Engine management light when it's cold

[neil_1821]

Bought my Leon fr home Saturday and the engine management light was on, he said it happens when the weathers cold, didn't seem to affect the car in any way.

Got home, plugged it into my vag com and it threw up an error, cylinder 4 glow plug circuit electrical fault.

Cleared the code Saturday and it's been fine since.

Early start this morning, about 2.5 deg, start the car and engine management lights been on ever since

Cars been re-mapped by jabbasport, not sure if that makes a difference. Went through it's service history and for the last 2 years it's been on diagnostics to clear the fault.

Also had new glow plugs in the last 2 years.

Is this just going to be something I have to live with or could there actually be a fault? Because the car doesn't seem to be affected in anyway, just bugs me when the lights on.

 

[Muttley]

Since this is a glow plug fault it will only affect starting in cold weather.

If the glow plugs are OK then the next suspect is the glow plug harness. It works like a spark plug harness, with connectors up inside the long hoods. First thing to do is check the connectors for any corrosion as even a small resistance will set off the glow plug light.

Give all the connectors a clean using contact cleaner, a long pokey stick with some cloth wrapped round the end, perhaps even a file if there is evidence of much corrosion. The connectors should also make good contact with the glow plug terminal - if you find a loose one you might be able to tighten it up with a careful squeeze.

As a last resort the harness can be changed, but it can be a fiddly job to unwrap the wiring harness all the way back to the nearest connector.

 

[neil_1821]

Thanks for that info, actually makes sense it would be the harness/connectors

I assume the glow plugs are fine otherwise I'd expect it to be very lumpy or to of thrown up other fault codes too.

 

[Muttley]

As I said above, the glow plugs only affect cold starting and in very cold weather the first few minutes of driving. They are on when the glow plug light in the dash display is on, to heat up a cold cylinder head and to help the first inlet charges to burn. There is an afterglow phase which helps reduce pollution as the car warms up.

http://www.w124performance.com/docs/general/glow_plug_info1.pdf
http://www.boschsparkplugs.net/411.asp?pt=1&kw=After glow

I don't think there are any other glow-plug fault codes, but I've not done a comprehensive search for that.