Engine Control Module (ECM) power supply, checking
WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Special tools and equipment
- VAG1526 A
- VAG1594 A
- VAG1598/31
Test requirements
- Fuses for engine electronics OK
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Battery voltage at least 12.7 V
- Alternator OK
Test sequence
- Connect test box VAG1598/31 to wiring harness for engine control module; do not connect engine control module. Refer to Wiring and component check with test box VAG 1598/31 .
- Switch ignition on.
NOTE:
- The positive voltage supply to the engine control module is provided via terminal 3 (terminal 15) and terminal 62 (terminal 30).
- The ground connection to the engine control module is provided via terminal 1 and terminal 2.
- Connect multimeter as follows to measure voltage:
| Test box VAG1598/31 Socket |
Measure to |
| 1 | Battery positive |
| 2 | Battery positive |
| 62 | Engine ground |
- Specified value: approx. battery voltage
- Connect multimeter as follows to measure voltage:
| Test box VAG1598/31 Socket |
Measure to |
| 3 | Engine ground |
- Switch ignition on.
- Specified value: approx. battery voltage
If the specified values are not obtained:
- Check wiring connections.
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Connect multimeter as follows to measure voltage:
| Test box VAG1598/31 Socket |
Measure to |
| 121 1) | Engine ground |
1) The Motronic Engine Control Module (ECM) power supply relay -J271- carries voltage on terminal 121 of engine control modules after switching off the ignition for up to 15 minutes.
- Switch ignition on.
- Specified value: approx. battery voltage
If specified value is not attained:
- Check wiring connections.
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Check Motronic Engine Control Module (ECM) power supply relay -J271-. Refer to Motronic Engine Control Module (ECM) power supply relay -J271-, checking .