Engine overboost condition (P0234)
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Thread: Engine overboost condition (P0234)

  1. #1
    Hi all,
    I have a late '05 9-3 1.9 TiD 150 bhp (105k miles) vector sport which I purchased in the UK about two months ago. Since then I have some of the "usual" 9-3 problems (broken front coil spring, egr valve, serpentine belt tensioners), but last week a new one appeared...

    I was accelerating (pretty hard) in fourth gear, the engine management light came on and the car went into limp home mode...
    I got home and disconnected the battery for ten minutes hoping the light would go out but no good. Took the car out for a drive and it seemed fine full power etc but I didnt push it too hard. After that I drove the car as normal and ordered an OBD II code reader (€30 on Ebay).

    The code reader showed up P0234 (Engine Overboost Condition), which I reset and drove as normal. It was about a week before I took the car for a proper run out after that and again while overtaking hard in 4th gear the light came on and limp home mode ensued. I stopped and turmed off the ignition and that again solved the low power problem and once I got home I reset using OBD reader again it showed P0234.

    I looked around on forums to see if it is a common problem but could find no such problem with Saabs. On forums for other marques they suggest that it may be caused by a blocked pipe or something like that so I had a look under the bonnet and could find nothing out of place (although I'm no expert!)

    Anyway I took the car out this evening tosee if I could pinpoint the problem and it only seems to happen under acceleration in 4th or 5th just above 3500rpm. First, second, third are no problem... The limp home mode disappears if the ignition is turned off (even while coasting) and power is fine until hard acceleration in fourth abd.

    So... Has anyone any idea what might be causing this, or had a similiar problem, and more to the point how do I fix it? Really appreciate any help!

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  3. #2
    Saab Fan
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    Try this link:

    http://www.justanswer.com/questions/...fix-p0234-code

    and

    http://www.saabcentral.com/forums/sh...d.php?t=146960

    I've had a look around and it is an overboost problem of some kind. I have just had a new intercooler fitted due to over boost but I don't know what code it threw out.

    Dan.

  4. #3
    Full throttle mark e's Avatar
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    From what I can see in WIS, it's an error indicating that the boost pressure is too low i.e. less than the ECU is requesting. The fault condition only occurs if the revs are above 2750 and the boost pressure is too low for 4 secs or more. This may be caused by:

    - an air leak in the system
    - faulty turbo
    - faulty solenoid valve
    - faulty sensor reading
    - blocked exhaust

  5. #4
    that's a nasty code to get it means you have damaged the turbo or split a pipe feeding it P0234 = mechanical failure in the turbo caused by enthusiastic over revving in a certain gear,

    basically you killed the turbo.

  6. #5
    that's a nasty code to get it means you have damaged the turbo or split a pipe feeding it P0234 = mechanical failure in the turbo caused by enthusiastic over revving in a certain gear,

    basically you killed the turbo.[/b]
    What?? I'm sorry mate but you can't say that he has damaged his turbo in that way. If the guy doesn't know that much about cars he's going to take what you say seriously without maybe getting it checked. I'm not saying it's not the turbo but there are other things that can cause this code, split pipe, intercooler, turbo wastegate, boost control valve or even the ecu/wiring.
    If the turbo was the problem wouldn't he have problems in all gears across the rev range??

  7. #6
    sorry mate but I don't hold back on the facts I was quoting WIS on this fault code but also note I have also pointed out it could be split pipe so the investigation is around the turbo area.

  8. #7
    P0234 5B

    Important
    Read the introductory instructions below and then click on the tab to start the fault diagnosis procedure.

    Boost Pressure To Low Mechanical Fault

    Fault symptom
    Fault indicator lamp (for further information see WIS Fault diagnosis, general)

    Performance loss.

    Cruise control not working.

    No A/C function.

    On-board diagnosis
    Type of diagnosis:
    Continuous


    Enable criteria:
    Engine running. Engine speed higher than 2750 rpm

    Fault criteria:
    Current boost pressure falls below requested boost pressure for more than 4 s.

    System reaction to a fault:
    Limp Home, engine torque limitation. Output to the A/C relay is switched off. EGR turned off in case of fault.

