From a very fed up owner.

[pistons]

:mad: I am one 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 since bought a Ross-Tech 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.



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.
I measured the cylinder pressures in case there was a burnt valve creating some back pressure – no signs of that.
I replaced the force (MAP) sensor on the inlet manifold as this is the sensor reads the manifold pressure. – P0106 error still reocurred.
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.
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.
Note: Dismantled the old brake switch and found it to have been OK and probably not at fault.
I have taken the inlet manifold off and examined if for damage. All seems OK
I have cleaned out the throttle body. A bit dirty but cleaning it did not change anything.
I have used Ross-Tech to reset the throttle position sensor. Does not cure the fault.
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 areal 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 come
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. 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.


:aargh4: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.

[martin1810]

An occasional break in the wiring or a dirty connection, between the map sensor and the ecu could cause this problem. Air leaks in the inlet manifold can also cause it. Unfortunately both of these are very hard to trace.

[towcestervag]

ive had this before but it was four different issues
1 map sensor fault
2 engine ecu required reprogramme to a later software version
3 cam timing had slipped
i would check the cam timing first as ive had this several times
4 the valves get sticky and the cylinder head requires a rebuild

[pistons]

Thanks for all the hints. Tried to find a used throttle body but could not! In the end took throttle body off and opened it up by cutting through the large swaged band. Then used air line to blow out any debris from inside it. A puff of black dust came out - not a lot but significant from a sealed unit. Refited swaged band + long jubile type clip to remake the seal.
Did this several months ago and has been OK since then, touch wood.

PS. how do I find out the firmware version of the ECU? Can VCDS get it? What is latest fabia 1.4 16v DOHC firmware version? I might still need to update that.

[bw10030]

If sticky valves are an issue, use a good oil flush - had this on a Rover 1.4 'K' series engine.

Get some oil flush additive, add to the oil and run for 20 or 30 minutes on the drive (idle speed with the odd 'fast idle'). Then drain the oil, change the oil filter, put in new oil, then go for a good thrash to clear the cr*p out of the system.

On the Rover, the problem is a build up of carbon on the valve stems, which stop one (ore more) closing very slightly. This allows 'overpressure' to affect the manifold pressure sensor, which sends the system haywire by upseting the ECU.

Reccommended fix was a head rebuild (very expensive). The oil flush worked just as well and cost £50 max!

Good luck, it can't do any harm.

[vtsnick]

Sounds a pretty ingenious find! To cut open the TB and have success..!! One well noted in the battle against VAG slackness!

[chrisbower]

Had similar trouble with an old Volvo. Turned out the air mass detector had some crud on it - tiny bits of foam rubber from the air filter box - wires overheated and the EMU kicked it into LH.

[pistons]

Perhaps I should, at last, put this one to bed.
My repaired throttle body lasted a while but the fault soon came back. A new throttle body cured the problem.
Since I wanted to know why the old unit had failed at 60,000 miles I cut the old throttle body open to look for the cause of the failure. I found it. The wipers, which run over the screen printed resistor tracks inside the throttle body to sense the angular displacement, had cut right through the tracks over approx the first 10 degrees of movement. The ends of the wiper wires/fingers, which are shaped to press on the tracks at right angles, had worn (or were made that way) to have very square ends with very sharp edges. These sharp ends had cut right through the tracks near to the start of each track. This meant that the wipers lost contact and went open circuit.
Just why the diagnostics could not have spotted that and clearly reported that the track resistance in the throttle body was too high eludes me. Instead it meekly reported error code P0106 "manifold absolute pressure /barometric pressure circuit/ performance problem" - quite the wrong diagnostics.

In my professional life I was a software engineer and I am clearly not impressed with the VW skill at error handling.