P0238 Diagnosis - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 09-05-11 Thread Starter
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P0238 Diagnosis

Hi Guys,
I have been getting this fault code, only seems to occur when in higher gears, 5th & 6th and whilst accelerating. Motor Control Failure comes on and car goes into limp home mode.

I initially thought it might have been VGT solenoid not fully actuating, however I did check this using fiatecu software. It seems to move along it's travel no problem. However after initiating this test a couple of times if then fails to move.

I am thinking that perhaps the vacuum resivour runs out and the engine needs to be started to re-generate the negative pressure. Either that or I have soem leaking vacuum pipes.

Has anyone else checked their VGT actuator in this way and what did they observe?


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I'm pulling my hair out with exactly this problem on my JTDm 20V 156. The vacuum does run out (it will run out if you let the car stand for a few minutes). Probably enough to run one test cycle of the VGT solenoid on FiatECUScan.

My car shows a progressively increasing gap between desired boost and actual boost as you approach 3000 rpm or so, such that eventually the engine light comes on and I go into limp home mode. A lot of people on here talk about leaking vacuum pipes, but this makes no sense to me - if your vac pipes are leaking (ie closer to atmospheric) then the turbo is in 'minimum boost' mode - the car'll just be sluggish below 2500rpm and then pick up suddenly. Wouldn't give you an overpressure. In fact this is exactly what happens when I disconnect the vac pipe altogether from the VGT solenoid (the ultimate leaky vac pipe) - nothing below 2500 then normal performance in the higher rev range. I concluded my turbo vanes weren't stuck.

The MAP sensor seems to be giving sensible readings (do they fail by reading high?) so I'm a bit stumped really - I'd love to know what your fault tuned out to be!

Good luck with it
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I also had the same symptons and error code from my 156 1.9 M-jet, cleaning the MAP sensor as advised in another thread seems to have cured it. Hope that helps,


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(Post Link) post #4 of 6 Old 01-06-11 Thread Starter
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Hi Fletch,
I still have not resolved this issue, although it hasn't occured for a while either.
I havn't discounted that it could be sticking Vein mechanisim, a sticking mechanisim could cause the viens to move much more slowly than they should.

I also plan to replace the vac pipe as it is a cheap thing to do, an a small split of hole could cause the VGT actuator not to engage the geometry in time to alter the boost pressure before a fault is recognised by the ECU.

To summarise, dirty/obstructed VGT mech or slightly leaking vac pipe of even faulty vacuum solenoid could cause the system to respond slowly and the boost pressure to reach a level that the ECU determines is unhealthy.

I belive the VGT solenoid valve has a small foam air filter, would also be advisable to check all electrical connections. on the following MAF, VGT solenoid.

I have also heard MAP and possibly exhaust recirculation valve can cause issues.


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I have resolved this issue and it was the turbo vanes.

I got a new map and stuck it on - didn't sort it so i sent it back and got another from another parts place, so not the map - returned the second one too!

Checked all hoses, not the hoses.

Checked VGT and replaced that, didn't resolve it.

Cleaned the turbo out with turbo clean - issue resolved - HOWEVER, I saved up and had the thing reconditioned, some bearings were also thrown in as a result of some play in them - the issue has not occurred since.

It may not be the same issue for you guys but I thought I would share my experience.

Good luck guys
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I've got the same problem here..
Garage checked the hoses - not hoses..
Im going to get the turbo clean stuff and was thinking to get something to clean map sensor, but dunno what solution is the best? Do you use wd to clean sensors?? My egr valve have been replaced recently, some people were talking that it might get stuck open - maybe any1 know how to check that without removing it? Or as it is new one that shouldn't happen? I want my power back
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