I'm still getting the p0234 overboost error and limp mode.
There a no breaks in the vacuum lines but the fitting onto the actuator isn't as tight as the other fittings, could it be leaking out of there as the vacuum is applied?
forum locked out again 
anyway, its quit difficult to access the actuator and the hose as its down between the back of the engine and the bulkhead( its all done by feel).
I've pulled the vacuum hose off and there's a difference in size from one end of the rubber piece (the hose has a rubber section at each end of an aluminium pipe) so im waiting for some vacuum hose to replace them and see if that helps.I did try driving without the MAF as sunbeam alpine suggested may be the problem but to no avail.
While I wait for the hose anybody want to point me in any other direction? Most of the other common problem (blocked intakes etc) seem to cause low boost rather than overboost but I'm open to any suggestions
again thanks for your help
anyway, its quit difficult to access the actuator and the hose as its down between the back of the engine and the bulkhead( its all done by feel).
I've pulled the vacuum hose off and there's a difference in size from one end of the rubber piece (the hose has a rubber section at each end of an aluminium pipe) so im waiting for some vacuum hose to replace them and see if that helps.I did try driving without the MAF as sunbeam alpine suggested may be the problem but to no avail.
While I wait for the hose anybody want to point me in any other direction? Most of the other common problem (blocked intakes etc) seem to cause low boost rather than overboost but I'm open to any suggestions
again thanks for your help
its just vacuum from the vacuum pump, theres a hose from the pump to the N75 Solenoid, then this hose from the N75 to the actuator, im trying to wrap my head around whether there is vacuum at idle or whether it as applied to reduce boost, i will add its difficult to determine when the vacuum is being applied/shut off as my manual gauge has no way to be fitted and viewed whilst the engine is running at anything other than idle. I've got some t-pieces and some extra hose coming so I can rig it up to be in the van when i'm driving it 
Edited by Spev11 on Friday 26th October 14:09
revs mean little.
As load/demand rises, then you would expect the engine to make more boost.
But yes, a vacuum gauge installed on the line to the actuator would be a good start.
Of course....it still sounds like you've done no proper interrogation of the ecu to even see what boost targets are set, and determine whether it is overboosting and under what circumstances etc
As load/demand rises, then you would expect the engine to make more boost.
But yes, a vacuum gauge installed on the line to the actuator would be a good start.
Of course....it still sounds like you've done no proper interrogation of the ecu to even see what boost targets are set, and determine whether it is overboosting and under what circumstances etc
engine load makes more sense yes
I don't have the means to interrogate the ECU to find out what the activation levels are, the diagnostic (a D900) i have is quite basic but does have live data (but only shows load, revs, MAP and MAF). If I were to at least fit a vacuum gauge it would show me at what revs/load/MAP setting the vacuum was being applied/shut off wouldn't it?
I'd happily invest in something a little better if someone could point me in the right direction
I don't have the means to interrogate the ECU to find out what the activation levels are, the diagnostic (a D900) i have is quite basic but does have live data (but only shows load, revs, MAP and MAF). If I were to at least fit a vacuum gauge it would show me at what revs/load/MAP setting the vacuum was being applied/shut off wouldn't it?
I'd happily invest in something a little better if someone could point me in the right direction
A vacuum gauge will at least tell you the boost solenoid, vac pump etc etc are all working and give some indication as to the integrity of all the vac lines ( ie leaks or not )
As to how much vacuum you should see at the actuator however....not a clue on that one. But at least if there is some...a reasonable amount and it is indeed varying with load, would be a good indicator that all the control strategies are working.
Using the likes of this https://www.sykes-pickavant.com/products/compressi...
Which could double as your gauge and a means of leaking or applying vac to the same lines would give some other testing options. Usually available from ebay etc for around £80-90
Maybe a bit much for a one off, but still a handy tool
Diagnostic tools/software more specific to your vehicle should yield more information....generic OBD as you've seen only gives the basics.
As to what will give the info you need however I dont know, not sure who offers dealer style diagnostics for them.
