1999 AUDI A4 fuel pressure

01-82


EVAP canister purge regulator
valve -N80- sticks mechanically

- Check solenoid valve for Evaporative
Emission (EVAP) canister purge -N80- page 24
-58


Malfunction cause found: Yes
No
Continued next page

- Erase DTC memory, test drive and after test
drive, check DTC memory again
For troubleshooting
Display group 030
Sensor for EVAP canister -G172-
(differential pressure sensor) faulty

- Check Sensor for EVAP canister -G172-
(differential pressure sensor) page 24
-61


Malfunction cause found: Yes


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

With the help of the Sensor for EVAP canister -G172- (differential pressure sensor)the pressure is measured between the
Evaporative Emissions (EVAP) canister and solenoid valve for Evaporative Emission (EVAP) canister purge -N80- with
valve closed and open. If the difference in the two pressures is less than 4 mbar to 23 mbar (depending on air pressure),
the malfunction is set.
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01-83

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

Malfunction repair
P0452 / 16836
Evaporative Emission
Control System Pressure
Sensor Low Input Harness connector on sensor for EVAP
canister -G172- (differential pressure sensor)
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

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
after test drive, check DTC memory
again
MIL Status:
MIL lights up immediately Wiring connection to sensor for EVAP
canister -G172- (differential pressure sensor)
faulty, or sensor -G172- faulty

- Check sensor for EVAP canister -
G172- (differential pressure sensor)
page 24
-61


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
after test drive, check DTC memory
again
For troubleshooting
Display group 030
Engine Control Module (ECM) -J192- faulty

- Replace and code engine control
module page 01
-265
erase DTC
memory and test drive check DTC
memory
Note:
The malfunction "P0542 / 16836" is set as soon after engine start as the differential pressure sensor signal is less than 0.1 V
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01-84

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

Malfunction repair
P0453 / 16837
Evaporative Emission
Control System Pressure
Sensor High Input Harness connector on sensor for EVAP
canister -G172- (differential pressure sensor)
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

Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
after test drive, check DTC memory
again
MIL Status:
MIL lights up immediately Wiring connection to sensor for EVAP
canister -G172- (differential pressure sensor)
faulty, or sensor -G172- faulty

- Check sensor for EVAP canister -
G172- (differential pressure sensor)
page 24
-61


Malfunction cause found: Yes
No

- Erase DTC memory, test drive and
after test drive, check DTC memory
again
For troubleshooting
Display group 030
Engine Control Module (ECM) -J192- faulty

- Replace and code engine control
module page 01
-265
erase DTC
memory and test drive check DTC
memory
Note:
The malfunction "P0453 / 16837" is set as soon after engine start as the differential pressure sensor signal is greater than 5.0
Pa
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01-147

Rapid data transfer
Q
03 - Output Diagnostic Test Mode

Indicated on display
- Press -Q- button to confirm input.
Output diagnostic test mode Fuel Pump
(FP) Rela
y -J17

Indicated on display
The fuel pump relay must be triggers and the fuel pump must run; the
flowing noise at the fuel pressure regulator can be clearly heard.
- If fuel pump relay is not triggered, check control page 24
-24
.
-
Press button.
Output diagnostic test mode Idle Air Control
(IAC
) valve -N71

Indicated on display
This valve is triggered (clicks) until moving on to the next output by
pressing the button. - If the valve is not triggered (does not click), check -N71- page 24
-
37
.
-
Press button.
Output diagnostic test mode Intake manifold chan
ge-over valve -N156

Indicated on display
This valve is triggered (clicks) until you move on to the next output by
pressing the button. - If the valve is not triggered (does not click), check intake manifold
change-over valve -N156- page 24
-64
.
-
Press button.
Pa
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01-178
Test table display group 005 and/or display group 006 Display
fields Display on
VAG 1551
scan tool Malfunction cause
Malfunction repair
1, 2, 3, 4 Low oxygen
sensor learning
values
If first learning value in display field 1 is low, but
learning value in display fields 2, 3 and 4 normal:
oil dilution (large amount of fuel in the oil), fuel
injector leaks - Pull off cylinder block breather hose
and close
- If problem disappears after drive on
expressway and/or oil change
- Check fuel injector page 24
-29
If all four oxygen sensor learning values very low
overall:
- Fuel system pressure too high
- EVAP canister purge regulator valve -N80- open
continuously - Check system and residual pressure
page 24
-20

