check engine AUDI A8 1998 D2 / 1.G AEB Engine EVAP System Checking

24-138

Voltage supply, checking

If LED tester does not light: - Disconnect harness connector for LDP -V144-.
- Connect VAG 1527B LED voltage tester between connector terminal 3
(B+) and engine Ground.
- Start engine and run engine at idle.
LED must light up.
- Check fuse for LDP -V144-.
- Check wiring for open circuit between terminal 3 and fuse, according to
wiring diagram. Specified value: max. 0.5 . - Check fuel pump relay and signal to relay Page 24
-81
.
Pa
ge 3 of 12 Eva
porative Emissions
(EVAP
) system, checkin
g
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.4

24-139

Evaporative Emission (EVAP) Canister
Purge Regulator Valve, checking


Required special tools and test equipment

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

Test conditions
Engine coolant temperature at least 80 C
(176 F)

Function check

- 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
Selectin
g 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-, -7- and -0- to input display group number 70, and
press -Q- button to confirm input.
Pa
ge 4 of 12 Eva
porative Emissions
(EVAP
) system, checkin
g
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.4

24-140

- Press -4- button- to select "Basic Setting"
function 04 (diagnosis for EVAP canister purge
regulator valve is initiated).

Note:
During this diagnosis there should not be any
load placed on the engine, otherwise the
diagnosis is interrupted and must be started
again. System in Basic Setting 70 1 2 3 4

Indicated on display (1-4 display fields)
If the diagnosis is initiated by the ECM, the display changes from "Test
OFF" to "Test ON" in display field 4.
Note:
If the display changes from "Test ON" to "Test OFF" during the test,
accelerate with a brief burst to repeat the test. - Continue to run engine at idle until "EVAP OK" is indicated in display
field 4.
Pa
ge 6 of 12 Eva
porative Emissions
(EVAP
) system, checkin
g
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.4

24-143

Checking EVAP canister purge regulator
valve voltage supply

Test conditions

Fuse for EVAP canister purge regulator
valve OK.

- Disconnect harness connector from EVAP
canister purge regulator valve.

If LED test light does not light:
If wiring is OK: - Connect VAG 1527B LED voltage tester between connector terminal 1
and engine Ground.
- Operate starter motor.
Specified value: LED must light up
- Check wiring for open circuit between connector terminal 1 and fuse,
according to wiring diagram. Repair if necessary.
- Check fuel pump relay Page 24
-81
.
Pa
ge 11 of 12 Eva
porative Emissions
(EVAP
) system, checkin
g
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.4