1997 AUDI A8 AEB Engine Motronic MFI And Ignition System

Engine Coolant Temperature (ECT) at least
85 C (185 F)
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24-36

Function test

- 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-, -3- and -6- to input display group number 36, and
press -Q- button to confirm input.
Read Measuring Value Block 36 1 2 3 4

Indicated on display (1-4 = display fields)
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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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24-41

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
.
Pa
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port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1