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P1235: Positive boost pressure governor deviation

16K views 39 replies 8 participants last post by  tomfromtelford 
#1 ·
Had a few issues with my facelift 156 1.9 JTDm since it was parked up for the most part of 6 months. I have fixed the immobliser issue with a Inj. relay clean, a P1238 error with an EGR clean. Battery has been removed for a very long recharge.

The only issue to resolve is a P1235:
Failed Component Code: Positive boost pressure governor deviation
Fault Symptom: Positive governor deviation above limit
Warning Lamp Status: Warning Lamp Illuminated
Fault Test State: Test not complete for this Error.
Fault Code Storage State: Error Present at time of request
Event Count: 40 count
Environmental Condition One: Engine Speed: 3435.38 rpm
Environmental Condition Two: Fuel Quantity: 60.54 mm3/str
Environmental Condition Three: Accelerator Pedal: 71.76 %
Environmental Condition Four: Rail Pressure: 1521.54 Bar
Environmental Condition Five: Turbo Pressure: 1764.75 mBar
Environmental Condition Six: Engine Temperature: 91.63 °C

The car drives fine, but if you go for some heavy pedal you get the P1235 error. This then put the car into safety mode, and I have to reconnect AlfaDiag to clear this (only) error code. Now, I find it hard to believe the Turbo is dead. It has been idle, not thrashed. My other remedies were to do with cleaning something. Is there something to clean for a P1235 error ? I have read on the forum that it could be a split hose, but I have no idea where to look. Can somone please shed some light on this problem for me.
 
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#2 ·
afaik thats either a failed egr valve or stcuk turbo vanes..... i'm no expert on JTDs.... only read a few jtd threads
 
#4 ·
Thanks, but I've already done the EGR clean, that fixed up my constant P1238 error: Failed Component Code: Air control negative governor deviation

I should point out the 'motor control system failure' icon does not disappear, even after a restart. It requires AlfaDiag to clear it. I know this info may help narrow down the issue.
 
#5 ·
according to another list it claims that P1230 thro P1239 is related to Fuel Pump issues

P1230 Fuel Pump Low Speed Malfunction
P1231 Fuel Pump Secondary Circuit Low, High Speed
P1232 Fuel Pump Speed Primary Circuit Malfunction
P1233 Fuel Pump Driver Module Off Line
P1234 Fuel Pump Driver Module Off Line
P1235 Fuel Pump Control Out Of Range
P1236 Fuel Pump Control Out Of Range
P1237 Fuel Pump Secondary Circuit Malfunction
P1238 Fuel Pump Secondary Circuit Malfunction
P1239 Speed Fuel Pump Positive Feed Fault
 
#15 · (Edited)
remove the turbo & fit an recon'd unit

or remove the turbo & try sort it yourself.

others have done so.
 
#17 ·
I had a P1238 problem when I blanked off my EGR, but I also had a loose connection on the EGR solenoid.
It seems like a poor design, the connection "hangs" off the solenoid. Had a problem with clean connection between connector and solenoid. I would suggest checking the connection and make sure the Yellow "lock" is in place.
Contrary to the Boch fault list the P123X range seems to refer to EGR problems. Took a bit off trail & error as no-one on this forum could help me.
 
#20 ·
#25 ·
Where does fuel pump come into it ?

As I said earlier I was gettin a P1238 error all the time. I removed the EGR, then cleaned out the soot. I did not remove the solenoid.

I only get the P1235 error when driving and putting my foot down. The MCSF error can only be cleared by AlfaDiag. It does not turn off that error message after a restart.
 
#29 ·
If you still think it is the EGR then could I simply test it by disconnecting the electrical connector (I realise that in itself will create a new error in AlfaDiag). Next I take it for a spin with some heavy foot work. If I don't get a P1235 then it is an EGR problem ? If I still get the P1235 then the EGR is ruled out. What do you think ?
 
#31 ·
I don't think its EGR related, its sticking vanes. Foot down = lots of exhaust gasses = lots of force on the turbine to create more boost. Vanes should back off as boost is approaching the limit, they don't, there's your overboost error code, car goes into safe mode to protect itselt.

I don't know if anyone has used this before but it sounds like it could help you clean the turbo without dissasembly:

Innotec Supplies Ltd. - Turbo Clean Set
 
#33 ·
I noticed a perforated pipe....
As a quick fix I put some insulation tape around it until I can book it into a garage. I just did a 200 mile round trip and I only the got the P1235 error once, so it is an improvement.

I have done more testing and noticed I don't have much performance below 2500rpm, most noticeable in higher gears.

So that, combined with my P1235 error, is pointing to what as the culprit ? Is it still the turbo vanes or now likely to be the VNT solenoid perhaps ?
 
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