1997 AUDI A4 ATQ Engine Motronic Injection System Servicing Workshop Manual

24-61

Voltage supply for Mass Air Flow (MAF)
sensor, checking

- Disconnect connector from Mass Air Flow (MAF)
sensor.

Note:
Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP)
relay.
If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
3 Engine Ground (GND)
- Operate starter briefly.

Specification: approx. battery voltage
- Check wire connection from terminal 3 of connector to Fuel Pump (FP)
relay via fuse for open circuit and short circuit to Ground (GND):
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24-62

- Repair open circuit or short circuit if
necessary.

Note:
Ground (GND) from the ECM is present at terminal 2 of connector.
If specified value is not obtained: - Connect multimeter to terminal 2 and terminal 3 of connector for
voltage measurement.
- Operate starter briefly.

Specification: approx. battery voltage
- Check wire connections Page 24
-63
.

If specified value is not obtained: - Connect multimeter to terminal 1 and terminal 2 of connector for
voltage measurement.
- Switch ignition on.

Specification: about 5 V
- Check wire connections Page 24
-63
.
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24-63

Check wire connections for Mass Air Flow
(MAF) sensor

Note:
Signal wire is also checked during wire test.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

If wire connection is OK: - Check the following wire connections for open circuit and short circuit
to Ground (GND) and B+: Harness connector
Terminal
VAG1598/31 test box
Socket
1 53
2 27
4 29
- Repair open circuit or short circuit if necessary.
- Also check all wires for short circuit to each other.
- Replace Mass Air Flow (MAF) sensor -G70-.
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24-64

Intake air system, checking for leaks
(unmetered air)


Special tools and equipment

Notes:
VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3BEngine leak detection spray G 001 800 A1The negative pressure in the intake system sucks in the leak detection
spray with the unmetered air. Leak detection spray decreases ignition
quality and performance of the fuel mixture. This causes a reduction in
engine speed and a sharp increase of CO content. It is absolutely necessary to follow the safety precautions listed on the
can.
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24-65

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Engine must run at idle for this.Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Read Measurin
g Value Block
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -0- and -1- to select "display group number 001" and
press -Q- button to confirm input.
Read Measuring Value Block 1
1
2
3
4

Indicated on display: (1 thru 4 display fields) - Make note of engine speed in display field 1.
- Spray intake system parts with engine leak detection spray in a
systematic manner.
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24-66
If engine speed does not change:

-
Press button.Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
If engine speed decreases:
-
Press button.- Press buttons -0- and -6- to select "End output" and press -Q- button to
confirm input.
- Switch ignition off.
- Check sprayed part of intake system for leaks, and eliminate the error.
Pa
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jection s
ystem, servicin
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11/23/2002 htt
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e=re
pair&id=AUDI.B5.FU05.24.1