I have just replaced a split turbo hose on my 2011 Vauxhall insignia. However after clearing the fault on the ECU the engine is still in limp home mode and the car says "Service vehicle soon" on engine start.

I've checked the pipe seals and there are no leaks.

What could still be causing the limp home mode?

  • If the service car soon light is on, there must still be a code which is popping? Have you looked at it again to see what might be there? – Pᴀᴜʟsᴛᴇʀ2 Jul 24 '18 at 1:10
  • @Pᴀᴜʟsᴛᴇʀ2 Nope this is the annoying thing, scanned several times and nothing is coming up! The small engine light is not on, just showing a notification on startup. Limp mode is now permanently on too before it would drop into limp mode and then would gradually pickup again. – caveman_dick Jul 24 '18 at 9:09
  • For how long was the car going whit split turbo line? – Martin Jul 25 '18 at 10:51
  • @Myself About 2 weeks I would think. Well the service light was on for about 2 weeks, hose may have been split for longer – caveman_dick Jul 25 '18 at 15:33
  • Have you cleared the fault codes? Typically a car may remain in the error state until a diagnostic tool is used to clear the fault codes. – Steve Matthews Sep 21 '18 at 11:45

Assuming that the car was for prolonged time in service with an damaged turbo line I think of the following possible scenario:

Normally a diesel is running lean (more oxygen than fuel). Since the split turbo line allowed metered air to escape, the combustion went rich (less oxygen than needed), this way the exhaust gasses where rich on soot. The large amount of soot over prolonged time can cause multiple problems:

  • The EGR valve could be clogged. Uncertain: This should definitely throw a CEL with corresponding code.
  • In the long term the intake manifold and other engine parts could suffer from soot-buildup.
  • The engine oil is contaminated with an larger-than-normal amount of soot.
  • The heavy amount of soot in the particle filter provoked often a filter-cleaning cycle (Fuel gets injected on the exhaust stroke, to burn off the soot in the filter. Detriment is the contamination of the engine oil with fuel)

My thoughts about the most likely cause:

I assume that the "service-soon" signal is caused because the fuel proportion in the engine-oil is too high as there where too many cleaning cycles. The engine counts them, as each cleaning cycle dilutes the engine oil. Now the engine oil is diluted up to the point where it needs to be replaced. Fuel diluted oil has worse lubrication quality than non-diluted oil, therefor the ecu activates the limp-mode to (somewhat) limit the damage to the engine

Bottom line:

Book a service (oil-change) for the car as soon as possible. Ideally you do this at a place where they are able to do further diagnosis (no quick-lube booth, perhaps the dealership or a reputable garage) as further investigation could unearth other causes/problems and avoid further damages.

  • thanks for this. I doubt that the oil will need changing as the car had a full service at the dealer about a week before I changed the turbo hose (they confirmed my suspicion). In that time I will have only done about 10-15 miles at most. – caveman_dick Jul 26 '18 at 8:58
  • 2
    @caveman_dick Then the dealership is the right place to ask them why you need a service one week after a full service. You could also ask them to measure the remaining capacity of the particle filter. – Martin Jul 26 '18 at 9:52

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