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Limp mode and flashing glow plug light

jfellows10

Active Member
May 14, 2020
56
9
Hello,

I have a 2017 seat Leon fr 2.0TDI 184 and have started to have issues with the car going limp. It does not want to go through the gears and will hold the revs in lower gears and if I put my foot down on the accelerator too much will throw on the glow plug light flashing this then goes off if I turn the car on and off but will come back on eventually if I drive with a heavy foot. I have had the glow plugs and glow plug sensor changed however this has not fixed the issue. Anyone else had similar problem even after changing all the glow plugs?
 

jfellows10

Active Member
May 14, 2020
56
9
Have you checked for fault codes?
Last time it was put on the diagnostic machine it was saying glow plug cylinder 3 and then I think there was another fault code either to do with the turbo or 000665 - Boost Pressure Regulation. I am going to get it back on the machine tomorrow morning and will update with the new fault codes after changing the glow plugs and glow plug sensor today. It has felt limp for a while at times but was only showed the glow plug light in the last week or so and it seems to come on regular if I put my foot down now too much. Started car again earlier went out drove fine then on way back thought I would try see if it pulls fine under some speed and then light is back on again back to limp mode. Didn’t even get up to near red line revs
 

BillyCool

Active Member
Jan 16, 2020
704
275
Leicestershire, UK
Okay - thanks for that. A car can go into limp mode for so many reasons. It's designed to stop you damaging the engine but allows you to at least get to a safe place.

When I changed my glow plugs I also changed the glow plug relay in the engine bay fuse/relay box. No idea if that would help your situation though.

If you are/were getting any sort of turbo fault code, that would put it in limp mode, even if it's intermittent. I changed my boost sensor (easy to do) when mine raised a code.

On a previous Leon, I had a slight air leak on a vacuum hose for the turbo and it only had an issue at higher revs when it was under more stress and then went into limp mode. So, it could be a hose and/or sensor issue.

I'd be guessing at the moment until you get some fault codes. It could be a relatively easy fix (don't hold me to that).
 
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jfellows10

Active Member
May 14, 2020
56
9
Okay - thanks for that. A car can go into limp mode for so many reasons. It's designed to stop you damaging the engine but allows you to at least get to a safe place.

When I changed my glow plugs I also changed the glow plug relay in the engine bay fuse/relay box. No idea if that would help your situation though.

If you are/were getting any sort of turbo fault code, that would put it in limp mode, even if it's intermittent. I changed my boost sensor (easy to do) when mine raised a code.

On a previous Leon, I had a slight air leak on a vacuum hose for the turbo and it only had an issue at higher revs when it was under more stress and then went into limp mode. So, it could be a hose and/or sensor issue.

I'd be guessing at the moment until you get some fault codes. It could be a relatively easy fix (don't hold me to that).
Right so the glow plug fault code has now gone however this is what is left…
The dpf code is new this wasn’t on the fault code list when I checked the other week. Haven’t had a dpf light come on the car. So will probably try a dpf forced regen. Still think it’s not just down to that though
 

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BillyCool

Active Member
Jan 16, 2020
704
275
Leicestershire, UK
The DPF code relates to a sensor issue rather than a DPF fault, so I wouldn't try forcing a regen at the moment. That might just be a bit of a distraction.

Ref the turbo code - this can mean many things from a bad turbo or just a bad sensor (inc. the boost sensor). See below:

P0299: causes, symptoms and repairs​

The meaning of fault code P0299

P0299 is registered when the supercharger or turbo for car is generating a low or insufficient boost pressure, therefore reducing the engine’s power output. If it does not reach the required pressure level, the vehicle may go into “limp mode”, shutting down the non-essential devices of the car.
Possible causes

  • Low pressure in the lubrication system, causing oil starvation and increased wear.
  • Blockages in the passages of the charger unit, which can occur when carbon deposits form and build up inside the components. This is often a consequence of using the wrong kind of car lubricant or not servicing the boost unit on time. As a result of this, the bearings can be worn down, the turbine component may overheat, and you may see signs of damage at the shaft.
  • A sooty exhaust gas recirculation (EGR) valve can also result in a build-up of carbon deposits, obstructing the VNT mechanism.
  • A clogged air intake system, reducing the effectiveness of the turbocharger.
  • Vacuum actuator failure caused by leaks
  • A faulty injector control or boost pressure sensor
  • A defective wastegate or solenoid failure. The wastegate valve is supposed to remain closed until the correct boost pressure is reached, however, if the regulation solenoid fails, the valve will stay open, stopping the charger from generating the boost.
Symptoms of code P0299

  • A loss of engine power or slow acceleration
  • Activation of the check engine light
  • An unusual or high-pitched sound coming from the engine
  • Activation of the vehicle’s emergency operation mode
  • Black smoke coming from the exhaust
Recommended repairs

  • Check out the related diagnostic trouble codes (DTCs) to identify the possible causes of the error. You can do this by connecting an OBD2 scanner to the vehicle.
  • Examine the condition of the hoses, pipes and vacuum lines linked to the boost unit. You will need to tighten any loose clamps and replace damaged pipe components and seals to prevent or fix leaks.
  • Do a visual inspection of the turbo/supercharger itself to check for cracks, chips, or loose parts, etc.
  • Check whether the sensors are working properly using an appropriate testing tool such as a multimeter. These devices can be replaced at a reasonable price.
  • Make sure that the wastegate is able to move properly and that the boost control solenoid is working. You can test it manually with an air pump or vacuum tester.
  • You may also need to clean the EGR valve and flush out the lubrication system to get the parts to run smoothly again. If the valve is damaged beyond repair, you will need to install a new one.
Frequently Asked Questions (FAQ)

What does the P0299 code mean?​

It indicates that the turbocharger/supercharger is not generating enough pressure to boost the engine.

What causes it?​

Common causes include charger or solenoid failure, air leaks, low oil pressure, and clogging.

How can I clear this error?​

This DTC needs to be followed up with a comprehensive diagnosis in order to determine the exact location of the fault. Once it has been identified and fixed, the DTCs can be reset using the scan tool.

Can I still drive my car or is it too serious?​

Due to the effect of the underboost conditions on engine performance, it is better to refrain from driving the vehicle until its fixed. Additionally, if the turbine is broken, parts of the impeller could break off and damage the motor.

So - this does not answer your specific question but it's a place to start. Since you may have 2 faulty sensors that both sit on the top of the engine, have you been through flood water or had anyone working on the car recently? i.e glow plugs? I'd remove and re-attach the plugs in case they've been leant on, removed and/or damaged. If you change sensors you sometime needs to so an adaptation exercise to tell the car a new sensor is fitted. I have no idea if that applies to glow plugs.

Try and check the obvious first. Replacing glow plugs can be a real effort and other things may have bene nudged/bumped in the process.
 
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