light AUDI A4 1999 B5 / 1.G AFC Engine On Board Diagnostic Multiport Fuel Injection Owner's Guide

01-52

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

Malfunction repair
P0170 / 16554
Fuel Trim Malfunction (Bank 1) Air leak in the area of the intake
manifold

- Find and repair leak

Malfunction cause found: Yes
No

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

Oil dilution (fuel in the oil) because
of frequent cold starts or driving short
distances

- Check, if necessary do oil change
MIL Status:
MIL lights up after 2 Trips Malfunction cause found: Yes
No

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

Mass Air Flow (MAF) sensor -G70-
supplies false signal

- Check Mass Air Flow (MAF) sensor -
G70- page 24
-81

For troubleshooting Display
groups 005, 007, 009 and 010
Malfunction cause found: Yes
No

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

Oil burning with faulty piston

Repair Manual, 2.8 Liter V6 2V Engine
Mechanical, Engine Code(s): AFC, Repair Group 15
- Check compression pressure

Malfunction cause found: Yes

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01-53

Output on GST and/or
on VAG 1551 scan tool
Possible malfunction
cause
Malfunction repair
P0171 / 16555
System too Lean (Bank
1) Malfunction P0174 /
16558
"System too Lean (Bank
2)"
Also in DTC memory
No

Yes

- If the fuel-air mixture for both cylinder banks is too lean, a
malfunction must be present that leads to incorrect mixture
formation for both banks (B1 and B2) Troubleshooting
according to Diagnostic Trouble Code (DTC) page 01
-57


Malfunction cause found:
Yes
No

- Erase DTC memory, test drive and check DTC memory
again
MIL Status:
MIL lights up after 2
Trips Leak in the exhaust
system for bank 1 up to
Heated Oxygen Sensor
(HO2S) -G39-

- Find and repair leak

Malfunction cause found:
Yes
No

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

Leak in intake system

- Find and repair leak
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01-55

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

Malfunction repair
P0172 / 16556
System too Rich (Bank 1) Malfunction P0175 / 16559
"System too Rich (Bank 2)"
Also in DTC memory
No
Yes

- Fuel pressure too high; check system
pressure and residual pressure page 24
-
20


Malfunction cause found: Yes

No

- Erase DTC memory, test drive and check
DTC memory again
MIL Status:
MIL lights up after 2 Trips Fuel injector (Bank 1) does
not close and/or leaks

- Check fuel injection quantity of fuel
injectors and for leaks page 24
-33

For troubleshooting Display
groups 005, 007, 009 and 010
Malfunction cause found: Yes



- Erase DTC memory, test drive and check
DTC memory again
Note:
If the malfunction "P0172 / 16556" is set, the oxygen sensor control has dropped below the learning value limit in the "lean"
direction, but the (HO2S) still recognizes "mixture too rich".
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01-56

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

Malfunction repair
P0173 / 16557
Fuel Trim Malfunction (Bank 2) Air leak in the area of the manifold

- Find and repair leak

Malfunction cause found: Yes
No

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

Oil diluted (fuel in the oil) because
of frequent cold starts for driving short
distances

- Check and change oil if necessary
MIL Status:
MIL lights up after 2 Trips Malfunction cause found: Yes
No

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

Mass Air Flow (MAF) sensor -G70-
supplies false signal

- Check Mass Air Flow (MAF) sensor -
G70- page 24
-81

For troubleshooting Display
groups 006, 008, 009 and 010
Malfunction cause found: Yes
No
Continued next page

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

Oil burning with faulty piston

Repair Manual, 2.8 Liter V6 2V Engine
Mechanical, Engine Code(s): AFC, Repair - Check compression pressure
Pa
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01-57

Output on GST and/or
on VAG 1551 scan tool
Possible malfunction
cause
Malfunction repair
P0174 / 16558
System too Lean (Bank
2) Malfunction P0171 /
16555
"System too Lean (Bank
1)"
Also in DTC memory
No

Yes

- If the fuel-air mixture is too lean for both cylinder banks, a
malfunction must be present that leads to faulty mixture
formation for both banks (B1 and B2) Troubleshooting
per Diagnostic Trouble Code (DTC) table, page 01
-53


Malfunction cause found:
Yes
No

- Erase DTC memory, test drive and check DTC memory
again
MIL Status:
MIL lights up after 2
Trips Leaks in the intake
system for bank 2 up to
Heated Oxygen (HO2S)
sensor 2 -G108-

- Find and repair leak

Malfunction cause found:
Yes
No

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

Leaks in intake system

- Find and repair leak
Pa
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jection
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01-59

Output on GST and/or on VAG
1551 scan tool Possible malfunction
cause
Malfunction repair
P0175 / 16559
System too Rich (Bank 2) Malfunction P0172 /
16556
"System too Rich (Bank 1)"
Also in DTC memory
No
Yes