    Diagnostic help
    Diagnosis regards:
    •Diagnostics compares requested and current boost pressure. A DTC is generated if the current boost pressure is lower than the requested boost pressure.
    9-3 (9440) 5 20051
    0. GeneralBulletins - SI/MI - (103-2469) C...
    •The diagnostic trouble code indicates a mechanical fault in the turbo, air leakage between turbo and intake, in the vacuum system, broken solenoid valve or misleading charge air pressure sensor. •The DTC can also be generated if the exhaust system is clogged, coked up catalytic converter for example. •Mechanical fault in the turbo unit or air leak in the system.


    9-3 (9440) 5 20052

  9. #8
    0. General-
    *
    P0234 5A

    Important
    Read the introductory instructions below and then click on the tab to start the fault diagnosis procedure.

    Boost Pressure To High. Mechanical Fault

    Fault symptom
    Fault indicator lamp (for further information see WIS Fault diagnosis, general)

    Performance loss.

    Cruise control not working.

    No A/C function.

    On-board diagnosis
    Type of diagnosis:
    Continuous


    Enable criteria:
    Engine running. Engine speed higher than 2750 rpm

    Fault criteria:
    Current boost pressure exceeds requested boost pressure for more than 4 s.

    System reaction to a fault:
    Limp Home, engine torque limitation. Output to the A/C relay is switched off. EGR turned off in case of fault.

    Diagnostic help
    Diagnosis regards:
    Diagnostics compares requested and current boost pressure. A DTC is generated if the current boost pressure is higher than the requested boost pressure.
    9-3 (9440) 5 20051
    0. General-
    The diagnostic trouble code indicates a mechanical fault in the turbo, air leakage between turbo and intake, in the vacuum system, broken solenoid valve or misleading charge air pressure sensor. Air leaks between the turbocharger and the inlet can quickly cause damage to the turbocharger due to overrunning. Mechanical fault in the turbo unit or air leak in the system.

    9-3 (9440) 5 20052


    hopefully this explains it better

  10. #9
    Hi, havent had the chance to do anything with the car since, (Family funeral), so have been driving around cautiously trying not to push the engine too hard!

    I rang my dealer this morn and told him the story, and he immediately guessed the EGR valve to be at fault. I told him I had cleaned this recently and he said it was probably the electrical side of the the EGR rather than the mechanical side that was causing the problem. I'm a bit sceptical of this as havnt seen any overboost problems linked to an egr valve on any forum! Is this a possibility or is he just trying to sound like he knows what he's doing??

    I have seen on some VAG forums that the problem may be caused by a fautly Mass AirFlow meter (MAF) and that its safe to disconnect these to test if the problem goes away. Can this be done on the Saab also?

    I'm currently booked in to the dealership later in the week for a diagnostics check that will cost €90. I asked the service guy if this is going to pinpoint the problem as I had already knew the fault code was P0234 engine overboost condition. He said their computer will give a more specific code/diagnosis of the problem. I'm just worried that he'll charge me the €90 to tell me what I already know then try to con as much money out of me as possible for labour trying to find the problem!

    Will their diagnostics be better than the OBD II for locating the problem or will they have to go through the same process of troubleshooting to find the problem??

    Anyway, I appreciate responses so far, I dont think (fingers crossed) that its a turbo problem as the power is fine up to about 80 mph when limp home kicks in. Is it a difficult job to replace the intake hoses in case they're leaking? Anyone know where theres a schematic of the engine showing where they all are??

    Thanks in advance!

  11. #10
    Full throttle mark e's Avatar
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    Anyway, I appreciate responses so far, I dont think (fingers crossed) that its a turbo problem as the power is fine up to about 80 mph when limp home kicks in.[/b]
    If in top gear then it follows that you wouldn't get the fault earlier as you wouldn't meet the minimum rev requirement (2750) until around that speed.

    I doubt it would be an EGR problem.

    The Saab diagnostic stores more than just the fault code- it typically records a snapshot of the other parameters when the fault occurred, which aids diagnosis.

