Checking fuel pump control unit J538 - vehicles with FSI engine — AUDI

Checking
fuel pump control unit
J538
- vehicles with FSI engine
Special tools and workshop equipment required
Hand-held multimeter
V.A.G 1526C
Auxiliary measuring set
V.A.G 1594C
Adapter cable
V.A.G 1598/39
Test box
V.A.G 1598/42
Procedure
Observe test conditions
Chapter
.
Checking voltage supply for fuel pump (from
fuel pump control unit
J538
)
If necessary, fold forward backrests of rear seat bench.
Saloon:
Take out luggage compartment floor trim.
Avant:
Remove luggage compartment load surface
1
.
Note
Disregard
item 2
.
On vehicles without air suspension: unclip the retaining tabs
arrows
for the flange cover.
On vehicles with air suspension: remove spreader pins
arrows
and take off cover
1
.
All vehicles:
On vehicles with air suspension: unscrew bolts
arrows
.
Detach accumulator
2
and lay it aside with line
1
connected.
Note
Do not stretch or kink line.
Saloon:
Note
It is advisable to carry out work on the flange from the vehicle interior with the rear seat backrest folded down, therefore the following illustrations are shown from this perspective.
Release retaining lugs
arrows
.
Fold retaining lugs
1
and
3
open to rear.
Fold cover
2
to front
arrow
.
All vehicles:
Unscrew cover for flange
arrows
.
Connect
hand-held multimeter
V.A.G 1526C
for voltage measurement with measuring probes and plug-in adapters from
adapter set
V.A.G 1594C
between contacts
1
and
5
, as shown in illustration; the electrical connector remains in place.
Note
The connector contacts are numbered accordingly on the back of the connector.
Start engine.
Specification when starting and at idling speed: approx. 4 ... 5 V.
Press accelerator pedal quickly to the floor and release again (short throttle burst).
Specification: The voltage value should first increase slightly, then drop and eventually rise to the previous reading.
If display differs from specification described above:
Check voltage supply and activation of fuel pump control unit
J538
.
Checking voltage supply for
fuel pump control unit
J538
Unplug electrical connector
arrow
on
fuel pump control unit
J538
.
Connect multimeter between contacts
3
and
4
of connector to measure voltage.
Switch on ignition.
Specification: approx. battery voltage
If specification is not obtained:
Eliminate open circuit in wiring (refer to current flow diagram).
Checking activation of fuel pump control unit
J538
Connect multimeter for voltage measurement with measuring probes and plug-in adapters from
auxiliary measuring set
V.A.G 1594C
between contacts
4
and
5
, as shown in illustration; the electrical connector remains in place.
Note
The connector contacts are numbered accordingly on the back of the connector.
Start engine.
Specification when starting and at idling speed: approx. 5.0 V.
Press accelerator pedal quickly to the floor and release again (short throttle burst).
Specification: The voltage value should first increase slightly, then drop and eventually rise to the previous reading.
If display differs from specification described above:
Switch off ignition.
Connect the
test box
V.A.G 1598/42
to wiring harness with adapter lead
V.A.G 1598/39-1
or adapter lead
V.A.G 1598/39-2
. Do not connect engine control unit. Connect earth clip of test box to negative terminal of battery
Rep. Gr.
24
.
Caution
Electronic components are susceptible to damage.
Select the appropriate measuring range before connecting the test leads and observe test requirements.
Check for open circuit and short to positive or earth in the following wiring:
Connector
Contact
V.A.G 1598/42
Socket
5
4-cyl. TFSI: B 27
6-cyl. FSI: B 35
Repair open circuit or short circuit in wiring (refer to current flow diagram).
If no fault is found:
Renew
fuel pump control unit
J538
.
Install accumulator
Rep. Gr.
43
.