check engine AUDI A6 1998 C5 / 2.G AEB Engine Motronic MFI And Ignition System

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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24-44

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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24-51

Oxygen Sensor (O2S) aging, checking


Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable

Test requirements
Engine Coolant Temperature (ECT) at least
85 C (185 F)
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24-53


Display fields

1 2 3 4
Display group 34: Oxygen sensor aging (time period check of oxygen sensor)
Display xxxx RPM xx.xx ms xx.xx s Test OFF/Test ON
B1-S1 OK/B1-S1 n.OK
Indicates Engine speed
(in 40 RPM steps) Engine load Time period oxygen sensor Diagnostic status
Diagnostic result
Range 0-6800 RPM 0.00-8.50 ms 0.00-5.00 s ---
Specified value 1800-2200 RPM 0.8-2.0 ms 0.00-3.30 s B1-S1 OK

--- --- If not as specified Page 24
-54
, Continuation
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24-55

Engine operating conditions (engine
electronics), checking


Note:
This test checks whether the Motronic Engine
Control Module (ECM) -J220- recognizes the
engine operating conditions.

Required special tools and test equipment

VAG 1551 or VAG 1552 scan tool with VAG
1551/3 adapter

Test requirements
Engine oil temperature at least 80 C (176
F)

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.
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24-56

- Check engine operating conditions (display field
4):

Display fields

1 2 3 4
Display group 5: Engine electronics-operating conditions
Display xxx RPM xx.xx ms xxx km/h Idle
Part throt
Full throt
1)

Decel
Enrich
Indicates Engine speed
(in 40 RPM steps) Engine load Vehicle speed Operational condition
Range 0-6800 RPM 0.00-8.50 ms --- ---
Specified value 760-960 RPM 0.50-1.50 ms 0 km/h Idle: "Idle"
Throttle slightly open: "Part throt"
Throttle quickly closed: "Decel"
Quick acceleration over 3000 RPM: "Enrich"
1) Possible only while driving
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24-60
Evaluation of display group 2 Display
group: 2


Display field:
2
Possible cause
Corrective action
less than 0.50
ms
Smaller values can only occur while driving during
deceleration
more than 1.50
ms Shift into drive range (auto. transmission)
Engine is affected by additional consumers- Move shift lever to P or N
- Illuminate load (A/C, power steering,
generator)

Poor idle (does not run on all cylinders)- Check spark plugs
- Check fuel injectors Page 24
-87


Throttle valve control module -J338 faulty- Check throttle valve control module
Page 24
-99

Display field:
4
Possible cause
Corrective action
less than 1.8
g/s
Large amount of false air between intake air duct and
Mass Air Flow (MAF) sensor - Check intake air system for leaks (false
air) Page 24
-97

larger than 4.0
g/s
Shift lever in drive range (auto. transmission)
Engine affected by additional consumers- Move shift lever to P or N
- Eliminate load (A/C, power steering,
generator)
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24-63

Engine Coolant Temperature (ECT)
sensor, checking


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
Engine cold
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24-64

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched on) 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-, -0- and -1- to input display group number 1, and
press -Q- button to confirm input.
Read Measuring Value Block 1 1 2 3 4

Indicated on display (1-4 = display fields)
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24-65

- Compare display with specified value for engine
coolant temperature sensor (display field 2):

Display fields

1 2 3 4
Display group 1: Basic function, engine idle speed
Display xxxx RPM
xxx.x C
xx.x% XXXXXX
Indicates Engine
speed
(in 40 RPM
steps) Engine coolant temperature Oxygen sensor control Adjustment
conditions
Range 0-6800
RPM -46.5 to 141.0 C
-25.0 to 25.0 % ---
Specified
value 0 RPM
approx. ambient temperature
1)
Between -10.0 and 10.0%, value
must fluctuate by at least 2 % ---

--- If not as specified Page 24
-66
,
Evaluation of display group 1
--- ---
1) If indicated temperature deviates significantly from the ambient temperature, check ECT sensor wiring for resistance or
open circuits.

- Start engine and let run at idle.

Temperature value must increase evenly
Pa
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