  12. #11
    okay,
    so I brought the car to the dealership today for the diagnostics check and long story short, the wastegate actuator has been identified as the problem.
    They tell me this will require replacement of the entire turbo unit at a cost of about €850 for the turbo and €400 labour, despite the fact that the turbo is fine and its simply the faulty wastegate thats causing the problem.

    Can the wastegate be changed without changing the turbo or are they as inseperable as siamese twins?

    The service guy also advised me to make a claim to directly to Saab UK to see if they would make a contribution towards the cost. However as it is a late 05 (06 model) with 105,000 miles he reckons theres not a great chance of success. Is it worth making the claim anyway and how would I go about it?

    He also said that this is the third UK import that they have diagnosed with this problem in the past year and says its due to the salt on the British roads clogging up the mechanism so it must be a pretty common problem for cars in the UK?

  13. #12
    okay,
    so I brought the car to the dealership today for the diagnostics check and long story short, the wastegate actuator has been identified as the problem.
    They tell me this will require replacement of the entire turbo unit at a cost of about €850 for the turbo and €400 labour, despite the fact that the turbo is fine and its simply the faulty wastegate thats causing the problem.

    Can the wastegate be changed without changing the turbo or are they as inseperable as siamese twins?[/b]
    dealers, heard it all before Z20LET engine (older astra gsi/vxt220) and occasionally the recirc valve splits on the turbo, vauxhall dealer say its a whole new turbo. Enter the new Vauxhall astra VXR (z20leh engine) and it had a issue with the recirc valve splitting in the turbo frequently. Suddenly, vauxhall release a warranty "recirc replacement" kit! £100. Same kit (genuine KKK) was available all the time from AET turbos for £30 delivered

    Anyway, i digress! I am not familar with the specific turbo but, i would be 90% sure the actuator cap and rod can be changed - the only issue wrt to this part is if there is damage to the penny washer/arm on the turbo body, but from what you say it doesnt sound like that. I had a uprated actuator on my VXT220, about £100+fitting (1hr)

    edit: just to add your warning is due to the ECU controlling the solenoid, which should move the actuator, closing the penny washer, causing the engine gasses to spin the turbo, increasing boost inlet side. As your actuaor is knackered, its not closing the penny washer hence low boost and ECU raising error (sorry if i am teaching you to suck eggs!)

  14. #13
    Full throttle mark e's Avatar
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    Rather than shell out for a whole new turbo, I would suggest sending your one off for a refurb. If it is indeed only the capsule then it will be much cheaper than a whole new turbo.

  15. #14
    The dealer has now told me that he has an engine in stock that he removed from another 1.9tid 150 from which he could take the necessary parts. The water pump seized in that engine and the timing belt came off so the entire engine was replaced.

    He says he can do the entire job labour parts and labour included for €600.

    Am I right in thinking that even if I did get the turbo refurbed as suggested by Mark E, that the labour costs would be pretty significant? The dealer says its about 4 hours labour to replace the turbo?

    At the moment it looks like I'm gonna go with what the dealer is suggesting...

  16. #15
    okay so that was 6 months ago, and i havnt done anything about it (well I bought a turbo from a breakers but it was seized so I sent it back). I know how to trigger the fault code when I want to (just to check its still there) but other than that it doesnt cause me any problems.

    The problem is that the wastegate actuator is not letting the boost out causing increased boost pressure in the turbo, which the ECU regards as a fault and sends the engine into limp-home mode until the ignition is reset (turned off and back on).

    My question is that if the modified the ECU with something like,

    http://www.elkparts.com/product_info...oducts_id=3823

    would that increase the allowable boost pressure in the turbo and therefore stop this fault code from appearing?

    I know its unlikely but maybe its worth a shot, i.e. I'd have to spend €600 on replacing the turbo, whereas an ECU upgrade might work and give me improved performance/fuel economy for the same price.

    BTW, does anyone know
    1) What boost the engine runs at? (1.9 TiD 150 bhp),
    2) At what boost the overboost condition would appear?
    3) What boost would the engine run at if the ECU was modified?

    Anyone think this is a stupid idea and I'm an idiot for thinking it might work??

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