Audi Workshop Service and Repair Manuals

Checking Motronic current supply relay -J271- Special tools and workshop equipment required t  Portable multimeter -V.A.G 1526C- t  Adapter set -V.A.G 1594C- t  121-pin adapter cable -V.A.G 1598/31-

Test sequence   Note The Motronic current supply relay -J271- provides voltage for the ignition coils/output stages and the engine control unit at pin 121.

–  Remove the engine cover -arrows-.

–  Unplug the 4-pin connector -1- at one of the ignition coils -2-.

–  Connect up the multimeter (voltage measuring range) as follows.

Connector Contact	Measure to
1	Engine earth

–  Switch on ignition. t  Specification: approx. battery voltage If the reading does not match the specification: –  Switch off ignition.

–  Detach the current supply relay -1- beneath the cover on the left at the bulkhead.

–  Use the current flow diagram to check for open circuit in the following connection:

Relay carrier beneath cover on left at bulkhead Contact	Connector at ignition coils Contact
2	1

–  Eliminate open circuit in wiring if necessary. If the wiring is OK: –  Check voltage supply of Motronic current supply relay -J271-. Checking voltage supply –  Switch off ignition.

–  Detach the current supply relay -1- beneath the cover on the left at the bulkhead.

–  Connect up the multimeter (voltage measuring range) as follows.

Relay carrier beneath cover on left at bulkhead Contact	Measure to
1	Engine earth
3	Engine earth

t  Specification: approx. battery voltage If the reading does not match the specification: –  Perform the following checks marked with a dot:

l  Check fuse S10 (in fuse carrier, position 10).

l  Check fuse S134 (110 A) in main fuse box/battery. l  Check for open circuit in the wiring from battery + (terminal 30) via fuse S134 and fuse 10 to the Motronic current supply relay -J271- (beneath cover on left at bulkhead). → Current flow diagrams, Electrical fault finding and Fitting locations l  Check activation of Motronic current supply relay -J271-. Checking activation –  Switch off ignition.

–  Detach the current supply relay -1- beneath the cover on the left at the bulkhead.

–  Connect up the multimeter (voltage measuring range) as follows.

Relay carrier beneath cover on left at bulkhead Contact	Measure to
5	Battery positive

–  Switch on ignition. t  Specification: approx. battery voltage If the reading does not match the specification: –  Switch off ignition. –  Connect the test box -V.A.G 1598/31- to the wiring harness to the engine control unit, but do not connect the actual engine control unit → Chapter.

–  Check for open circuit and short to earth or positive in the following wiring:

Relay carrier beneath cover on left at bulkhead Contact	Test box -V.A.G 1598/31- Socket
5	21

–  Eliminate open circuit in wiring/short circuit if necessary. If no fault is found: –  Renew Motronic current supply relay -J271-.