Technical My Findings with P0235 Error Code

[DeanF]

Stilo 1.9 Jtd 2003
I had the Engine Failure Error & 3 Beeps Etc, This appeared after going through Floods.
The overboost valve had never been relocated so assumed that.
Dried the overboost valve out & relocated, For a few days no error but then it came back & performance was intermittent.

Had the error codes read off the Ecu & P0235 Overboost was there.
Ordered a new overboost valve & fitted Last Mon.17th Dec.
Since then No error/3 Beeps but the Performance did feel flatter at times ( I just thought it was me !!)

Tonight coming home V Cold -1.5 Deg Start to overtake 4th gear & Engine Failure 3 Beeps, So it would seem the overboost valve is not at fault !.

I again checked for leaks Etc on Hoses but could not find any.
I unplugged the Egr valve & drove the car . No errors but the car did not have the usual surge of power when it is running Ok.

Re-plugged the Egr valve But this time blanked off the Egr so it was sealed off completely. Drove the car, Again not the usual surge of power but no Engine failure error or Beeps.

So i appear to be left with 2 items that would make performance inconsistent & cause overboost !!.

Faulty EGR Valve or Faulty Wastegate Actuator ??

Can i drive around with the Egr Blanked off for a few days to see if the error re-appears ? If it does this can only surely mean the wastegate actuator is at fault !!.

If it was the manifold Pressure Sensor that was faulty , This wouldn't make the power flat/inconsistent as it only Monitors pressure/warns, It does not bleed boost off Etc so the car would drive consistently below the warning threshold ??

Ideas / Input ??

Cheers

Dean

 

[Argonought]

Tonight coming home V Cold -1.5 Deg Start to overtake 4th gear & Engine Failure 3 Beeps, So it would seem the overboost valve is not at fault !.

These are classic symptoms of a leak/split/puncture in the tubing either side of the overboost valve (since you know the valve is OK)

Sure you haven't missed something :chin:

Blocking the EGR valve (so it can't function) should not affect performance (just economy)

 

[T14086]

Blocking the EGR valve (so it can't function) should not affect performance (just economy)

and emissions/cylinder temp.

 

[DeanF]

These are classic symptoms of a leak/split/puncture in the tubing either side of the overboost valve (since you know the valve is OK)

Sure you haven't missed something :chin:

Blocking the EGR valve (so it can't function) should not affect performance (just economy)

Im Quite certain that the pipes are sound, Although i will re-check again.
Doesn't the Egr lean off the Mixture slightly when operational ? If it is then blocked off you will use more fuel & in theory not have as big a bang for your buck, So feel Smoother !!??

So if your saying it should not affect performance that then again points a the Wastegate actuator Or Hoses Etc.

What is the Black box for on the back of the Engine (Between Bulkhead & engine) Where wuite a few vacum hoses connect to ???

Cheers

Dean

 

[DeanF]

and emissions/cylinder temp.

Hi Mr Mod.
The error appears just as you start to load the engine in higher gears. As a result of this i was not planning on driving the car V hard,
On Wide Open Throttle isn't the Egr valve closed (Supposed to be) anyhow, So no gases get cooled from the water jacket that wraps around the Egr/Turbo Pipe ??.

Cheers

Dean

 

[D4nny8oy]

The standard way of diagnosing a faulty EGR valve is blanking it off- if the fault is still present, then the EGR is not the cause (when faulty, an EGR valve will normally 'bleed' air off the Turbo and creates 'lag' until the engine revs and exhaust airflow rise enough to overcome this- usually at 3/3.5K rpm).

How did you attach the heat-shrinked vacuum hoses to the new overboost valve? Any vacuum leak here will affect the amount of actuator movement, and therefore available boost.

A 'Live' run with a Fiat Examiner connected under the Recorder function is the ideal way of monitoring the overboost pressure/ air flow/ etc under all conditions to ensure the figures are correct.

 

[D4nny8oy]

Hi Mr Mod.
The error appears just as you start to load the engine in higher gears. As a result of this i was not planning on driving the car V hard,
On Wide Open Throttle isn't the Egr valve closed (Supposed to be) anyhow, So no gases get cooled from the water jacket that wraps around the Egr/Turbo Pipe ??.

Cheers

Dean

Wikipedia once again-

http://en.wikipedia.org/wiki/EGR#EGR_in_diesel_engines

 

[jostheboss]

Someone at work mentioned something about the coolant temp sensor being a cause to similar symptoms - anyone heard anything about this, cus when the RAC plugged in, there machine said it was 200 degrees - he just assumed his machine was faulty, not the car....

 

[DeanF]

The standard way of diagnosing a faulty EGR valve is blanking it off- if the fault is still present, then the EGR is not the cause (when faulty, an EGR valve will normally 'bleed' air off the Turbo and creates 'lag' until the engine revs and exhaust airflow rise enough to overcome this- usually at 3/3.5K rpm).

How did you attach the heat-shrinked vacuum hoses to the new overboost valve? Any vacuum leak here will affect the amount of actuator movement, and therefore available boost.

A 'Live' run with a Fiat Examiner connected under the Recorder function is the ideal way of monitoring the overboost pressure/ air flow/ etc under all conditions to ensure the figures are correct.

