display AUDI A4 2000 B5 / 1.G APB Engine Oxygen Sensor Control Checking Owner's Guide

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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24-112
Evaluation display group 037 and 038 Display Group:
037/038


Display field: 2
Possible cause
Corrective action
approx.: 0.450 V

Open circuit in wire 4 between oxygen sensor
and control module - Check signal wire and activation Page 24
-
122



Open circuit in wire 3 between oxygen sensor
and control module

Oxygen sensor heater faulty
Oxygen sensor faulty- Check oxygen sensor heater Page 24
-114
- Replace oxygen sensor
greater than
1.100 V
Short circuit to B+ in wire 4 between oxygen
sensor and control module - Check oxygen sensor wiring bank 1 sensor 2
(behind converter) Page 24
-125

smaller than
0.100 V
Short circuit to Ground (GND) in wire 4 between
oxygen sensor and control module
Short circuit between wire 3 and 4- Check oxygen sensor wiring bank 2 sensor 2
(behind converter) Page 24
-129

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24-113

Continuation
If the specified value in display group 037 and
038, display 3 or 4 is not obtained:

- Check exhaust system and catalytic converter
for leaks (check clamps and exhaust for
damage)

- If the difference of the values in measuring
blocks, display fields 3 (oxygen sensor
correction value) is to large (e.g.:+500 ms, -500
ms), it is possible that the oxygen sensor are
interchanged (mixed up).
If none of the causes are identified:

- Replace particular oxygen sensor "before"
catalytic converter.
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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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24-116


Display fields

1 2 3 4
Display Group 042: Oxygen sensor heater, Bank 2 (at idle speed)
Display
xxx kOhm
Htg.bC.ON
xxx kOhm
Htg.aC.ON
Indicates
Bank 2, Sensor 1
Status of
heater Bank 2, 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
specifications are obtained
It can take a few minutes until
specifications are obtained If the specification is not attained:

- Check voltage supply for oxygen sensor heater
Page 24
-117
.

- Check oxygen sensor signal wire and activation
Page 24
-122
.
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24-121
If the wiring is OK but the oxygen sensor heater
still has no Ground (GND) connection:

- Replace particular oxygen sensor.

- Display readiness code Page 01
-101
. The
readiness code must be generated if the DTC
memory was erased Page 01
-105
.
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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
.
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24-131
If no malfunction can be identified in the wiring:

- Replace Motronic Engine Control Module (ECM)
-J220 Page 24
-24
.

- Display readiness code Page 01
-101
. The
readiness code must be generated if the DTC
memory was erased Page 01
-105
.
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