You could call and ask the likes of Gendan to see if any of theirs would be at that level. If they arent, then they maybe are not worth looking into.
https://www.gendan.co.uk/category_161.html
But even for the above vac test, you'd want to be seeing wastegate control duties at the ecu to see what it is actually asking/telling and then you could view via boost and the vac gauge if this is then happening as expected.
Failing that, a meter on the boost solenoid ( duty cycle probably best ) to see what it is being told, and again is there a corresponding change in boost etc.
As to how much vacuum you should see at the actuator however....not a clue on that one. But at least if there is some...a reasonable amount and it is indeed varying with load, would be a good indicator that all the control strategies are working.
Using the likes of this https://www.sykes-pickavant.com/products/compressi...
Which could double as your gauge and a means of leaking or applying vac to the same lines would give some other testing options. Usually available from ebay etc for around £80-90
Maybe a bit much for a one off, but still a handy tool
Diagnostic tools/software more specific to your vehicle should yield more information....generic OBD as you've seen only gives the basics.
As to what will give the info you need however I dont know, not sure who offers dealer style diagnostics for them.
You could call and ask the likes of Gendan to see if any of theirs would be at that level. If they arent, then they maybe are not worth looking into.
https://www.gendan.co.uk/category_161.html
But even for the above vac test, you'd want to be seeing wastegate control duties at the ecu to see what it is actually asking/telling and then you could view via boost and the vac gauge if this is then happening as expected.
Failing that, a meter on the boost solenoid ( duty cycle probably best ) to see what it is being told, and again is there a corresponding change in boost etc.
Cheers for all the info, ive just made up some vacuum hoses to test the various inputs and outputs.
Ive had a look at diagnostic and few people support the siemens ECU in the PSA vans, i've found a cable and some software that can read the ecu so as soon as that arrives i'll be reading that.
Many thanks for all your help and i'll update you when something happens
Ive had a look at diagnostic and few people support the siemens ECU in the PSA vans, i've found a cable and some software that can read the ecu so as soon as that arrives i'll be reading that.
Many thanks for all your help and i'll update you when something happens
My Lexia3 has finally arrived, getting the laptop sorted now to check the ecu out.
I replaced the Solenoid with the correct one and its all been ok for the last week or so until tonight driving home and P0234 popped up on my diagnostic so I'm back at the start again. Once i've got the lexia installed and working I should be able to see whats going on
I replaced the Solenoid with the correct one and its all been ok for the last week or so until tonight driving home and P0234 popped up on my diagnostic so I'm back at the start again. Once i've got the lexia installed and working I should be able to see whats going on
While im waiting for the install of lexia diag on my laptop (its deathly slow) i've been running vac tests on the van and checking some other things.
So far I've discovered that :-
a.The solenoid works when I apply power to it (no vacuum allowed with no power, vacuum allowed with power)
b.the solenoid is allowing boost all the time ( vac gauge shows 1 bar regardless of load/revs etc)
c.the solenoid doesn't shut down the vacuum at any point that I can see.
d.If I introduce a bleed/leak to the hose from the solenoid to the actuator the van runs, I have boost but it doesn't drop into limp mode (its not as mental quick as it was when it was keeping the actuator open)
e.Hopefully once I get this diagnostic software running I'll be able to see why the solenoid isn't being switched)
as for point d is there any danger to the van if i run it in this mode whilst I find out what the problem is? I'm not intending to leave it like this but I need to use the van for work (short journeys for now until I find a solution)
So far I've discovered that :-
a.The solenoid works when I apply power to it (no vacuum allowed with no power, vacuum allowed with power)
b.the solenoid is allowing boost all the time ( vac gauge shows 1 bar regardless of load/revs etc)
c.the solenoid doesn't shut down the vacuum at any point that I can see.
d.If I introduce a bleed/leak to the hose from the solenoid to the actuator the van runs, I have boost but it doesn't drop into limp mode (its not as mental quick as it was when it was keeping the actuator open)
e.Hopefully once I get this diagnostic software running I'll be able to see why the solenoid isn't being switched)
as for point d is there any danger to the van if i run it in this mode whilst I find out what the problem is? I'm not intending to leave it like this but I need to use the van for work (short journeys for now until I find a solution)
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff