1996 AUDI A4 check engine

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Display fields

1 2 3 4
Display group 004: Coolant temperature, engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C

Specified value xxxx/min 12.0 to 15.0
V Temperature value must rise
evenly From ambient temperature up to
110 C
If display field 3 does not have a realistic
indication:

- Disconnect connector at coolant temperature
sensor.

Coolant temperature sensor with square
connector:

- Connect multimeter between terminal 1 and 3 of sensor for resistance
measurement.
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If specified value is obtained:

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

Coolant temperature sensor with square
connector:

Coolant temperature sensor with oval connector: - Check following wire connections for open circuit and short circuit to
Ground (GND) and B+: Harness connector
Terminal
VAG1598/31 test box
Socket
1 (signal) 93
3 108

- Check following wire connections for open circuit and short circuit to
Ground (GND) and B+: Harness connector
Terminal
VAG1598/31 test box
Socket
3 108
4 (signal) 93
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All models:

- Check both wires to each other for short
circuit.

- Repair open circuit or short circuit if
necessary.
If no malfunctions are found in wires:

- Replace Engine Control Module (ECM) Page
24
-23

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Test requirements:

Fuses for engine electronics OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Battery voltage at least 12.7 V
Generator OK

Test sequence

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

- Switch ignition on.

Note:

The plus voltage supply for the Engine Control
Module (ECM) travels via terminal 3 and 121
(terminal 15) as well as terminal 62 (terminal
30).

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Ground (GND) supply of the Engine Control
Module (ECM) travels via connector terminal 1
and terminal 2.
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- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
1 B+
2 B+
62 Engine Ground (GND)


Specification: approx. battery voltage

- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
3 Engine Ground (GND)

- Switch ignition on.


Specification: approx. battery voltage
If specified values are not obtained:
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- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
121
1)

Engine Ground (GND)

1) The motronic Engine Control Module (ECM)
power supply relay -J271- continues to direct
current to terminal 121 of the Engine Control
Module (ECM) for up to 15 minutes after ignition
is switched off.

- Switch ignition on.


Specification: approx. battery voltage
If specified value is not obtained:

- Check wire connections.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

-
Check motronic Engine Control Module (ECM)
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Knock recognition control stop,
checking

If a DTC is stored regarding "Knock control
regulation limit reached":

- Perform following tests:

Possible cause
Corrective action
DTC for all cylinders

Poor fuel quality
Operating instructions - Change fuel quality
or
Cylinder 1/2 or 3/4
Knock sensor tightened to incorrect torque- Loosen knock sensors and tighten to 20 Nm

Knock sensor faulty- Check knock sensor Page 28
-41


Corrosion at harness connector- Check harness connector

Engine accessories loose- Secure engine accessories
DTC for one Cylinder
Engine damage- Check compression pressure

Engine accessories loose- Secure engine accessories
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