Checking power supply to diesel direct-injection system — AUDI
Checking power supply to diesel direct-injection system on Audi: factory workshop procedure for engines AFF, AFN, AGR, AHF.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
📋 Procedure
AFN AHH AHU
The injection system receives its current supply via the diesel direct injection system relay (J322).
Precondition for the closing of the relay (J322) is the application of voltage via terminal 15 at the control device for the diesel direct-injection system. This means that the relay (J322) is only earthed (via the control device for the diesel direct-injection system), if the control unit receives voltage via terminal 15.
Test conditions
Battery voltage OK.
Testing voltage supply at terminal 15
Connect test box V.A.G 1598/22 to wiring harness for engine control unit =>Page
23-46
.
Connect multimeter between earth and socket 47 of the test box to measure the voltage.
Switch the ignition on.
Specified value: approx. battery voltage
If specified value is not attained:
Check the wiring connections.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
Testing earth actuation for Diesel direct injection system relay -J322
Test conditions
Battery voltage OK.
Terminal 15 power supply OK
Open electronics box in plenum chamber.
Switch the ignition on.
Specified value: Diesel direct-injection system relay (electronics box, relay position 3) must be energised.
Note:
The clicking of the valve is difficult to hear and is therefore best checked by touching the relay.
If the relay does not respond:
Connect test box V.A.G 1598/22 to wiring harness for engine control unit =>Page
23-46
.
Connect together sockets 33 and 1 on the test box using an auxiliary cable from V.A.G 1594.
Specified value: Diesel direct-injection system relay (electronics box, relay position 3) must be energised.
If the relay picks up now, but not when the control unit is connected:
Renew Diesel direct-injection system control unit.
If the relay does not respond:
Switch ignition off.
Unplug J322 diesel direct-injection system relay from relay panel (electronics box, relay position 3).
The following wiring connections are to be checked for open circuits and/or short to positive or negative.
Electronics box, relay panel 3, contact · Test box V.A.G 1598/22, socket
9 · 33
Rectify any open/short circuit as necessary.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
Testing voltage supply at terminal 30
Test conditions
Battery voltage OK.
Terminal 15 power supply OK
Earth actuation for relay J322 OK
Switch ignition off.
Unplug -J322 diesel direct-injection system relay from relay panel (electronics box, relay position 3).
Connect multimeter (voltage test range) between the following contacts on the relay panel:
Electronics box, relay panel 3, contact · Specified value
2 + earth · approx. battery voltage
If specified value is not attained:
Check the wiring connections.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
If specified value is attained:
Plug the relay back into the relay panel (electronics box, relay position 3).
Connect test box V.A.G 1598/22 to wiring harness for engine control unit =>Page
23-46
.
Connect together sockets 33 and 1 on the test box using an auxiliary cable from V.A.G 1594.
Connect multimeter between the following contacts on the test box to test the voltage:
Test box V.A.G 1598/22, socket · Specified value
2 + 1 · approx. battery voltage
28 + 1 · approx. battery voltage
2 + 27 · approx. battery voltage
28 + 27 · approx. battery voltage
If specified value is not attained:
Check the wiring connections.
=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
TorqFix answers live for your specific car — tell it the engine code and it serves the matching sequence, torque figures and wiring for that exact variant.
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.