- Fuel pressure too high. Check system
pressure and residual pressure page 24
-20

Malfunction cause found:
Yes
No

- Erase DTC memory, test drive and check
DTC memory again
MIL Status:
MIL lights up after 2 Trips Fuel injector (Bank 2)
does not close or leaks

- Check fuel injection quantity and for leaks
page 24
-33

For troubleshooting Display
groups 006, 008, 009 and 010
Malfunction cause found:
Yes


- Erase DTC memory, test drive and check
DTC memory again
Notes:
If the malfunction "P0175 / 16559" is set, the oxygen sensor control has dropped below the learning value limit in the "lean"
direction, but the (HO2S) still recognizes "mixture too rich".
Pa
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jection
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01-60

Output on GST and/or on
VAG 1551 scan tool Possible malfunction
cause
Malfunction repair
P0171 / 16555
System too Lean (Bank 1) Malfunction P1250 /
17658 "Fuel Level Too
Low" also in DTC memory
No
Yes

- For malfunctions that can be caused by fuel problems
(e.g. fuel system too lean), the malfunction "Fuel Level
Too Low" is also set if there is less than 12 liters (12.7 qt.)
fuel in the tank check tank level and fill tank if necessary
P0174 / 16558
System too Lean (Bank 2) Malfunction cause found:
Yes
No

- Erase DTC memory, test drive and check DTC memory
again
MIL Status:
MIL lights up after 2 Trips Large air leak quantity
in intake system to Mass
Air Flow (MAF) sensor -
G70-

- Determine cause of air leak and repair
For troubleshooting
Display groups 005, 006,
007, 008, 009 and 010
Malfunction cause found:
Yes
No
Continued next page

- Erase DTC memory, test drive and check DTC memory
again
Pa
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jection
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01-62

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

Malfunction repair
P0300 / 16684
Random Misfire Detected
_______________________
P0301 / 16685
Cylinder 1 Misfire Detected Malfunction P1250 / 17658 "Fuel
Level Too Low" also in DTC memory
No
Yes

- For malfunctions that can be caused by
fuel problems (e.g. fuel system too lean),
the malfunction "Fuel Level Too Low" is
also set if there is less than 12 liters (12.7
qt.) fuel in the tank check tank level and
fill tank if necessary
_______________________
P0302 / 16686
Cylinder 2 Misfire Detected Malfunction cause found: Yes
No

- Erase DTC memory, test drive and check
DTC memory again
_______________________
P0303 / 16687
Cylinder 3 Misfire Detected
_______________________ Are other Diagnostic Trouble
Codes (DTC) present in the DTC
memory (e.g fuel injector, heated
oxygen sensor probes, fuel system
etc.) when combustion misfiring is
recognized
No Yes

- The combustion misfiring that has been
recognized is a resulting malfunction from
the stored Diagnostic Trouble Codes (DTC)
First repair this malfunction according to
Diagnostic Trouble Code (DTC) table
MIL Status:
MIL lights up or blinks
For troubleshooting Display
groups 031, 038, 039
Malfunction cause found: Yes
No
Continued next page

- Erase DTC memory, test drive and check
DTC memory again
Pa
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jection
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01-65

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

Malfunction repair
P0300 / 16684
Random Misfire Detected
_______________________
P0304 / 16688
Cylinder 4 Misfire Detected Malfunction P1250 / 17658 "Fuel
Level Too Low" also in DTC
memory
No
Yes

- For malfunctions that can be caused by
fuel problems (e.g. fuel system too lean), the
malfunction "Fuel Level Too Low" is also set
if there is less than 12 liters (12.7 qt.) fuel in
the tank check tank level and fill tank if
necessary
_______________________
P0305 / 16689
Cylinder 5 Misfire Detected Malfunction cause found: Yes
No

- Erase DTC memory, test drive and check
DTC memory again
_______________________
P0306 / 16690
Cylinder 6 Misfire Detected
_______________________ When combustion misfiring is
recognized, are there other
Diagnostic Trouble Codes (DTC)
(e.g. fuel injector, Oxygen Sensor
Proben, Fuel system etc.) in DTC
memory
No Yes

- The combustion misfiring that has been
recognized is a resulting malfunction from
the stored Diagnostic Trouble Codes (DTC)
First repair this malfunction according to
Diagnostic Trouble Code (DTC) table
MIL Status:
MIL lights up or blinks
For troubleshooting Display
groups 031, 038, 039
Malfunction cause found: Yes
No
Continued next page

- Erase DTC memory, test drive and check
DTC memory again
Pa
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jection
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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
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gnostic
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jection
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)
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