2000 AUDI A6 AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

24-68

Mass Air Flow (MAF) sensor, checking


Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagram

Test requirements
All electrical consumers switched off (coolant
fan must not run during test).
A/C must be switched off
Fuse for MAF sensor OK
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Test sequence

- Connect VAG1551 or VAG1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) page 01
-8 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -0- and -2- to input display group number 2 (002),
and press -Q- button to confirm input.
Read Measuring Value Block 2 1 2 3 4

Indicated on display (1-4 = display fields)
- Compare display with specified values for engine load (display fields 2
and 4):
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24-70


Display fields

1 2 3 4
Display group 2: Load measurement
Display xxx RPM xx.xx ms xx.xx ms xx.x g/s
Indicates Engine
speed
(in 40 RPM
steps) Engine load Injection
time Mass air flow
Range 0 - 6800
RPM 0.00 - 12.75 ms 0.00 -
20.00 ms 0.0 - 140 g/s
Specified
value 620 - 740
RPM
(all-wheel
drive)
or
740 - 860
RPM
(front-wheel
drive) 1.00 - 2.50 ms 2.00 - 5.00
ms 2.8 - 5.6 g/s

2520 RPM 0.80 - 2.50 ms 1.60 - 5.00
ms 10.0 - 15.0 g/s
--- If not as specified page 24
-71
,
--- If not as specified page 24
-72
,
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Evaluation of display group 2, display
field 2 Evaluation of display group 2, display
field 4
If displayed values are OK (as specified):

-
Press button to advance program
sequence.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- Switch ignition off.
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24-71
Evaluation of display group 2, display field 2 Display group:
2


Display field:
2
Possible malfunction cause
Corrective action
less than 1.00
ms
Smaller values can only occur while driving during
deceleration
more than 2.50
ms Shift lever in drive range (auto. transmission)
Engine is affected by additional consumers- Move shift lever into P or N
- Eliminate load (A/C, power steering, generator)

Poor idle (does not run on all cylinders)- Check and spark plugs page 28
-21
(checking
ignition coils)
- Check fuel injectors page 24
-102


Throttle valve control module -J338- faulty- Check throttle valve control module page 24
-
128

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24-72
Evaluation of display group 2, display field 4 Display
group: 2


Display field:
4
Possible malfunction cause
Corrective action
less than 2.8
g/s
Large amount of false air between intake air duct and
Mass Air Flow (MAF) sensor - Check intake air system for leaks (false
air) page 24
-126

larger than 5.6
g/s
Shift lever in drive range (auto. transmission)
Engine affected by additional consumers- Move shift lever into P or N
- Eliminate load (A/C, power steering,
generator)

Open circuits in wire 1 or 2 between MAF sensor and
ECM - Check voltage supply page 24
-73


Open circuit in wire 3 between MAF sensor and relay
panel - Check wiring page 24
-73
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24-73

Checking voltage supply

If there is no voltage:
Checking wiring - Disconnect 3-pin harness connector from Mass Air Flow sensor (MAF).
- Connect multimeter US1119 (Fluke 83 or equivalent) between harness
connector terminals 2 (Ground) and 3 (B+), using adapter cables from
VW1594 connector test kit.
Specified value: 9.0-14.5 volts
- Switch ignition off.
- Check wiring using applicable wiring diagram.
- Switch ignition off.
- Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Check wiring for open circuits, between ECM/test box and 3-pin MAF
sensor harness connector.

Connector terminal 1 to ECM/test box socket 13
Connector terminal 2 to ECM/test box socket 12
Specified value: max. 1.5
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24-74

- Check wiring for short circuits between terminals
of 3-pin connector, and between connector and
ECM/test box.


Connector terminal 1 to ECM/test box
socket 12

Specified value:

- Switch multimeter to 20 VDC measuring
range.

- Check wiring at 3-pin connector for short circuit
to B+ (battery positive voltage), according to
applicable wiring diagram.


Connector terminal 1 to vehicle Ground

Connector terminal 2 to vehicle Ground

Specified value: 0 volts
If wiring is OK:

- Replace Mass Air Flow sensor (MAF) -G70-.

-
Check readiness code page 01
-70
. If
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