engine AUDI A4 1999 B5 / 1.G ATW Engine Oxygen Sensor Control User Guide
Page 32 of 37
24-102
- Start engine.
Specification: approx. battery voltage,
possibly fluctuating
Note:
At certain operating points, the ECM "pulses"
the Ground (GND) for oxygen sensor heating.
This means that the Ground (GND) is
constantly switched on and off at these points.
It is therefore possible that the voltage
displayed on the tester will fluctuate.
When the ECM switches oxygen sensor heating
on and off can be observed, if necessary, via
the function "read measuring value block"
display group number 041.
If there is no voltage:
- Connect multimeter for voltage measurement as
follows:
Harness connector
Terminal
Measure to
1 (B+) Vehicle Ground (GND)
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Page 34 of 37
24-103
If there is no voltage again:
- Check wire connection from terminal 1 of
connector to Fuel Pump (FP) relay via fuse for
open circuit:
Electrical Wiring Diagrams, Troubleshooting &
Component Locations If voltage supply is OK:
If there is no voltage: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure
to
2 (Ground -GND- activation of Engine Control Module -
ECM-) B+
- Start engine.
Specification: approx. battery voltage, possibly fluctuating
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
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Page 35 of 37
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Oxygen Sensor (O2S) heater -Z19- for oxygen sensor before catalytic
converter:
Oxygen sensor heater 1 -Z29- for oxygen sensor behind catalytic
converter:
If wire connection is OK, but there is no Ground (GND) supply for oxygen
sensor heating: - Check following wire connection for open circuit:Harness connector
Terminal
VAG1598/31 test box
Socket
2 5
Harness connector
Terminal
VAG1598/31 test box
Socket
2 63
- Repair open circuit if necessary.
- Replace Engine Control Module (ECM) Page 24
-23
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