1998 AUDI A4 ignition

24-89

If the specified values in display fields 1
and/or 3 do not match the specifications, or if
the readout does not fluctuate by at least 2
%:

- Check oxygen sensor heater Page 24
-114
.

- Check oxygen sensor signal wire and activation
Page 24
-122
.

- Check intake system for leaks and eliminate
false air Page 24
-76
.

- Check fuel pressure regulator Page 24
-33
.

- Fuel return line kinked or plugged.

-
Press button.
- Press button -0- and -6- to select function "End
Output" and confirm with -Q- button.

- Switch ignition off.
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24-119

- Start engine.

Specified value: approx. battery voltage
(fluctuating)

Note:
At certain points in the operating range the
engine control module continuously "switches"
the Ground (GND) connection to the oxygen
sensor heater. That means, it repeatedly
connects and disconnects the Ground (GND)
connection at these points. For this reason the
voltage reading on the tester may fluctuate.

- Switch ignition off.
If there is no voltage reading:

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.

- Check for open circuits in the following wiring connection:
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24-122

Oxygen sensor signal wire and
activation, checking


Note:
The oxygen sensor signal is monitored by the
OBD system.

- Check DTC memory Page 01
-15
.

- If a oxygen sensor malfunction is displayed and
the oxygen sensor heater is OK, disconnect
harness connector for relevant oxygen sensor.
Component location of 4-pin harness connector
of oxygen sensor Page 24
-5 .

If the Specified value is not obtained, check oxygen sensor wiring: - Test voltage by connecting hand-held multimeter Fluke 83 (or
equivalent) (measuring range 2 V) between sockets 3 and 4 of
connector on wiring harness.
-
Switch ignition on. Specified value: 450 50 mV. Bank 1, Sensor 1 Page 24
-123
.
Bank 1, Sensor 2 Page 24
-125
.
Bank 2, Sensor 1 Page 24
-127
.
Bank 2, Sensor 2 Page 24
-129
.
Pa
ge 50 of 61 Ox
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en sensor control, checkin
g
11/22/2002 htt
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play?action=Goto&t
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e=re
pair&id=AUDI.B5.FU04.24.2