AUDI A8 1998 D2 / 1.G AEB Engine Motronic MFI And Ignition System

24-37

- Compare display and specified values (display
fields 1 and 2):

Display fields

1 2 3 4
Display group 36: Heated Oxygen Sensor (HO2S) behind Three Way Catalytic Converter (TWC)
Display x.xxx V B1-S2 ON
B1-S2 OFF
Indicates Voltage supply to HO2S behind TWC HO2S behind TWC
ON/OFF
Range 0.000-1.000 V ---
Specified value 0.000-1.000 V
(can oscillate slightly) B1-S2 ON

If not as specified Page 24
-38
, Continuation

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24-38

Continuation
If displayed values are NOT OK (not as
specified):

- Road test to condition oxygen sensor (eliminate
possible contamination) and repeat test.
If the values in display fields 1 and 2 are still
NOT OK:

- Check Oxygen Sensor (O2S) heater Page 24
-
43
.

- Briefly accelerate engine over 3000 RPM.
If the value in display field 1 remains constant:
page Page 24
-39
, Evaluation of display group
36.
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24-39
Evaluation of display group 36 Display group:
36


Display field: 1
Possible causes
Corrective action
approx. 0.435
V
Open circuit in wiring -4- between oxygen sensor and ECM - Check basic voltage Page 24
-40
approx. 0.440
V
Open circuit in wiring -4- between oxygen sensor and ECM
approx. 1.085
V Short circuit to B+ in wiring -4- between oxygen sensor
and ECM - Check wiring for oxygen sensor
Page 24
-41

approx. 0.000
V
Short circuit to Ground in wiring -4- between oxygen
sensor and ECM
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24-40

Checking HO2S reference voltage

- Disconnect 4-pin connector (black) for Oxygen
Sensor (O2S) behind Three Way Catalytic
Converter (TWC) -G108-.

If voltage is NOT OK:
If voltage is OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) between harness
connector terminals 3 and 4 (to ECM), using adapter cables from VW
1594 connector test kit.
- Start engine and measure voltage.
Specified value: 0.40 to 0.50 volts
- Switch ignition off.
- Check HO2S wiring Page 24
-41
- Replace HO2S behind TWC -G108-.
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Checking HO2S wiring

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.

- Disconnect 4-pin connector (black) for Heated
Oxygen Sensor (HO2S) behind Three Way
Catalytic Converter (TWC) -G108-.

- Check wiring for open circuit between ECM/test box and 4-pin HO2S
harness connector (to ECM).

Connector terminal 3 to ECM/test box socket 51
Connector terminal 4 to ECM/test box socket 52
Specified value: max. 1.5
- Check wiring for short circuits between terminals of 4-pin connector,
between connector, ECM/test box, and shielding for wiring harness.

Connector terminal 4 to ECM/test box socket 51
Connector terminal 3 to ECM/test box socket 2
Connector terminal 4 to ECM/test box socket 2
Specified value:
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24-42
If wiring is OK:

- Replace Motronic ECM -J220- Page 01
-57
.

- Carry out adaptation of throttle valve control
module to ECM Page 24
-119
.

- Check readiness code Page 01
-59
. If
Diagnostic Trouble Code (DTC) memory has
been erased, or ECM was disconnected,
generate new readiness code Page 01
-62
.
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24-43

Oxygen Sensor (O2S) heater (behind
TWC), checking


Notes:

Harness connector for Oxygen Sensor (O2S)
heater: 4-pin, black
Component locations Page 24
-1

Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
VAG 1598/22 test box
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagram

Test requirements
Fuse for Oxygen Sensor (O2S) heater OK
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Engine Coolant Temperature (ECT) at least
85 C (185 F)
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24-44

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) Page 01
-7 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -4- and -1- to input display group number 41, and
press -Q- button to confirm input.
Read Measuring Value Block 41 1 2 3 4

Indicated on display (1-4 = display fields)
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24-45

- Compare display and specified values (display
fields 3 and 4):

Display fields

1 2 3 4
Display group 41: Oxygen Sensor (O2S) heater, before and after Three Way Catalytic Converter (TWC)
Display
xx.x
Htg.bC.ON/Htg.bC.OFF
xx.x
Htg.aC.ON/Htg.aC.OFF
Indicates Resistance of Oxygen
Sensor (O2S) heater
before TWC O2S heater on
or
O2S heater off
(before TWC) Resistance of oxygen sensor
(O2S) heater
(after TWC) O2S heater on
or
O2S heater off
(after TWC)
Range --- ---
0.0-65.0
---
Specified
value --- ---
4.9-19.9
Htg.aC.ON

--- --- If not as specified Page
24
-46
, Continuation
---
If displayed values are OK (as specified):

-
Press button to advance program
sequence.
-
Press buttons -0- and -6- to select "End Output"
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