sensor AUDI A4 1995 B5 / 1.G APB Engine Motronic Multiport Fuel Injection System Servising User Guide

24-16


2 -
Disconnect harness connector from EVAP
Canister Purge Regulator Valve -N80.
3 -
Loosen both exhaust temperature
sensors -G235 and -G236 from intake
manifold. The sensors remain connected.
Ensure Ground cable is tight when
installing.
4 -
Loosen hose to brake booster at
bulkhead.
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24-18


Repair Manual, 2.7 Liter V6 5V BiTurbo Engine
Mechanical, Engine Code(s): APB, Repair Group 15
9 -
Disconnect harness connector at Throttle
Valve Control Module -J338.
10 -
Disconnect harness connector at Charge
Air Pressure Sensor -G31.
11 -
Remove indicated pressure hoses 12 -
Loosen indicated hose, this hose leads to
bypass valve.
13 -
Disconnect harness connector at Intake
Air Temperature (IAT) Sensor -G42.
14 -
Loosen indicated hose, (crankcase
ventilation hose).
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24-59

Mass Air FLow (MAF) sensor -G70,
checking


Requirements

Coolant temperature at least 80 C (175 F)

Electrical consumers switched off (radiator
fan must not run during test)
A/C switched off
Fuse for mass air flow sensor OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Checking function

- Connect vehicle diagnostic, testing and
information system VAS5051 or VAG1551 scan
tool and select engine electronics control
module by entering address word "01" Page
01
-9 . When doing this the engine must be at
idle.
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24-61

Note:
Read measuring value block display group 2 as
described in repair manual and evaluate it
Page 24
-69
. If the suggested repair steps refer
to the voltage supply test for the Mass Air Flow
(MAF) sensor or the wiring connections from the
Mass Air Flow (MAF) sensor to the Engine
Control Module (ECM), proceed to the following
pages.
Please note the distinction between sensors
made by Bosch and those made by Hitachi
(recognizable via the writing on the sensor).

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

Note: For Bosch Mass Air Flow (MAF)
sensors see page Page 24
-65
.

- Disconnect connector from Mass Air Flow (MAF) sensor.
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24-62

- Connect multimeter to terminal 2 of connector
and engine Ground (GND) for voltage
measurement.

- Operate starter briefly.

Specification: approx. battery voltage

Note:
Voltage is supplied to Mass Air Flow (MAF)
sensor from Fuel Pump (FP) relay.
If there is no battery voltage.

- Check wire connection from terminal 2 of
connector to Fuel Pump (FP) relay via fuse for
open circuit and short circuit to Ground (GND),
repair if necessary.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
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24-64

Wire connections for Mass Air Flow (MAF)
sensor, checking (Hitachi 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
-20
.

The following wire connections must be checked for short circuit to B+,
Ground (GND) and for open circuit Connector for Mass Air Flow (MAF)
sensor -G70-
VAG1598/31 test box
terminal
1 53
3 27
4 29
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24-65

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

Note:
Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP)
relay.
If there is no battery voltage.
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Disconnect connector from Mass Air Flow (MAF) sensor.
- Connect multimeter to terminal 2 of connector and engine Ground
(GND) for voltage measurement.
- Operate starter briefly.
Specification: approx. battery voltage
- Check wire connection from terminal 2 of connector to Fuel Pump (FP)
relay via fuse for open circuit and short circuit to Ground (GND), repair
if necessary.
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24-67

Wire connections for Mass Air Flow (MAF)
sensor, checking (Bosch 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
-20
.

The following wire connections must be checked for short circuit to B+,
Ground (GND) and for open circuit Connector for Mass Air Flow (MAF)
sensor -G70-
VAG1598/31 test box
terminal
3 27
4 53
5 29
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24-68

Wire resistance: max: 1.5 Ohm

- Also check all wires for short circuit to each
other.

Specification: infinite Ohms (no continuity)

- If the voltage supply and the wire connection are
OK, replace Mass Air Flow (MAF) sensor -G70-.
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24-71
Reading Display Group 002 Display field
4
Possible cause of malfunction
Corrective action
Less than 3.0
g/s
Large quantity of un-metered air between intake manifold
and Mass Air Flow (MAF) sensor
Voltage supply to Mass Air Flow (MAF) sensor or wiring to
Engine Control Module (ECM) - Check intake system for leaks (un-
metered air) Page 24
-76

- Check voltage supply and wiring Page 24
-72

More than 4.5
g/s
Load on engine due to accessories- Eliminate load (A/C, power steering,
generator)

Voltage supply to Mass Air Flow (MAF) sensor or wiring to
Engine Control Module (ECM) - Check voltage supply and wiring Page
24
-72

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port Fuel In
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) system, servicin
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11/22/2002 htt
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play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1