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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 20590
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an citroen c4 grand Picasso and the service light

Customer Question

hi, I have an citroen c4 grand Picasso and the service light keeps coming after approx 60 miles then goes into limp mode?
Submitted: 5 months ago.
Category: Car
Expert:  Shantal-Mod replied 5 months ago.
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I'm Shantal and I'm a moderator for this topic.
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Expert:  Matt replied 5 months ago.

Hello

if the service light keeps coming on then the ECU thinks its due an oil change but this shouldn't put the car into limp home

I'd suggest the next step is to plug a scan / diagnostic tool into the car and read off what fault code is stored

from your description its sounding like there's a lack of power so there's some basic checks to do

So 1st consider changing the fuel filter as if this partially blocked this too will reduce pressure.

If both of these are OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues and its best to have the boost pressure measured actually measured with a boost gauge to check that the turbo is healthy and that the sensor is reading correctly

If its a variable vane turbo (they’ll be an actuator on the turbo body - but not a wastegate) then check its vacuum pipework as above and check the connections to the diaphragm / solenoid valve

Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home

Also worth considering adding a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked

Also check all the high pressure hoses post turbo/s for any split hoses or cracked metal pipes, also check the ends of the intercooler as its not unheard of to pop the end caps off under high boost.

Customer: replied 5 months ago.
At the moment your answer covers so much ground it would cost a small fortune to do all these checks. Ttheir is no loss of power, just loss of auto gears, and when going down manualy will not go beond 3rd. If you stop and switch off and start again every thing is back to normal including auto gears.When i first put my question the mechanic said that for the 20 pounds he had the answer to my problem, it appears this not so, this looks more like a scam when you are fishing in the dark.

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