1999 AUDI A4 coolant

Engine Coolant Temperature (ECT) at least
85 C (185 F)
Pa
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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)
Pa
ge 67 of 135 Motronic Multi
port Fuel In
jection
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) and i
gnition s
ystem
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24-57

Mass Air Flow (MAF) 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
All electrical consumers switched off (coolant
fan must not run during test).
A/C must be switched off
Fuse for MAF sensor OK
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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
Pa
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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
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24-66
If NOT:

- Replace Engine Coolant Temperature (ECT)
sensor -G62-.

-
Press button to advance program
sequence.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- Switch ignition off.
Evaluation of display group 1 Display group: 1


Display field: 2
Possible cause
Corrective action
approx. -46.5 C
Open circuit or short circuit in wiring to B+ - Check wiring Page 24
-66
approx. 141.0 C
Short circuit to Ground

Checking wiring

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.
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24-68
If wiring is OK:

- Check ECT sensor resistance across terminal 1 (signal) and terminal 3
(ground).
- Check measured resistance value for appropriate temperature range
using graph below (N24-0157).

Range A: 0 to 50 C

Range B: 50 to 100 C

Examples:
If resistance is NOT OK:
At 30 C, ECT sensor resistance should be 1500-2000 At 80 C, ECT sensor resistance should be 275-375
- Replace Engine Coolant Temperature (ECT) sensor -G62-.
- 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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24-71

- Compare displayed value with specified value
for intake air temperature (display field 4):

Display fields

1 2 3 4
Display group 4: Engine basic settings
Display xxx RPM xx.xxx V
xxx.x C
xxx.x C
Indicates Engine speed
(in 40 RPM
steps) Battery Positive
Voltage (B+) Engine coolant
temperature Intake air temperature
Range 0-6800 RPM 0.000-16.500 V -46.5 to 141.0 -46.5 to 141.0
Specified
value 0 RPM 10.000-14.500 V ---
approx. ambient temperature
1)

--- --- --- Continuation Page 24
-72
, Evaluation of
display group 4
1) If temperature displayed deviates significantly from ambient temperature, check sensor wiring for contact resistance or
open circuit.
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