I attached the new hoses with Jubile type clips, So no evident leaks, The car did have moments when it felt really laggy, (Pre Egr blank off) But with it blanked off it does not have the usual surge, Much smoother power delivery !!! As of yet no beep Beep Error

Cheers

Dean

 

[Argonought]

.....cus when the RAC plugged in, there machine said it was 200 degrees - he just assumed his machine was faulty, not the car....

My ELM interface always reports 215C to be precise

 

[DeanF]

Well, Since blanking the Egr off i have had the error again
I have since purchased a fitted a new Manifold Pressure Sensor. The part number has V recently changed & jumped from £23.49 to £53.67 & is physically bigger the the sensor i removed.. The chap at the dealers said they sell loads of the Sensors, Cars come in with the P0235 Error ( It just relates to Overboost & not specifically to the Overboost Valve) They fit one of these, It goes away, 12 Months later it's back, They Fit one !! You get the picture..

Lets see what happens now !!!

Dean

 

[bozzy]

Well, Since blanking the Egr off i have had the error again
I have since purchased a fitted a new Manifold Pressure Sensor. The part number has V recently changed & jumped from £23.49 to £53.67 & is physically bigger the the sensor i removed.. The chap at the dealers said they sell loads of the Sensors, Cars come in with the P0235 Error ( It just relates to Overboost & not specifically to the Overboost Valve) They fit one of these, It goes away, 12 Months later it's back, They Fit one !! You get the picture..

Lets see what happens now !!!

Dean

Dean, how difficult is it to do, I intend to fit one and move my O/B valve at the same time?

 

[DeanF]

Dean, how difficult is it to do, I intend to fit one and move my O/B valve at the same time?

Hi Bozzy, Not difficult at all.

MP Sensor, Is about half way accross the inlet manifold on the Bulkhead side, Quite easily identifiable by being the only black sensor that screws directly into the inlet manifold. Mine was held in by a Torx bit type bolt, But i have also seen them held in with a 10mm headed bolt ( I think these are the ones that have already been swapped & the owners have junked the Torx Bit bolt for ease).
Once the engine cover is removed access is not to bad, I put the Torx bit in place & then used a 8mm spanner accross it flats to undo ETc. Once the bolt is unscrewed, the sensor just pulls out, Be prepared for it to be full of Soot & Mank !! Mine was. Reverse for assembly Etc.

The overboost relocation was not to bad either, Jack the car up on the near side,remove the Near side plastic splash guard,(The one that the main sump guard fastens to) & the main sump spalsh guard.This gives you access to unbolt the overboost valve using a 10mm socket on a long extension bar, i think i unplugged it first also to get better accces to the top nut.

Once un-bolted i had to snip the hoses as they would not pull off. Re-sight the valve on the battery box (I used two meaty self tappers) & re-route / re-hose.
Replace splash guards ETc
Best of luck.
Dean

 

[stilosporting]

when you removed the map sensor how did it look? was it fairly clean or gunked up at all? glad you are are going further with diagnosing this. very similar to my previous symptoms but the never found the cause. just replaces EVERYTHING instead lol. seemed to do the trick

edit: just posted at the same time lol. did you not try cleaning it at all? did i read in another post you cleaned the throttle body? have you looked at this since?

 

[stilosporting]

after reading this post https://www.fiatforum.com/stilo/115855-p0235-turbo-boost-sensor-circuit-malfunction.html im affraid to say the common denominator (sp?) is the cars have/had a remap on them. maybe the car is actually doing what the sensor is saying and overboosting?

 

[DeanF]

when you removed the map sensor how did it look? was it fairly clean or gunked up at all? glad you are are going further with diagnosing this. very similar to my previous symptoms but the never found the cause. just replaces EVERYTHING instead lol. seemed to do the trick

edit: just posted at the same time lol. did you not try cleaning it at all? did i read in another post you cleaned the throttle body? have you looked at this since?

Hi Stilosporting,

I did try to clean it, but it made no difference, I did also clean the throttle body, That was really gunked up with hard exhaust type soot. The Egr valve really does chuck some Sh!te into the inlet manifold .
I still have the Egr blanked off, So all has stayed clean for the time being !!

I had read that about the Re-map, Im hoping that the sensors just become gunked up , over sensitive & tempremental due to more boost from the remap !!!
Dean

 

[stilosporting]

was it just soot or did it seem to be mixed with oil?

 

[DeanF]

was it just soot or did it seem to be mixed with oil?

Around the throttle body area it was soot, On the MP Sensor it was a sticky gunky Soot. Others i have seen have been exactly the same !!!
I spoke to Angel Tuning about the overboost after the remap & they said they have had very few issues with the map, Generally it is down to a sensor being over sensitive or duff & just being triggered by the extra loadings !!

Dean

 

[stilosporting]

i got the same answer from the same company. although it could be right, one of the sensors is going loopy due to a change in settings. it may mean that when we find said sensor/part it will have to be regularly replaced or uprated if possible.

 

[DeanF]

i got the same answer from the same company. although it could be right, one of the sensors is going loopy due to a change in settings. it may mean that when we find said sensor/part it will have to be regularly replaced or uprated if possible.

Hmm.

Hopefully it is just the sensors, I will keep updating as things happen !! Or don't !!

Dean