Motronic 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 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 .