Before Three Way Catalytic Converter
HEATED OXYGEN SENSOR BEFORE THREE WAY CATALYTIC CONVERTER AND OXYGEN SENSOR CONTROL, CHECKING
Special Tools, Testers And Auxiliary Items
- VAG 1551/1552 scan tool with VAG 1551/3 adapter cable
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- Connector test kit VW 1594
- Wiring diagram
Test Conditions
- Coolant temperature at least 80 °C (176 °F)
Functional Check
- Engine running at idle
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press buttons -0-, -2- and -5- to input display group 025 and press -Q- button to confirm input.
Indicated on display (1-4 = Display fields)
Read Measuring Value Block 25 ->
1 2 3 4
- Check the specifications for O2S control (before three way catalytic converter) in display fields 1-3.
If the specification in display field 1 is not attained, or the value does not fluctuate at least 2%:
- Carry out a test drive to remove possible residue on HO2S and repeat check.
If the the specification in display field 1 is not attained even after a road test, or the value does not fluctuate at least 2%:
- Check O2S heating. Oxygen Sensor Heating, Checking
If the value displayed in display field 1 remains constant:
- Press -C- button.
- Press buttons -1-, -1- and -5- to input display group 115 and press -Q- button to confirm input.
Indicated on display (1-4 = Display fields)
Read Measuring Value Block 115 ->
1 2 3 4
- Note HO2S voltage in display field 3.
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
Evaluating Display Group 025:
Evaluating Display Group 115:
Relevance Of Values In 8-digit Number Block:
Checking Basic Voltage
- Separate 4-pin connector (black) -1- to HO2S -G39- (before three way catalytic converter).
- Connect multimeter with test leads from VW 1594 to measure voltage between terminals 3 and 4 (ECM side of harness connector).
- Start engine and measure the basic voltage.
Specification: 0.40 - 0.50 volts
- Switch ignition off.
If the specification is not attained:
- check HO2S wiring.
If the specification is attained:
- Replace HO2S -G39- (before three way catalytic converter).
Checking Heated Oxygen Sensor (HO2S) Wiring
- Connect VAG 1598/18 test box to ECM wiring harness.
- Separate 4-pin connector -1- (black) to H02S -G39- (before three way catalytic converter).
- Check wiring between test box and 4-pin connector for open circuit according to wiring diagram (ECM side of harness connector).
- Terminal 3 and test box socket 42
- Terminal 4 and test box socket 20
Resistance: maximum 1.5 Ohms
- Additionally, check wiring at 4-pin connector for short circuit to one another.
Terminal 4 and test box socket 42
Specification: Infinity Ohms
- Check shielding for short circuit to HO2S wiring according to wiring diagram.
- Terminal 4 and test box socket 56
- Terminal 3 and test box socket 56
Specification: Infinity Ohms
If no wiring malfunction is detected:
- Replace ECM -J220-.
- Read the readiness code. If DTC memory has been erased, repair must be verified via appropriate display group See Readiness code, creating. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection