Engine Control Module (ECM) power supply, checking
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 .