check engine AUDI A4 1995 B5 / 1.G AWM Engine Motronic Injection System Servicing Owner's Manual

24-56


If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If specified value is obtained: - Connect multimeter for voltage measurement as follows.Central electronicsin driver-side footwell, left,
position 4
Terminal
Measure to
19 Engine Ground
(GND)
- Switch ignition on.

Specification: approx. battery voltage
- Check wire connections.
- Check the following wire connection for open circuit and short circuit to
Ground (GND) and B+: Central electronicsin driver-side footwell, left,
position 4
Terminal
VAG1598/31 test
box


Socket
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- Repair open circuit or short circuit if
necessary.
If no malfunctions are detected:

- Replace Fuel Pump (FP) relay -J17-.

- Re-connect Engine Control Module (ECM).

Check voltage supply for Fuel Pump (FP) and
components

- Remove fuses S228, S232, and S234 (positions 28, 32, and 34) from
fuse holder.
- Initiate output Diagnostic Test Mode (DTM) Page 01
-51
and activate
Evaporative Emission (EVAP) canister purge regulator valve -N80-.
- Connect multimeter for voltage measurement to Ground (GND) and to
one terminal of the following fuses in the fuse holder. Circlip
Specified value at one of the terminals
S228 approx. battery voltage
S232 approx. battery voltage
S234 approx. battery voltage
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Component location Overview of component
locations Page 24
-5

Test requirements:

Coolant Temperature at least 80 C.

Electrical consumers switched off (radiator
fan must NOT run during test).
A/C switched off.

Checking function

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Engine must run at idle for this.

Display on VAS5051:
- In selection -1-, click on the diagnostic function "04 - Basic setting".
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Evaluation display group 002 Display field:
3
Possible cause
Corrective action
less than 1.0
ms
Smaller values are only possible when driving in
deceleration mode
larger than
4.0 ms Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Poor idle (does not run on all cylinders)- Check spark plugs.
- Check fuel injectors Page 24
-37
.


Throttle valve control module - J338- faulty- Check throttle valve control module
Page 24
-124

Display field:
4
Possible cause
Corrective action
smaller than
2.0 g/s
large false air mass between intake manifold and Mass Air
Flow (MAF) sensor
Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check intake system for leaks (false air)
Page 24
-68
.
- Check voltage supply and wire
connections Page 24
-64

larger than
4.5 g/s
Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check voltage supply and wire
connections Page 24
-64

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

Test requirements:

Fuse for Mass Air Flow (MAF) sensor OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Fuel Pump (FP) relay OK; checking Page 24
-52
.

Note:
Voltage is supplied to Mass Air Flow (MAF)
sensor from Fuel Pump (FP) relay.

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

- Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
2 Engine Ground (GND)
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If specified value is not obtained:

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

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- Repair open circuit or short circuit if
necessary.

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

Specification: approx. battery voltage
- Check wire connections Page 24
-67
.
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Check wire connections for Mass Air Flow
(MF) sensor

Note:
Signal wire is also checked during wire test.

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

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
3 27
4 53
5 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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Intake system, checking for leaks
(unmetered air)


Special tools and equipment

Notes:
Test sequence
VAS5051 with VAG5051/1Engine 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.
- Connect VAS5051 tester Page 01
-7 and select vehicle system "01 -
Engine electronics". Engine must run at idle for this.
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Display on VAS5051:
If engine speed decreases: - Make note of engine speed in display field -1.
- Spray intake system parts with engine leak detection spray in a
systematic manner.
- Check sprayed part of intake system for leaks, and eliminate the error.
-
Press "08 - erase DTC memory" to end function -button.- Select "06 - End Output"
- Switch ignition off.
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