1997 AUDI A8 AEB Engine Motronic MFI And Ignition System

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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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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function 06, and press -Q- button to confirm
input.

- Switch ignition off.
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24-46

Continuation

- Disconnect 4-pin connector (black) for Oxygen
Sensor (O2S) 2 -G108- behind Three Way
Catalytic Converter (TWC).

If resistance is NOT OK:
If resistance is OK: - Connect multimeter US 1119 (Fluke 83 or equivalent) between HO2S
connector terminals 1 and 2, using VW 1594 connector test kit.
- Measure resistance.

Specified value: 0.00-19.9 - Replace Heated Oxygen Sensor (HO2S) behind TWC -G108-.
- Switch multimeter to 20 VDC measuring range.
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If display = Htg.aC.ON:
If display is switching between "Htg.aC.ON" and "Htg.aC.OFF" - Connect multimeter between harness connector terminals 1 and 2 (to
ECM), using VW 1594 connector test kit.
- Measure voltage supply and check display in display group 41, display
field 4.
Specified value: 11.0-14.5 volts Specified value: 0.0-12.0 volts (oscillating)
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24-48
If there is no voltage:

If there is still no voltage: - Connect multimeter between harness connector terminal 1 (to ECM)
and vehicle Ground, using VW 1594 connector test kit.
Specified value: 11.0-14.5 volts
- Check wiring between terminal 1 and relay panel using appropriate
wiring diagram.
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