After Three Way Catalytic Converter (TWC)

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. Testing and Inspection




Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.




Indicated on display
- Press buttons -1-, -1-and -6- to input display group 116 and press -Q- button to confirm input.




Indicated on display (1-4 = display fields)
- Note HO2S voltage (display field 3).





Continuation:
- Perform test drive to remove possible residue from HO2S and repeat the check.

If the specification in display field 3 is not attained even after a test drive:
- Check O2S heating. Oxygen Sensor (O2S) Heating
- Rev-up to above 3000 RPM.

If the value in display field 3 remains constant See evaluating display group 116.

Evaluating display group 116:




Relevance of values in 8-digit number block:




Checking basic voltage:





- Disconnect 4-pin connector -2- (brown) to HO2S 2 -G108- (after three way catalytic converter).

Oxygen Sensor - After TWC:

- Connect multimeter using test leads from VW 1594 to measure voltage at ECM connector terminals 3 and 4.
- Start engine and measure 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 Heated Oxygen Sensor (HO2S) 2 -G108- (after three way catalytic converter).

Checking Heated Oxygen Sensor (HO2S) wiring:





- Connect VAG 1598/18 test box to ECM wiring harness (arrow).





- Disconnect 4-pin connector -2- (brown) to HO2S 2 -G108-- (after
three way catalytic converter).





- Check wiring between test box and 4-pin connector to ECM for open circuit according to wiring diagram.
- Terminal 3 and test box socket 58.
- Terminal 4 and test box socket 13.
Resistance: max. 1.5 ohms.
- Additionally, check wiring to 4-pin connector for short circuit to one another.
- Terminal 4 and test box socket 58.
Specification: infinite ohms.
- Check shielding for short circuit to HO2S wiring.
- Terminal 4 and test box socket 56.
- Terminal 3 and test box socket 56.
Specification: infinite ohms.

If no wiring malfunction is detected:
- Replace Engine Control Module (ECM) -J220-.
- Read the readiness code. If DTC memory has been erased, verify repair via appropriate display group See Readiness code, creating. Testing and Inspection