3 weeks ago, thanks to GlowBugTDI, VCDS read my '02 TDI 'MIL' fault codes as:
17055 / P0671 (Cylinder 1 Glow plug circuit (Q10))
17058 / P0674 (Cylinder 4? Glow plug circuit)
17978 / P1570 =?
Now that I've used my cheapo Radio Shack multimeter on glow plug tips:
(coolant side) #1 =3.42 ohms, #2=0.6, #3 =0.5, #4 =1.02 ohms (battery side)
~> so do I at least replace glow plugs #1 and? #4 or all 4? ..or? (before simply buying parts) it seems there's more to check: spray/clean the GP wiring harness caps oxidation? (I have DeoxIT D5, but wasn't yet comfortable severely twisting the harness to enable spraying into caps) ..also test a GP? relay? ..test 'GP' fuses oxidation under battery cover? etc etc.
(for my reference: 2004 TDIclub advice from 'Wingnut/MoGolf') "Take note of the resistance value of each plug. Resistance must be below 1.5 ohms. They should all be between 0.5 and 1.5 ohms. It doesn't matter what the readings are, as long as they are close to each other (within 0.2 - 0.3 ohms). If you have a plug that reads high or infinite, then you have found the bad plug and it needs to be replaced."
Perhaps I should post in main forum, but I'm posting in MN group in case there are local sources for parts: Napa? (save shipping) vs
www.idparts.com/glow-plug-system-c-123_94.html) ..which brand? of glow plug ..OK to mix? ..or first try 'good-enough' used plugs (if I had any)?