Emmissions Workshop - 2004 Skoda Superb TDI

oconnelldav

Last December 2010 during the big freeze, the EPC (engine) warning light came on with the message 'Emmissions Workshop'. I went to a non Skoda garage who connected it up to the computer and the message was a coolant sensor problem. He fitted a new sensor in January 2011 and reset the light. It came back on 3 weeks later. He fitted another sensor and the light came back on again 4 weeks later. I went to a Skoda garage in June 2011 who told me it was either the wiring to the ECU or the ECU iteself. They ran new wiring bypassing the loom directly into the ECU. The light came back on 2 days later. I bought a second hand ECU off the net and they coded it and fitted it for me. Two days later, message on again. €600 down the toilet and I'm no better off. I can't be sure if the sensor put in by the non Skoda garage was a genuine part so I'm going back to get this done from Skoda for another €100. If this doesn't work, they don't know where to go. I have seen some blogs mentioning glo plug problems so I might get this checked if new sensor doesn't work out. The glo plug light is not on though. I won't be touching another VAG car in my life I can tell you. Who needs the hassle......Any ideas anyone?

Neilw

Get someone with vcds to scan it and post the results/fault codes.

crosshair1

Youve replaced the sensor, wiring and ecu...
There is nothing else!
Post up the fault code present please

bmwkildare2011

To be honest its normaly always the coolent temp sensor and ive never saw a spurious one give trouble also i wouldnt be payin 100 euro for tgat sensor they can be bought for 25e

oconnelldav

Thanks for feedback all. I haven't got the exact fault code or description yet but will try to get it this Friday and post it. The sensor is €35 from the dealer and another €60 to fit. You know what these dealers are like with their labour costs. I wouldn't chance it myself as me under the bonnet would be the same as me looking into a hole in the ground . I'm not convinced this will sort it out but there's eff all left to replace! Thanks again all.......

oconnelldav

I got the error checked out and it is the temperature sensor again. I'm going to get a new Skoda one fitted next week and if that doesn't work then I'm going to get the glo plugs replaced and if that doesn't work then I'm off out to Howth head with it and see if it floats........

DubDani

Had the same Issue on a Superb 1.9TDI, and in the end it was the Fuel temp sensor and the plug connecting it. Replacing both (£10) solved the Issue.

Same as you I also had the coolant sensor replaced initially, but light come back shortly afterwards.

turbodiesel

If the car is running fine how about

A - do nothing

B - buy a code reader for well under a hundred quid and clear the codes yourself.

oconnelldav

Thanks for the tip DubDani. I'll give it a shot and see what happens. I'm trying to sell the car so I need to sort this out first.

AndrewBond

In some cases it might be other problem apart from coolant sensor or its circuit that is setting off the fault code. For example, if you getting fault code like "circuit open" its more like system (ECU) detects high voltage on sensor input and more likely is a circuit itself is at fault. If fault code says something like "coolant sensor circuit - coherence" than, while you still have coolant sensor mentioned indicates that sensor responce is not what system expects from it, but it is very likely to be caused by some other factor rather than sensor itself (or relevant circuit).
Its quite difficult to give you any useful advice without knowing your fault code and freeze frame data, but I suspect all your mechanics were looking in wrong direction. Did anyone ever checked sensor resistance from ECU socket before rushing into ECU replacement job???

Fishtits

AndrewBond wrote: »

In some cases it might be other problem apart from coolant sensor or its circuit that is setting off the fault code. For example, if you getting fault code like "circuit open" its more like system (ECU) detects high voltage on sensor input and more likely is a circuit itself is at fault. If fault code says something like "coolant sensor circuit - coherence" than, while you still have coolant sensor mentioned indicates that sensor responce is not what system expects from it, but it is very likely to be caused by some other factor rather than sensor itself (or relevant circuit).
Its quite difficult to give you any useful advice without knowing your fault code and freeze frame data, but I suspect all your mechanics were looking in wrong direction. Did anyone ever checked sensor resistance from ECU socket before rushing into ECU replacement job???

