2000 AUDI A4 catalytic converter

01-48

Output on GST and/or
on VAG 1551 scan tool Possible malfunction cause

Malfunction repair
P0155 / 16539
O2 Sensor Heater Circuit
Malfunction (Bank 2
Sensor 1) Harness connector for Oxygen Sensor
(O2S) heater -Z28- (B2-S1) loose or
corroded due to moisture in the harness
connector

- Check harness connector for tight fit and
contact corrosion, if necessary reconnect
and/or clean, installation location page 24
-1

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and check
DTC memory again
MIL Status:
MIL lights up immediately
Wiring connection for Oxygen Sensor
(O2S) heater -Z28- (B2-S1) faulty, or heater
-Z28- faulty

- Check O2S heater -Z28- (B2-S1) page 24
-51


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and check
DTC memory again
For troubleshooting
Display group 040
Engine Control Module (ECM) -J192-
faulty

- Replace and code engine control module
page 01
-265
erase DTC memory and
test drive check DTC memory
Notes:
The heater for the O2S in front of the Three Way Catalytic Converter (TWC) is switched on by the fuel pump relay.
Pa
ge 64 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-49

Output on GST
and/or on VAG 1551
scan tool Possible malfunction cause

Malfunction repair
P0156 / 16540
O2 Sensor Circuit
Malfunction (Bank 2
Sensor 2) Harness connector for Oxygen Sensor (O2S) 2
behind Three Way Catalytic Converter (TWC) -
G131- (B2-S2) loose or corroded due to moisture
in the harness connector

- Check harness connector for tight fit
and contact corrosion, if necessary
reconnect and/or clean, installation
location page 24
-1

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
MIL Status:
MIL lights up
immediately
Wiring connection to Oxygen Sensor (O2S) 2
behind Three Way Catalytic Converter (TWC) -
G131- (B2-S2) faulty, or sensor -G131- faulty

- Check O2S 2 behind three way
catalytic converter -G131- (B2-S2)
page 24
-53


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
For troubleshooting
Display group 041
Engine Control Module (ECM) -J192- faulty

- Replace and code engine control
module page 01
-265
erase DTC
memory and test drive check DTC
memory
Notes:
The malfunction "P0156 / 16540" is set 123 sec after engine start, at a coolant temperature over 80 C (176 F) and 45 sec
Pa
ge 65 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

after the probe heater behind the Three Way Catalytic Converter (TWC) is switched on , as soon as the signal voltage during
a deceleration fuel shut off is greater than 300 mV. The length of the deceleration fuel shut off must be longer than 4 sec.
Pa
ge 66 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-50

Output on GST and/or
on VAG 1551 scan
tool Possible malfunction cause

Malfunction repair
P0158 / 16542
O2 Sensor Circuit High
Voltage (Bank 2 Sensor
2) Harness connector for Oxygen Sensor (O2S) 2
behind Three Way Catalytic Converter (TWC) -
G131- (B2-S2) loose or corroded due to moisture
in the harness connector

- Check harness connector for tight fit
and contact corrosion, if necessary
reconnect and/or clean, installation
page 24
-1

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
MIL Status:
MIL lights up
immediately
Wiring connection to Oxygen Sensor (O2S) 2
behind Three Way Catalytic Converter (TWC) -
G131- (B2-S2) faulty, or sensor -G131- faulty

- Check O2S 2 behind three way
catalytic converter -G131- (B2-S2)
page 24
-53


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
For troubleshooting
Display group 041
Engine Control Module (ECM) -J192- faulty

- Replace and code engine control
module page 01
-265
erase DTC
memory and test drive check DTC
memory
Notes:
The malfunction "P0158 / 16542" is set 3 min after engine start, as soon as the O2S voltage is greater than 1.4 volts for
Pa
ge 67 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-51

Output on GST and/or
on VAG 1551 scan tool Possible malfunction cause

Malfunction repair
P0161 / 16545
O2 Sensor Heater Circuit
Malfunction (Bank 2
Sensor 2) Harness connector for Oxygen Sensor
(O2S) heater -Z30- (B2-S2) loose or
corroded due to moisture in the harness
connector

