Hi all.

I am in desperate need of help! I have a 2013 Superb, 170bhp 4x4. It has covered 105 faultless miles, but the coils light has started to flash when driving, putting it into limp mode. Switch the engine off, the fault goes away but will come back at any time, 10 yards to 10 miles.

Oddly, it seems to correlate with slowing & turning left! The car has been regularly serviced by a specialist Skoda garage.

The following work has been done by the garage, who are now stumped, & are suggesting the purchase of a donor car to swap parts, as the cost of investigation is rapidly mounting, & will soon render the car worthless!

 

Any help/previous experience would be greatly appreciated.

 

Investigate EML light & glow plug light still present . Vehicle in limp mode.

Carried out diagnostics – Code for G31 boost pressure sensor A high input.

Carried out test plan – replaced sensor.

Fault returned after 8 mile road test.

Carried out ECM reset & visually checked wiring to ECU using VAG breakout box. All ok, coming back with no breaks or shorts.

Removed ECU & sent away for investigation.

ECU returned with no faults present at time of testing.

Further investigation to continuing intermittent EML (coil light flashing).

Checked all vacuum hoses, connections & routes all good.

Carried out guided fault finding & test plans on N75 charge pressure solenoid – all good.

G31 pressure sensor recommends replacement despite new part fitted.

G581 position sender for turbo – All good.

All related wiring to & from ECU checked for continuity, short to positive & negative – all good.

Carried out Oscilloscope tests on same components – found when fault active, signal from ECM to N75 doesn’t invert when engine is started. Further investigation required to see is being inverted.

As fault is intermittent, & disappears as soon as ignition is turned off, difficult to diagnose as fault maybe caused by another component that shares live/earth in wiring system that is spiking the sensor.

Possibly needs donor to substitute parts.

 

Regards. Mike.

 

It would be good to post the exact list of fault codes for starters.

 

If your mechanic has diagnostic equipment capable of logging data while driving, it would be useful to log MAP, G581 position data and N75 duty cycle, especially if you can capture this when limp mode is triggered. VCDS is capable of doing this, I'm not sure about other tools.

 

Has the actuator on the turbo been checked? Ditto guide vanes on the turbine? Sticking guide vanes are notorious for causing limp mode, especially on gently driven cars.

Hi, appreciate the speedy response.

There was 1 OBD error code, can't remember it off my head, but will be home Saturday so will post the code then.

Not sure re the capabilities of the diagnostic kit, will ask the garage. Ditto the actuator & guide vanes.

Mine did this too and it turned out to be the EGR (exhaust gas recirculation) valve - not a cheap one to replace unfortunately. Started out with flashing coil and nothing showing on OBD2 code reader but swiftly developed into a persistent fault which identified as EGR valve and was later confirmed by independent specialist.

Hi.

Appreciate the feedback, I'll talk to the garage re the EGR valve.

The OBD code that comes up is P0238, which would suggest that there is high input to the turbo boost sensor A (?) Hence the initial replacement of the sensor.  Unfortunately, something else is spiking the voltage.

I will talk to the garage again on Monday.

My 2012 4x4 170 Tdi did this and it had the following replaced under warranty :-

 

new turbocharger

new EGR cooler

 

Then it turns out that my DPF was blocked!  Only had to pay 50% to have the DPF cleaned (which sorted it) but still was £350....