Fabia 1.4 16v epc persistent problems

[pistons]

I am one very fed up Skoda owner (Fabia ’03, 1.4l, 16v).

The EPC warning light has been triggering fairly regularly for the past year+. This begun whilst the car was still under warrentee but the Skoda garage said that no fault code had been written to the logs so they could not help. I find this strange, since having now bought a Ross-Tech VCDS and a Gendan "Engine Check Pro" reader, a P0106 code is always written to the log after the EPC light has triggered.

The fault seems to occur most often whilst negotiating small local roundabouts, usually just as pulling away from them. It has also occured whilst pulling out to overtake!!! - I rarely do that now in this car - I don't trust it!!

The EPC light has come on many times but twice it has come on and the EMU immediately switched into the dreaded limp home (LH) mode. Oddly, the LH mode could be cleared if the wiring plug on the throttle body was disconnected and reconnected (with the engine off). At first I thought this may be due to a poor contact etc but it all checked out OK with a DVM.

Pulling the plug is not the ideal quick fix but this was the only way I could get out of LH mode and get home and then attempt a proper fix.

I also started examining simply everything and replacing the various parts and sensors that may be causing the P0106 code.

1. I found a crack in the tube between the throttle body and the brake servo. This would effect the manifold pressure so I replaced the tube – better brakes but the P0106 error continued to reoccur.

2. I measured the cylinder pressures in case there was a burnt valve creating some back pressure – no signs of that.

3. I replaced the force (MAP) sensor on the inlet manifold as this is the sensor reads the manifold pressure. – P0106 error still reocurred.

4. I measured the manifold pressure, using the EngineCheckPro software, with the engine idling, accelerating and decelerating etc. before and after the force sensor was replaced. The range of readings obtained was the same before and after. All readings seemed reasonable and credible. The P0106 fault code continued to reoccur.

5. I replaced the brake switch above the brake pedal as suggested on the Skoda Fabia forums. Reports suggest that this part often fails and, since it is part of the EPC logic, could cause this problem – despite replacing it the P0106 error still reoccurs.

6. Note: Dismantled the old brake switch and found it to have been OK and probably not at fault.

7. I have taken the inlet manifold off and examined if for damage. All seems OK

8. I have cleaned out the throttle body. A bit dirty but cleaning it did not change anything.

9. I have used Ross-Tech VCDS to reset the throttle position sensor. Does not cure the fault.

10. I have checked the fuel pressure on the delivery rail – all OK.

During the many many months of bother the only code that ever gets repeatedly logged is P0106 signifying a “Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem”. There was a single occurrence of a P0170 and a P0106 occurring together but as a cell in the battery failed at that time I don’t know if this was a real problem or an simply another fault which I then cleared by replacing the battery. The P0170 code has not recurred since the battery was replaced..

On perhaps a third of the occasions when the EPC light shows the TSR light mometarily comes on as well but no extra codes are recorded, only P0106. From what I have read, the TSR light comes on if the TSR unit fails and this will cause that light to stay on and log a fault code. It is also said to show but clear itself if the battery voltage falls too low. This then clears if the engine is restarted.

Two pieces in this control circuit which I have not yet replaced are the throttle body and the accelerator pedal position sensors. Having already spent about £300 on parts (to no effect) I am reluctant to spend a further £160+ to replace the throttle body without some hope that this may be needed. Each of these parts seem to have fault codes of their own. Since I have not yet seen faults in the range P0120 et seq, P0221 et seq or P1171/1172 I am reluctant to replace these actuators/sensors.

From what I read on the forums this type of EPC problem is not uncommon, with many owners and garages struggling to solve this. Why cannot the EMU give a better hint about what is wrong. Despite the fault readings that I see all I am left with is questions and no solution.

Is failure of the throttle body likely? I am puzzled as to why unplugging the wiring to the throttle body can snap the car out of the LH mode. I have used a DVM to look for a poor contact etc. but cannot see a fault. In any event I have never seen any of the error codes which I would expect to see from a malfunction in the “drive by wire” parts between the throttle pedal and the throttle body. Surely, if the throttle body etc was defective, wouldn’t this produce some codes other than P0106.

:orb_mad: PS. The habit of switching to the Limp Home Mode instantly without warning has proved to be extremely dangerous. This problem first occurred, without warning, whilst overtaking, but fortunately I was not on a motorway! Surely there must be some other way to warn the driver of the fault and to allow sufficient time for the car to be brought to a safe halt in a safe place. The instant loss of power and the rapid deceleration that follows could easily leave one stranded in the fast lane of a motorway with nowhere to go apart from the mortuary. At the moment I dare not go on motorways with this car. I consider this to be a very serious safety issue.

[MoggyTech]

I would suspect a sticking throttle body stepper motor. The clue is in unplugging the throttle body wiring clears the limp home mode. If you can adapt the new one yourself, try one from a scrappy.

Modern cars eh, too clever for their own good.

Think I would rather have it go into limp mode on a motorway though, rather than some little B road while over taking.

[pistons]

Thjanks, I had not thought of that - worth a try.

[jakeelee]

Hello,

Did you ever find out what the problem was?

I now have the same problem on my Fabia-03 1.4 16v.

Thanks in advance

[Tom_S]

Apologies for bumping this, however I am experiencing EXACTLY the same problem that pistons described.  Eerily similar in fact, right down to the fact that the problem occurs frequently on exiting roundabouts.

 

I will PM pistons and Jakeelee directly but suspect they are long gone (last visited 5 years ago).

 

Has anyone else has the same issue? The car is reaching the end of its life so I don't want to spend much money on it.

[Breezy_Pete]

Can't think how to search for it just now, but there was a thread on here a while back (3 years ago?) with a mysterious, persistent MAP-related fault code (I think) that turned out to be the airbox  thermostat having failed in the 'hot air only' position (which is their natural failure mode, unfortunately).  The fault code gave no indication that it was the temperature sensor part of the MAP which was giving unexpected readings.

@Tom_S, maybe try running without the airbox on and see if the fault goes away for a journey that would typically provoke it?  Or if you have VCDS or something else to give live data, look at the intake air temperature and see if it goes high and stays high.

[sepulchrave]

You can jam the wax thermostat in backwards so the airbox is permanently stuck on cold setting, this is what I ended up doing and experienced no issues in the winter because it doesn't get cold enough here.

[Tom_S]

@Wino and @sepulchrave, thanks for your help and suggestions. The local garage had mentioned looking at the EGR system as a first step so that all fits. I'll try monitoring the intake air temperature and see if it goes high as you suggest, if I can do this using my OBD reader and the Torque app.

[Tom_S]

Just to update. The garage have cleaned the throttle and EGR valve and the car is running much better. The engine used to be very rough whilst idling and is now noticeably smoother. I've done about 300 miles and the frequent EPC faults (p0106) have vanished, however my son reported that the car threw a fault and cut out on him on a recent long journey so there may be some other issue at play as well. I'll try and find my OBD reader and have it to hand in the car for when it next happens. Thanks again for everyone's help.

[fabdavrav]

On ‎03‎/‎07‎/‎2018 at 17:35, sepulchrave said:

You can jam the wax thermostat in backwards so the airbox is permanently stuck on cold setting, this is what I ended up doing and experienced no issues in the winter because it doesn't get cold enough here.

 

Or get rid of the OEM air box & build your own (using Green Cotton components) fully sealed CAI....with way bigger diameter pipework & bigger washable filter...like I did...& No problems...

 

 

Mind you the person who bought it off me wanted it reverted back to OEM...so I wonder if they now have this problem??.