- Check harness connector for tight fit and
contact corrosion, if necessary reconnect
and/or clean, installation page 24
-1

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
MIL Status:
MIL lights up immediately
Wiring connection for Oxygen Sensor
(O2S) heater -Z30- (B2-S2) or heater -Z30-
(B2-S2) faulty

- Check O2S heater -Z30- (B2-S2)
page 24
-55


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
check DTC memory again
For troubleshooting
Display group 040
Engine Control Module (ECM) -J192-
faulty

- Replace and code engine control
module page 01
-265
erase DTC
memory and test drive check DTC
memory
Notes:
The heater for O2S behind Three Way Catalytic Converter (TWC) is not switched on immediately at engine start, but only
when the calculated exhaust gas temperature exceeds 308 C (586 F) ( Read measuring value block, display group 42,
channel 1).
Pa
ge 69 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-64


Combustion misfiring has been stored in the DTC
memory for several or all cylinders

- Leaks in intake system check intake system for air
leaks - Fuel pressure not OK Check system and residual
pressure page 24
-20

- Exhaust gas recirculation too high check EGR
system hoses and components - Carbon deposits on fuel injectors check- Carbon deposits on intake valves

Malfunction cause found: Yes


- Erase DTC memory, test drive and check DTC
memory
Notes:

The malfunction "P0300 / 16684" is set as soon as combustion misfiring has been recognized in more than one cylinder.
If there is combustion misfiring with low misfiring rate, the MIL is only set after two successive trips without preceding cold
start and the malfunction occurring.
Combustion misfiring with high misfiring rate is displayed immediately by the MIL blinking, since the Three Way Catalytic
Converter (TWC) can be damaged. In this case, driving should be continued with reduced power and the malfunction
should be repaired as quickly as possible.
Pa
ge 88 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-67


Combustion misfiring on several or all cylinders
stored in the DTC memory

- Leaks in intake system check intake system for air
leaks - Fuel pressure not OK check system and residual
pressure page 24
-20

- Exhaust gas recirculation too high check EGR system
hoses and components - Carbon deposits on fuel injectors check- Carbon deposits on intake valves check

Malfunction cause found: Yes


- Erase DTC memory, test drive and check DTC memory
Notes:

The malfunction "P0300 / 16684" is set as soon as combustion misfiring has been recognized on one or more cylinders.
If there is combustion misfiring with low misfiring rate, the MIL is only switched on after two successive trips without
preceding cold start and malfunction occurring.
Combustion misfiring with high misfiring rate is displayed immediately by the MIL light blinking since the Three Way
Catalytic Converter (TWC) can be damaged. In this case, driving should continue with reduced power and the malfunction
should be repaired as quickly as possible.
Pa
ge 91 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1

01-79

Output on GST and/or on
VAG 1551 scan tool Possible malfunction cause

Malfunction repair
P0422 / 16806
Main Catalyst Efficiency
Below Threshold (Bank 1) Are other malfunctions stored in the DTC
memory?

No

Yes

- First correct these malfunctions
according to Diagnostic Trouble Code
(DTC) table.
MIL Status:
MIL lights up after 2 Trips Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
after test drive, check DTC memory
again

Bank 1 Three Way Catalytic Converter
(TWC) chemically or thermally aged or
mechanically destroyed

- Replace Three Way Catalytic
Converter (TWC) Bank 1
For troubleshooting
Display groups 035, 036,
044
Malfunction cause found: Yes


- Erase DTC memory, test drive and
after test drive, check DTC memory
again
Note:

With the help of the Oxygen Sensor Probe in front of and behind the Three Way Catalytic Converter (TWC), the rate of
Three Way Catalytic Converter (TWC) deterioration is determined using the Three Way Catalytic Converter (TWC) oxygen
storage capability.
Pa
ge 107 of 366 On Board Dia
gnostic
(OBD
) - Multi
port Fuel In
jection
(MFI
)
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU01.01.1