A3 8p...engine management light keeps coming on...

[Martin richardson]

Hi... We have a 2006 a3 8p 1.9tdi...254000 miles... Been awesome... Had a few issues but nothing to bad... The engine management light keeps coming on.... Code reader says glow plug wiring circuit.... Changed the wiring under rocker cover for new.... Light still on... It has been on for 2/3 years now.... You can clear code and light goes out... Long enough for an mot!!... There is no difference in performance at all, we could live with this as it will go out long enough for the mot, but would like to try to fix this issue.... Anyone with any ideas? Regards martin

[Stevey Y]

51 minutes ago, Martin richardson said:

Hi... We have a 2006 a3 8p 1.9tdi...254000 miles... Been awesome... Had a few issues but nothing to bad... The engine management light keeps coming on.... Code reader says glow plug wiring circuit.... Changed the wiring under rocker cover for new.... Light still on... It has been on for 2/3 years now.... You can clear code and light goes out... Long enough for an mot!!... There is no difference in performance at all, we could live with this as it will go out long enough for the mot, but would like to try to fix this issue.... Anyone with any ideas? Regards martin

Hi if you have changed the glow plug loom its probably one or all of the plugs are gone that will throw the same code as they are compromising the loom, worst case scenario they will get so knackered one will go open circuit and will really melt your new loom.

Steve.

[cliffcoggin]

Martin.

So many correspondants here have reported glow plug faults from code readers that turned out to be entirely unrelated to glow plugs that I begin to wonder if "glow plug fault" is the default error mode for anything the readers do not understand.

Even if there is a problem with the glow plugs you will not notice any difference in performance because the glow plugs do not operate when the engine is running. Their only role is to help start the engine in cold conditions by raising the temperature of the fuel/air mixture enough for auto ignition to occur.

[RoyC]

1 hour ago, cliffcoggin said:

Their only role is to help start the engine in cold conditions

Diesel Engine Glow Plugs: Not Just For Starting Anymore 

https://www.enginebuildermag.com/2012/01/diesel-engine-glow-plugs-not-just-for-starting-anymore/

[cliffcoggin]

1 hour ago, RoyC said:

 

Thank you Roy. Evidently I am out of touch with modern developments, though modern may not be the best term to use considering the article was written ten years ago in USA, a country whose diesel development tended to be behind Europe.

I have always avoided getting too involved in discussion of anything electronic because of my ignorance of the matter. I guess now it is time to realise my knowledge of modern engines is equally lacking.

[RoyC]

I thought the same as you until last weekend.

I was chatting with my son, who is in the motor trade, and I said " I don't know why my Audi went into limp mode when I was driving, after all, glow plugs only work on start up"

He told me that these days glow plugs come on any time the engine needs them.

[Stevey Y]

5 hours ago, RoyC said:

I thought the same as you until last weekend.

I was chatting with my son, who is in the motor trade, and I said " I don't know why my Audi went into limp mode when I was driving, after all, glow plugs only work on start up"

He told me that these days glow plugs come on any time the engine needs them.

Hi they are also used to help with DPF regeneration, Cifford is thinking of the old post office engines which if the glow plugs failed needed copious amounts of Easystart [Ethanol Aromatic], things have come a long way since the advent of engine management systems and high pressure fuel systems. Your boy knows his stuff.

Steve