check engine AUDI A6 1999 C5 / 2.G ATQ Engine Motronic Injection System Servicing Owner's Manual

24-47

Checking Proper Seal

- Check proper seal of fuel injectors (visual
inspection). With Fuel Pump (FP) running, only 1
to 2 drops per minute may drip out per injector.

- If fuel loss is greater, stop Fuel Pump (FP) from
running (disconnect cable bridge) and replace
faulty fuel injector Page 24
-43
.

Checking Injection Quantity

- Insert fuel injector to be tested in a measuring glass from VAG1602
injection quantity test device.

- Connect one terminal of fuel injector to engine Ground (GND) using an
adapter cable and an alligator clip from VAG1594A connector test kit.
- Connect the second terminal of fuel injector to B+ using VAG1348/3A
remote control, VAG1348/3-2 adapter cable and assisting cable.
Pa
ge 56 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-51

Function test of Fuel Pump (FP) relay

- Remove driver-side storage compartment.

Repair Manual, Body
-Interior, Repair Group
68; Instrument Panel; Removing Driver
-Side
Storage Compartment


- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Ignition must remain switched on for this.

- Initiate output Diagnostic Test Mode Page 01
-
56
and activate Evaporative Emission (EVAP)
canister purge regulator valve -N80-.

A - If relay does not trigger:
Fuel Pump (FP) relay (at position 4 of central electrics in driver's
footwell, left) must trigger and Fuel Pump (FP) must run.
- Check voltage supply of Fuel Pump (FP) relay Page 24
-52
.
- Checking activation of Fuel Pump (FP) relay Page 24
-52
.Pa
ge 61 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-53


If relay triggers now, but didn't during output DTM:
If relay does not trigger:
Fuel Pump (FP) relay (at position 4 of central electrics in driver's
footwell, left) must trigger.
- Replace Engine Control Module (ECM) Page 24
-21
.
- Remove cable bridge.
- Remove Fuel Pump (FP) relay.

If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Connect multimeter to terminal 19 of relay socket and Ground (GND)
for voltage measurement.

Specification: approx. battery voltage
- Check wire connections.
Pa
ge 63 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-54
If specified value is obtained:

If no malfunctions are detected:
Check voltage supply for Fuel Pump (FP) and components - Check the following wire connection for open circuit and short circuit to
Ground (GND) and B+:
Central electric
in driver-side footwell, left, position 4
Terminal
VAG1598/31 test box


Socket
16 65
- Repair open circuit or short circuit if necessary.
- Replace Fuel Pump (FP) relay -J17-.
- Re-connect Engine Control Module (ECM).

- Remove fuses S228, S229, and S234 (positions 28, 29, and S234)
from fuse holder.
- Initiate output Diagnostic Test Mode Page 01
-56
and activate
Evaporative Emission (EVAP) canister purge regulator valve -N80-.
Pa
ge 64 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-57

Test requirements:

Coolant Temperature at least 80 C.

Electrical consumers switched off (radiator
fan must NOT run during test).
A/C switched off.
Fuse for Mass Air Flow (MAF) sensor OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

Checking function

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Engine must run at idle for this.Rapid data transfer
HELP
Select function XX

When indicated on display:
-
Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
Pa
ge 67 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-58

Basic Settin
g
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -0- and -2- to select "display group number 002" and press -Q-
button to confirm input.
System in Basic Setting 2
1
2
3
4

When indicated on display:
- Check specified values for load detection in display fields 3 and 4.

Display fields

1 2 3 4
Display group 002: Air mass taken in with engine at idle and operating temperature
Display xxx /min xx.x %
x.x ms
xxx.x g/s
Indicated Engine speed
(RPM) Load
mean injection time
Air mass
Functional
range 630 to 6800
RPM 12 to 100
% 1.0 to 20.0 ms
1.0 to 150 g/s
Specified
value 720 to 820
RPM
1)
630 to 730
RPM2) 12.0 to
26.0 % 1.0 to 4.0 ms
1.0 to 5.0 g/s
Notes --- ---
If specified value is not obtained:
Evaluation display field 3 Page 24
-
59

If specified value is not obtained:
Evaluation display field 4 Page 24
-
60

1) Front Wheel Drive Vehicles
Pa
ge 69 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-59
If specified values are obtained:

-
Press button.Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
Evaluation display group 002
Display field: 3
Possible cause
Corrective action
less than 1.0
ms
Smaller values are only possible when driving in
deceleration mode
larger than 4.0
ms Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Poor idle (does not run on all cylinders)- Check spark plugs.
- Check fuel injectors Page 24
-36


Throttle valve control module - J338- faulty- Check throttle valve control module Page
24
-141

Pa
ge 71 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-60
Evaluation display group 002 Display field:
4
Possible cause
Corrective action
smaller than
1.0 g/s
large false air mass between intake manifold and Mass Air
Flow (MAF) sensor
Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check intake system for leaks (false
air) Page 24
-64

- Check voltage supply Page 24
-61
larger than 5.0
g/s
Engine under load due to power accessories.- Reduce load (A/C system/power
steering/generator)

Voltage supply of Mass Air Flow (MAF) sensor or wire
connections to Engine Control Module (ECM) - Check voltage supply Page 24
-61
Pa
ge 72 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-61

Voltage supply for Mass Air Flow (MAF)
sensor, checking

- Disconnect connector from Mass Air Flow (MAF)
sensor.

Note:
Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP)
relay.
If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
3 Engine Ground (GND)
- Operate starter briefly.

Specification: approx. battery voltage
- Check wire connection from terminal 3 of connector to Fuel Pump (FP)
relay via fuse for open circuit and short circuit to Ground (GND):
Pa
ge 73 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1

24-64

Intake air system, checking for leaks
(unmetered air)


Special tools and equipment

Notes:
VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3BEngine leak detection spray G 001 800 A1The negative pressure in the intake system sucks in the leak detection
spray with the unmetered air. Leak detection spray decreases ignition
quality and performance of the fuel mixture. This causes a reduction in
engine speed and a sharp increase of CO content. It is absolutely necessary to follow the safety precautions listed on the
can.
Pa
ge 76 of 78 Motronic in
jection s
ystem, servicin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.1