1996 AUDI A4 check engine

24-109


Display fields

1 2 3 4
Display group 037: Diagnostic oxygen sensor control (Bank 1)
Display xxx % x.xxx Volt xxx ms
Test ON
Indicated Engine
load Oxygen sensor voltage behind
catalytic converter, Bank 1 Correction value between
oxygen sensor 1 and sensor
2, bank 1 Diagnostic condition
Work
range 15.0 -
175.0 % 0.000 - 1.000 V -1200 - 1200 ms
Test OFF
Test ON
SYST. OK
SYST. not OK
Specified
value 15.0 -
25.0 % 0.000 - 1.000 V -500 - 500 ms
SYST. OK
Note

If specified value is not
obtained: Evaluation display
field 2 Page 24
-112

If specified value is
obtained: Continuation
Page 24
-113

If "SYST. not OK" is
displayed: Check DTC
memory Page 01
-15

or Continue Page 24-113

Note for display field 3:
Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is the
primary control. It corrects slight changes in the mixture (i.e. enrichment or thinning) by holding the oxygen sensor control
before catalytic converter at its higher or lower point for a specific time (duration). If this time is in the positive range (i.e. 50
ms), mixture is shifted in the -enrich- direction. If this time is in the negative range (i.e. 50 ms), mixture is shifted in the -lean-
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24-111


Display fields

1 2 3 4
Display group 038: Diagnostic oxygen sensor control (Bank 2)
Display xxx % x.xxx Volt xxx ms
Test ON
Indicated Engine
load Oxygen sensor voltage behind
catalytic converter, Bank 2 Correction value between
oxygen sensor 1 and sensor
2, bank 2 Diagnostic condition
Work
range 15.0 -
175.0 % 0.000 - 1.000 V -1200 - 1200 ms
Test OFF
Test ON
SYST. OK
SYST. not OK
Specified
value 15.0 -
25.0 % 0.000 - 1.000 V -500 - 500 ms
SYST. OK
Note
If specified value is not obtained:
Evaluation display field 2
Page 24
-112

If specified value is obtained:
Continuation Page 24
-113

If "SYST. not OK" is
displayed: Check DTC
memory Page 01
-15

or Continue Page 24-113

Note for display field 3:
Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is the
primary control. It corrects slight changes in the mixture (i.e. enrichment or thinning) by holding the oxygen sensor control
before catalytic converter at its higher or lower point for a specific time (duration). If this time is in the positive range (i.e. 50
ms), mixture is shifted in the -enrich- direction. If this time is in the negative range (i.e. 50 ms), mixture is shifted in the -lean-
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24-114

Oxygen sensor heater for oxygen
sensor, checking


Note:
The oxygen sensor heating circuit is monitored
by the On Board Diagnostic (OBD). Check DTC
memory Page 01-15
.

- 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.
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select function "Read Measuring Value
Block" and confirm entry with -Q- button.
Read Measurin
g Value Block
Input display group number XXX

Indicated on display
- Press buttons -0-, -4- and -1- to select "display group number 041" and
confirm entry with -Q- button.
Read Measuring Value Block 41
1
2
3
4

Indicated on display
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24-115

- Adjust engine speed to approx: 3000 RPM

- Check resistance of oxygen sensor heater.

Display fields

1 2 3 4
Display Group 041: Oxygen sensor heater, Bank 1 (at idle speed)
Display
xxx kOhm
Htg.bC.ON
xxx kOhm
Htg.aC.ON
Indicates
Bank 1, Sensor 1
Status of
heater Bank 1, Sensor 2
Status of
heater
Range
Htg.bC.ON
Htg.bC.OFF
Htg.aC.ON
Htg.aC.OFF
Specified
value 0 - 0.5 kOhm
Htg.bC.ON/OFF
0 - 0.5 kOhm
Htg.aC.ON/OFF
Note
It can take a few minutes until
specification are obtained
It can take a few minutes until
specified values are obtained
- Press -C- button.

- Press buttons -0-, -4- and -2- to select "display
group number 042" and confirm entry with -Q-
button.
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24-118

- Operate starter briefly.

Specified value: approx. battery voltage
If there is still no voltage reading:

- Check for open circuit and/or short circuit in
wiring between fuel pump relay and socket 1 on
the relevant oxygen sensor connector (on wiring
harness) via fuse.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If the voltage supply is OK:

- Connect hand-held multimeter (voltage measurement range) between
socket 2 (switched Ground (GND) connection from engine control
module) and B+ terminal using test leads from VAG1594 connector test
kit.
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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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24-123
If Specified value is obtained:

- Replace relevant oxygen sensor.

Checking oxygen sensor wiring for Heated
Oxygen Sensor (HO2S) -G39
Component location of 4-pin harness connector
of oxygen sensor Page 24
-5 .

- Disconnect 4-pin connector (black) for Heated
Oxygen Sensor (HO2S) -G39.

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

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Check following wiring connections for open circuits:
Connector on wiring harness,
socket
VAG1598/31 test box socket

3 51
4 70
Resistance in wiring: max. 1.5 Ohm
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24-124


Electrical Wiring Diagrams, Troubleshooting & Component Locations
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no malfunction is identified in the wiring: - Check wiring also on 4-pin harness connector for short circuits to each
other.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 51
Specified value: infinite ohms (open circuit)- Check shielded wire for short circuit to sensor wiring.
Connector on wiring harness,
socket
VAG1598/31 test box socket

4 32
3 32
Specified value: infinite ohms(open circuit)- Replace Motronic Engine Control Module (ECM) -J220 Page 24
-24
.
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p://127.0.0.1:8080/audi/servlet/Dis
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pair&id=AUDI.B5.FU04.24.2