1994 GOLF, HAS CODE 525-NO SIGNAL FROM OXYGEN SENSOR. INSTALLED NEW SENSOR YET INTERMITTETLY WILL TRIP CODE AND FAIL EMISSIONS. SUSPECT ECU, HAVE SIGNAL TO ECU FROM O2 SENSOR. WHEN FAILING CO IS 8% THEN WILL ALL OF A SUDDEN BEGIN TO PASS. WHEN VEHICLE IS FAILI... Login to read more.