- Check -N80- page 24
-58
and/or
display group 009, display field 3
and/or display group 001, display field
2


Mass Air Flow (MAF) sensor -G70- faulty
Oxygen sensor (O2S) heating faulty or Heated
Oxygen Sensor (HO2S) dirty - Check MAF sensor -G70 page 24
-
81

- Check HO2S and O2S heating
page 24
-49
and/or display group 010,
display fields 1 and 2
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jection
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)
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01-179

Display
fields Display on VAG
1551 scan tool Malfunction cause
Malfunction repair
1, 2, 3, 4 High oxygen
sensor learning
values
If learning value in display field 1 is low, but
learning value in display fields 2, 3 and 4
normal: air leak in manifold area possible
Fuel injector plugged - Repair cause
- Check fuel injector page 24
-29
If all four oxygen sensor learning values are very
high overall:
- Mass Air Flow (MAF) sensor -G70- faulty
- Fuel system pressure too low (fuel supply)
- Intake air leak between sensor -G70- and throttle
body
- Intake air leak in manifold gasket - Check MAF sensor -G70 page 24
-
81
and/or display group 001, display
field 2
- Check system and residual pressure
page 24
-20

- Repair cause


Oxygen sensor (O2S) heating faulty or Heated
Oxygen Sensor (HO2S) dirty - Check HO2S and O2S heating
page 24
-49
and/or display group 010,
display fields 1 and 2
Pa
ge 251 of 366 On Board Dia
gnostic
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) - Multi
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jection
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)
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01-191

Display
fields Display on VAG 1551 scan tool
Malfunction cause
Malfunction repair
3/4 Display does not fluctuate-constant
between 0.0 - 0.3 V and/or between
0.6 - 0.9 V
Fuel injector faulty- Check fuel injectors page 24
-29

Spark plug faultyLarge intake air leak Engine Coolant Temperature
(ECT) sensor -G62- faulty EVAP canister purge
regulator valve -N80- - Check spark plug
- Repair cause
- Check DTC memory page 01
-13

and/or check -G62-
- Check using output diagnostic test
mode page 01
-145
and/or check -
N80-

Heated Oxygen Sensor
(HO2S) -G39- faulty or dirty Oxygen Sensor (O2S) heater
-Z19- does not function - Check DTC memory page 01
-13

and/or check -G39-
- Check -Z19- page 24
-49

Fuel system pressure too
high or too low - Check fuel pressure regulator and
residual pressure page 24
-20


Constant 2.550 V Short to positive (B+) through:
Heated Oxygen Sensor
(HO2S) -G39- wiring Engine Control Module
(ECM) -J192- - Check -G39- page 24
-49Pa
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jection
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01-202
Display group 019 Display shows
Specified display value
Designation/diagnose
Basic setting 19
1 2 3 4 At idle: 1.5 - 3.5% 1 = Momentary engine power (internal computation value)
At 2500 RPM:
6.5 - 9.5%
At idle:
3.0 - 5.5 g/s 2 = Intake air quantity (via mass air flow sensor)
At 2500 RPM:
9.5 - 13.5 g/s
___ km/h 3 = Momentary vehicle speed display group 003, display field 4 _._ m/s 4 = Fuel injection time (average of all cylinders) Note on display field 1:
The momentary engine power is a control module-internal calculated value that is calculated from the amount of air taken in
under normal conditions (air pressure 1013 mbar, air temperature 20 C or 68 F).
Pa
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) - Multi
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)
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yp
e=re
pair&id=AUDI.B5.FU01.01.1