Motronic Engine Control Module (ECM) power supply, checking
Special tools and workshop equipment required
- V.A.G 1526 A Multimeter
- V.A.G 1594 A Connector test kit
- V.A.G 1598/31 Test box
Requirements
- Fuses for engine electronics OK
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Battery voltage at least 12.7 V
- Generator OK
Work sequence
- Connect test box V.A.G 1598/31 to wiring harness for ECM; do not connect directly to ECM. Refer to Electrical testing using VAG1598/31 test box .
- Switch ignition on.
NOTE:
- The positive voltage supply to the ECM is provided via terminal 3 (terminal 15) and terminal 62 (terminal 30).
- The ground (GND) connection to the ECM is provided via terminal 1 and terminal 2.
- Connect multimeter as follows to measure voltage:
| Test box V.A.G 1598/31 Socket |
Measure to |
| 1 | Battery positive (B+) |
| 2 | Battery positive (B+) |
| 62 | Engine Ground (GND) |
- Specified value: approx. battery voltage (B+)
- Connect multimeter as follows to measure voltage:
| Test box V.A.G 1598/31 Socket |
Measure to |
| 3 | Engine Ground (GND) |
- Switch ignition on.
- Specified value: approx. battery voltage (B+)
If 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 V.A.G 1598/31 Socket |
Measure to |
| 121 1) | Engine Ground (GND) |
1) The Motronic Engine Control Module (ECM) Power Supply Relay -J271- carries voltage on terminal 121 of ECM after switching off the ignition for up to 15minutes.
- Switch ignition on.
- Specified value: approx. battery voltage (B+)
If specified value is not obtained:
- Check wiring connections.
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations
- Check Motronic Engine Control Module (ECM) Power Supply Relay -J271-. Refer to Motronic ECM Power supply relay -J271-, checking .