Turbo short circuit to positive..??...FIXED.....

[GingerMagic]

Hi, I was wondering if anyone could help me.

I have this fault code pop up every time I drive with gusto, which I initially thought was an overboost issue. I've treated the car to a new MAP sensor and Turbo EV, as well as new silicone vac pipes - I even squirted WD40 into the vanes to try to sort the MIL.

I checked on PP2K and it turns out its a 'short circuit to positive' fault, P0235 which happened at 2891 RPM and the recorded boost pressure was 2518 mbars.... the fault doesn't affect performance ( other than occasionally lacking power on the upchange ) and it will clear itself after a day or so.

Any ideas?

Edit;

Right, I had a few hours on the car today....

Changed the fuel filter.

Removed strut brace to get the engine cover off. I started to remove the EGR, dropped my 10mm spanner down the back of the engine.
Removed the undertray, retrieved the 10mm spanner then I removed the EGR, put some cleaner down it then dropped the screws for the EGR.
Couldn't find the screws so removed Finchies EGR blank from the donor car, put this on my car with a new paper gasket. Dropped a bolt for the strut brace down the back of the engine - no idea where that went....
Removed the Nicopipe as there was a leak, cleaned the edges and put a paper gasket on that too.
Removed a strut top bolt ( albeit a shorter one ) from donor car to refit the strut brace

Took the car for a test drive and the EML light came on straight away, lost my brakes

Came back, removed the vacuum pipe from under the engine cover where it was kinked, swapped the turbo solenoid and went for a drive - EML light back on but brakes working fine.

So I still have the 'short circuit to positive' fault, but the turbo is cleaner.

Went indoors, emptied the dishwasher, had a shower, put some washing on then the wife came home and whinged about me putting a wash load on with the labels still on a pair of jeans ( the jeans that she put in the basket without removing said label - my fault of course )

Not sure what to try next regarding my boost issue??

[Uberderv]

Would of thought it be the wiring to your Electro valve is on the fritz. Besides that, your description of work done was reet proper amusing

[GingerMagic]

Hmmm, there's a thought.

I thought I may have a dodgy replacement MAP sensor which was giving duff information, but it reads 1bar ( approx ) on tickover so I think its alright.

How would a ham-fisted buffoon like me tackle the job of finding a possible wiring fault with the turbo EV, do I just strip back the sleeve and take a peek?

[madmadmax]

multimeter and a pin

[Doggy]

This here's the circuit for the turbo EV



1320 is the engine ecu, 1233 the turbo EV, BM34 the engine fusebox.

I suggest checking / re-seating the ecu connectors and making sure you have a good earth on the two ground connections:
- wire MC21D on pin H4 of the 34-way black connector
- wire MC21c on pin H1 of the 34-way grey connector

I've seen quite few instances of 'short cct to +ve' error codes that don't case any issues, like the common pre/post heating error message.

I suspect you really do have a transient overboost problem. I beleive the error occurs at 1500 mbar above atmospheric pressure, or around 2500 mbar absolute.
The '200' map tries to control at 1400 mbar, (the '180' at 1200 and std at 1000, I think)
I realise you've done all the right things to eliminate an overboost problem - if it was my car, I'd try a different map at least temporarly to increase the margin between actual maximum boost and the overboost error limit.

I guess you could also consider swapping the turbo itself from your old car.

Mine does something very similar once in a while if I give it a blast before it's fully warm - the EML will come on, no effect on performance and it goes out a few trips later. I haven't bothered to check it with PP2k, but I will have a look over the weekend as it should have at least am intermittent fault logged. I'll let you know.

[Doggy]

Does this look familiar?



Read these from mine today - it hasn't generated an EML in the last couple of months and it's running pretty much spot-on.

I cleared the faults and they didn't come back during the following measurements.

These are my turbo pressures etc. at tickover, engine fairly cold.



at fast idle......



and at 2.5k revs.....



Hope that's some help?

[GingerMagic]

multimeter and a pin

Would the current be full time or only when the engine is revved enough to power the EV?

I have a multimeter but its still in the wrapping....

[jonsowman]

The EVs are controlled by PWM (pulse width modulation). The "Turbo OCR" value in PP is what the PWM value should be.

The multimeter might tell you something but it might be misleading/wrong, and there's no way to know. You need an oscilloscope really...

P.S. If you do try the multimeter, use it on voltage mode (not current mode), or you'll short circuit the driving circuit for the EV and that will make things sad.

[GingerMagic]

Oh, so I guess the Turbo OCR % should go down when you rev the engine..?

I'll check on PP2000 tonight and see what happens to the OCR.

The connector to the EV looked okay at first glance - tracing the wiring is another job to do in the daylight

[Doggy]

As Jon says, it will be misleading at best.

The most effective method would be to observe the result i.e. if you could watch the movement at the turbo to see if it changes along with the OCR%.
(Unfortunately, I've never even seen the turbo, much less whether it's possible to see the vacuum activated bits do their thang).

Just thinking out loud - I wonder if you could temporarily connect the turbo EV to the swirl flap diaphragm and maybe see it change position with the changing OCR% ?

[GingerMagic]

Good idea, I'll do that to test the EV.

My swirl is fine, only the ball keeps popping off, so its held together with an elastic band.......

Come to think of it, could I plumb the swirl feed to the turbo EV to see if it works at 2100RPM..??

[Doggy]

Come to think of it, could I plumb the swirl feed to the turbo EV to see if it works at 2100RPM..??

Be careful - that might give you....
no boost.....
no boost.....
Oh fcuk!

[GingerMagic]

Ha ha, thats kind of what I have now anyway........

[jonsowman]

Oh, so I guess the Turbo OCR % should go down when you rev the engine..?

Yep, I seem to recall around 60% at idle, dropping to around 10% at max boost.

By "max boost" I mean when under drive - revving the engine in neutral didn't have much of an effect because the ECU didn't want to apply boost with no load.

[GingerMagic]

I've just popped out to work on the car for 5 mins - its Mother's day so I didn't want to rock the boat....

When I plumb the vac pipe from the turbo EV to the swirl flap, the ball/socket moves back ever so slowly and doesn't move forward much when revved albeit when stationary. This happened for all 3 EV's I have ( 1 new 2 old ) so I think the EVs are okay, and on a quick blast around the block the car behaved as it has been - slow to rev up to 4Krevs and peeks at 2K revs on the upchange, unless I throttle off a bit and then it will slowly rev to 4K....

Looks like either a wiring issue or my turbo's diaphragm is goosed.

Ho hum, I'll check the wiring when its daylight sometime next week.