Posted by Andrew Cunningham on June 30, 2010, 4:34 pm
Year of Manufacture *: 2006 Engine Size and Code *: 1600 hhda 90bhp ( Optional ) Scanner Used: autodiagnos ( Optional) Fault Codes: p0234 turbo overboost condition
Hi folks
Struggling with a focus 1600 tdci peugeot engine i believe. Came in the other day the red cog light on dash comes on and car looses power. Switch it off start it up again and car runs fine until light comes on again, usually when engine is under load. plugged it in and 2 codes in it one for EGR valve and one for over boost. Cleared them gave it a good long run and light came on, checked the codes and both came back so fitted new EGR valve and new boost pressure sensor. Gave it another run and light came on plugged it in and only turbo over boost code present. We checked for any air leaks with smoke pro and found a leaking pipe seal so fixed that, also checked the waste gate is working and it seems to be OK. Tried it again and fault is still there!! if anyone has any ideas they would be appreciated thanks Andy..
Re: ford focus 1.6 tdci red cog light on dash turbo overboost
Hi, if the fault code is saying "over boost", then, if it was me, I would go away and find out how the boost pressure is controlled on that vehicle and armed with that new found knowledge start working through the control system one section at a time. HTH
Regards Mark Modern cars, Its all wizardry and witchcraft
Re: ford focus 1.6 tdci red cog light on dash turbo overboost
After the EGR valve is replaced or after the PCM is replaced/reprogrammed, the EGR valve must be initialized by the PCM via IDS. The servo motor acts as a DC motor that sets the requested opening cross-section of the EGR valve.
Also it will be a safe bet, The PCM will require a Update for EGR valve software weakness.
Actuation is by means of the PCM using pulse width modulation. The exact position of the EGR valve is established via the position sensor. It is therefore a closed control loop.
Note: Each time the engine is stopped, a cleaning mode is activated by the PCM, whereby the EGR valve is moved from its fully open position to a completely closed position (by means of maximum activation of the DC motor).
However, the longer the engine is in operation, the greater the likelihood of residues forming on the valve seat of the EGR valve as a result of the exhaust gases flowing past it. These residues can cause the mechanical closing point of the EGR valve to shift. For this reason, the closing is re-adapted at regular intervals. Consequently, the position sensor also retains its precise measurement after a long period.
So basically the EGR DTC faults will return again once a few drive cycles are completed.
On a variable turbocharger, the boost pressure is regulated by adjusting the guide vanes. This means that optimum boost pressure can be set for any operating condition. The boost pressure actual value is measured via the MAP sensor. The set value depends on the When a control deviation occurs, the guide vanes of the variable-geometry turbocharger are adjusted via the boost pressure control solenoid valve.
Hope this helps a little , its not as simple has most people think it is.
Professional Diagnosis and Fixing modern cars requires lots of very expensive equipment , many hours of technical training , access / subscriptions to manufactures data and years of experience.
Garage general does not mean you can fix / diagnose every job that comes through your door.
Take the Automatic gearbox for example if a car turned up with a gearbox fault , 99.9% of garages ship it out to a auto gearbox specialist.
trying to Diagnose faults on modern vehicle systems is no different. Most jobs require a specialist to carryout a full evaluation of what's wrong with the car.
Just by reading your post , its sounds like you are just guessing at what is wrong with this car.
did you test & confirm 100% the EGR valve was faulty. Or was it honestly, lets fit this £200 part pray it fixes it.????
As regards to the MAP sensor , I would be 95% sure that there was nothing wrong with the original sensor. But if you knew how it worked and understood how to it test , then you would no for sure your self.
please do not take this the wrong way and get all upset.
Its just advise, seek out a local specialist that's close to you and form a good working relationship or become the specialist...
I have been saying it on this forum from the very start " if you do not understand how it works how can you fix it"
Re: ford focus 1.6 tdci red cog light on dash turbo overboost
hi, after we fitted the egr we took it to our local ford dealer who re-set the egr up and did a download on it as for the turbo it aint variable vane as i can see unless of coarse iam missing something. thanks for your advice i will look into it further today cheers andy...
Re: ford focus 1.6 tdci red cog light on dash turbo overboost
Hi Andy, I have had five vehicles with this problem in the last year or so and didn't check the boost pressure on any of them. Others may go this route but the cause has always been found quicker than the time it takes to set up pressure gauges etc. If the DTC is telling you that you have overboost then you probably have. As Darren has said, this should have perhaps been done at the point you replaced the MAP (or boost pressure sensor, whatever you want to call it). I will tell you that one the five had a leak at the vacuum pipe to the turbo control diaphragm, two had vacuum leaks on solenoid valves (not necessarily the turbo control valve), one of which the main dealer said needed a new turbo, and two of these had siezed turbo control, whether thats a wastegate or variable vane is not relevant. For further info the vehicles with siezed turbo control have usually just been purchased and driven harder than the previous pensioner that owned it! HTH's Bryan.