Volkswagen Passat 1995 Official Factory Repair Manual page 1629

Diagnostic Trouble Code (DTC) table
Scan Tool Display
00640 3434
Heated Oxygen sensor
relay -J278
Short circuit to
positive
Open circuit/short
circuit to ground
01025
MIL lamp activation
faulty
Short circuit to
positive
Open circuit/short
circuit to ground
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Possible cause
Wiring has short circuit to
positive
Open circuit or short
circuit to ground in wiring
Wiring has short circuit to
positive
MIL lamp faulty
Open circuit or short
circuit to ground in wiring
Corrective steps
Check J278 Page 01-31
Diagnostic Test Mode
Locate short circuit using wiring
diagram and correct as necessary
Check wiring to J278
44 , test step Fig. 5
Check wiring together with MIL lamp
Page 01-44 , test step Fig. 6
Replace MIL lamp if necessary
Page 16 of 23
01-22
, Output
Page 01-
6/12/2004