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Ok chaps I need your combined help my son In law ran the codes on my A4 2.0ltr Tdi SE it came back glow plug module (emissions light on ) I renewed the module cleared fault ,started the car engine cold it took about 20secs to fire , I did a resistance check on the glow plugs no 1& 2 191ohms no.3 & 4 .06 ohms so I changed all 4 with own parts .cleared the fault code again lo and behold emission light back on HELP 

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Hello Derek,

In the absence of other replies, I wonder if clarification on some of the following may help:- 

When you say '... changed all four with .....own...parts.' - is the ...own... a misprint for new? 

If new, or not, have you measured the resistance on the replacements? Unfortunately, assuming new = serviceable can indeed catch you out. 

Is it now starting quicker than it did? 

If all plugs now have an acceptable low resistance, have you checked the associated wiring? 

Not wishing to rub it in, but having bought a new glow plug module, due to the fault code pointing to that, demonstrates that fault codes may not actually show that the unit is faulty - it could be receiving an incorrect 'signal' from another associated component. It's the old cause and effect rule. 

If all the above check out correctly, then I guess the EML could indicate a separate fault, and if it were mine I would then be booking it for a check out by a trusted local diesel specialist. 

Kind regards,

Gareth.

 

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Sorry I replaced the glow plug module then changed all 4 glow plugs with OEM  plugs cleared fault code started engine emission light back on. No.1 plug had 169 ohms resistance No 2l plug had 191 ohms resistance No 3 & 4  0.4 ohms resistance any ideas why the light still comes on am I missing something a fuse perhaps ?

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OK Derek - for ..own... read OEM then - predictive text eh! 

Sorry to be a pain, but I'm still a bit confused. The readings you now give are very slightly different from the original post, so are these readings taken on the new plugs? If not, what are the readings now? 

Repeat question, but is the car now starting as it should? 

Kind regards, 

Gareth.

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Those reading are from the OLD glow plugs the new plugs are all 0.3 ohms resistance brand new plugs am going to check the harness tomorrow but also the fuses in the engine bay compartment Ross tech inform me that's the next step

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I might be barking up the wrong tree the intake manifold flap also causes the light to come on

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Hello Derek,

Sorry to be a pain, but you still don't tell us whether the car now starts without a 20 second cranking - so that side of it is sorted and you now only have the EML to sort. 

I think I'm simply repeating, but if it still has delayed starting, then I would be eliminating the glow plug wiring, before moving on to other suspected causes. 

Kind regards,

Gareth. 

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