Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI199590 QUATTRO SPORT V6-2.8L (AAH)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONSCAN TOOL TESTING AND PROCEDURESSCAN TOOL TESTINGSCAN TOOL CONNECTING AND INITIAL CHECKSCONNECTING VAG 1598/31 TEST BOX
1995 Audi 90 Quattro Sport V6-2.8L (AAH)
Connecting VAG 1598/31 Test Box
1995 Audi 90 Quattro Sport V6-2.8L (AAH)SECTION Connecting VAG 1598/31 Test Box
DESCRIPTION
A Pin Out Box must be used when making electrical checks at the ECM connectors to avoid damaging the connectors.
The VAG 1598 Test Box is a Pin Out box manufactured for and sold by Audi.
The Audi test procedures refer to its use specifically, along with the following; VW 1594 Test connector kit, VAG 1527B or US 1115 LED tester or equivalent and a Digital Volt/Ohm Meter (DVOM). Refer to Tools and Equipment for test equipment specifications.
NOTE: There are Pin Out boxes other than the VAG 1598 that are available from other manufacturers that will work for these tests. If using a different pin out box verify the correct pin connections with the pin out box manufactures instructions.
VAG 1598 TEST BOX CONNECTIONS

The socket numbers on the VAG 1598, in conjunction with adapter harness VAG 1598/11, correspond to the Engine Control Module (ECM) connectors as shown in the chart.
Use the VW 1594 adaptor kit to make connections between the Test Box, LED tester and DVOM.
The values given are valid within an ambient temperature range of 0°C to 40°C (32°F to 104°F)
NOTES:
If measured values differ from the specifications, check the wiring to the component using the wiring diagram before replacing the component, especially for values specified at less than 10 Ohms in which case the resistance measurement for the component should be repeated at the component.
If a measured value only deviates slightly from the specified value, clean the tester terminals, connectors and measuring wires and then repeat the test.
CAUTION: Switch multimeter to the appropriate measuring range BEFORE connecting the test leads to avoid damaging sensitive electronic components.
REQUIREMENTS FOR ELECTRICAL TESTS
- Battery voltage OK
- Fuses OK
- Ground connections OK
- Fuel pump and fuel pump relay OK
PIN OUT BOX CONNECTION PROCEDURE
CAUTION:
DO NOT have the VAG 1598 Test Box connected at the same time as the VAG Scan Tool.
Wait 30 seconds after switching OFF the ignition BEFORE disconnecting the ECM harness connector to allow the hot wire in the Mass Air Flow sensor to heat up and self clean.
Disconnecting the ECM harness connector removes power from the Diagnostic Trouble Code (DTC) Memory thus erasing any contents.
- Switch OFF ignition
- Remove ECM.
- Disconnect harness connectors from the ECM.
- Connect adaptor cable VAG 1598/11 between the Test Box and engine control module harness connectors.
- The ECM is left disconnected.
NOTE: Vehicles with automatic transmissions:
Performing electrical checks will generate and store malfunctions in the DTC memory for the Transmission Control Module (TCM) which must be erased. Refer to On-Board Diagnostics.
- Perform the electrical checks described at each component test procedure.
A Pin Out Box must be used when making electrical checks at the ECM connectors to avoid damaging the connectors.
The VAG 1598 Test Box is a Pin Out box manufactured for and sold by Audi.
The Audi test procedures refer to its use specifically, along with the following; VW 1594 Test connector kit, VAG 1527B or US 1115 LED tester or equivalent and a Digital Volt/Ohm Meter (DVOM). Refer to Tools and Equipment for test equipment specifications.
NOTE: There are Pin Out boxes other than the VAG 1598 that are available from other manufacturers that will work for these tests. If using a different pin out box verify the correct pin connections with the pin out box manufactures instructions.
VAG 1598 TEST BOX CONNECTIONS
Conversion Chart, ECM To VAG 1598 Tester:
The socket numbers on the VAG 1598, in conjunction with adapter harness VAG 1598/11, correspond to the Engine Control Module (ECM) connectors as shown in the chart.
Use the VW 1594 adaptor kit to make connections between the Test Box, LED tester and DVOM.
The values given are valid within an ambient temperature range of 0°C to 40°C (32°F to 104°F)
NOTES:
If measured values differ from the specifications, check the wiring to the component using the wiring diagram before replacing the component, especially for values specified at less than 10 Ohms in which case the resistance measurement for the component should be repeated at the component.
If a measured value only deviates slightly from the specified value, clean the tester terminals, connectors and measuring wires and then repeat the test.
CAUTION: Switch multimeter to the appropriate measuring range BEFORE connecting the test leads to avoid damaging sensitive electronic components.
REQUIREMENTS FOR ELECTRICAL TESTS
- Battery voltage OK
- Fuses OK
- Ground connections OK
- Fuel pump and fuel pump relay OK
PIN OUT BOX CONNECTION PROCEDURE
CAUTION:
DO NOT have the VAG 1598 Test Box connected at the same time as the VAG Scan Tool.
Wait 30 seconds after switching OFF the ignition BEFORE disconnecting the ECM harness connector to allow the hot wire in the Mass Air Flow sensor to heat up and self clean.
Disconnecting the ECM harness connector removes power from the Diagnostic Trouble Code (DTC) Memory thus erasing any contents.
- Switch OFF ignition
- Remove ECM.
- Disconnect harness connectors from the ECM.
- Connect adaptor cable VAG 1598/11 between the Test Box and engine control module harness connectors.
- The ECM is left disconnected.
NOTE: Vehicles with automatic transmissions:
Performing electrical checks will generate and store malfunctions in the DTC memory for the Transmission Control Module (TCM) which must be erased. Refer to On-Board Diagnostics.
- Perform the electrical checks described at each component test procedure.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.