IMHO, this man speaks sense.

Just because the "Computer" says there is a problem with "X" doesn't mean its the sensor, ie "X". It means that the diagnostic end of things is not happy with what it "see's" from said sensor. It may be a wiring issue, or several other things.

The "computer" offering should always be cross checked with basic fault finding - ohm meter checks of sensors etc. before a definitive diagnosis can be reached.

Sounds all very well... but.

How many of you guys would pay 10 hours labour to track down a wiring fault that turned out to be a bad connection?

I see this every day. People get offended when I'm not interested in fixing the drivers window in a '99 Marea...

Ce le Vie...

AndrewBond

Fishtits wrote: »

How many of you guys would pay 10 hours labour to track down a wiring fault that turned out to be a bad connection?

Sure we both know what you are talking about;). Its a tough business, but if you want to be succesful in it just don't spend 10 hours, think faster.

oconnelldav

Hi All, thanks for all your input. I'll try and get the exact code and description, but I have found that the VAG software gives a very specific code and description that seems to me to be more accurate then a spurious code reader.

@Dubdani, can I ask you to let me know exactly what this plug is that you mention so I can explain to my mechanic?

@AndrewBond, nobody checked resistance that I'm aware of. I sometimes wonder whether these dealerships even know how to do that.

@Fishtits, I think you're right that it's not always X even if it says X. I have seen other threads that mention faulty glo plugs causing this.

At the moment I can see myself pissing another €300 into this car and I've no guarantee that it'll sort it out.

AndrewBond

oconnelldav wrote: »

@AndrewBond, nobody checked resistance that I'm aware of. I sometimes wonder whether these dealerships even know how to do that.

Good mechanics are expensive, apprentices are cheap, economy is tough - now guess who gets employment in dealerships

Plug

Its a simple circuit. Two wires going from the sensor back to the ecu. One wire supply's the sensor with 5 volts. Get them to check the wires.

oconnelldav

Hi Plug,

Thanks for your response. They've rewired it completely from the circuit to the ECU bypassing the loom. It must be something else. Any other ideas?

oconnelldav

I got the glow plugs checked today. 3 out of 4 were not working. Got them replaced. Reset the error. Error came back 30 minutes later. That's the glow plugs ruled out. I got the VAG code and error description today. P1256 (Engine Coolant Temparature Circuit Open/Short to B+). Any ideas anyone?

Row

Can you view the coolant temp on live data....??
If so does it look as it should..?

just found this on google...:)
http://wiki.ross-tech.com/wiki/index.php/17664/P1256

AndrewBond

It may sound complicated, but what has to be done is to check sensor resistance from ECU connector, not just sensor resistance itself. OR (actually this is even better) check voltage on coolant sensor input pin (wire) at the ECU connector (with ignition ON). You need wiring diagram for it (go to https://erwin.skoda-auto.cz/), ECU connector probably is fairly difficult to access for backprobing and you have to be very careful by not to damage wiring or connector sealing, but that is the first step and the most correct check of the sensor circuit condition. If there is 5V (most likely value for sensor signal reference voltage) on that input that would be an indication of open circuit, which could be in the wire from ECU to the sensor, in the sensor itself or at its connector or in RETURN wire (most likely that sensor has two wires going to it).

oconnelldav

I got a new coolant sensor fitted by Skoda garage on Friday and the light has gone out and no sign of it back in 3 days. Usually it would come on after 1 day. He handed me the coolant sensor that he replaced and low and behold, it looked like the original one. It was black and had the VAG symbols on it. If a new one was fitted back in January it would have been green because all the new ones are green. So I've had all the expense and bother because of M1 Motors who are obviouly lying b*******s as I paid them to fit a new one back in January. Don't go near those gangsters boardies. I'll be paying them a visit soon and I'll be seeing them in court. You can't let people away with charging you for a service like that. As one of you said, good mechanics who you can trust are hard to find. Thanks for all your advice everyone. Hopefully, that's the end of it.