170 BHP AVANT 2.0 TDI GLOW PLUGS

[wozza_bingbing]

Hello all im new here and im stuck and very worried and hope someone can help me with a problem, I have recently changed glow plugs and the car seems to run smoother but a bit less power and a fault has now come up - P0671 GLOW PLUG CIRCUIT MALFUNCTION, This is on all 4 cylinders now and im worried iv broken my baby. Has anyone ever come across this and have i missed something simple 

[Steve Q]

Have you checked the leads of distributor? 

Cheers

Steve

[wozza_bingbing]

how do i check them?