With Manufacturer's Scan Tool

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
- 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. Test Box, Connecting For Wiring and Component Test
- 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 Measure to
Socket
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 Measure to
Socket
3 Engine
round (GND)

- Switch ignition on.

Specified value: approx. battery voltage (B+)

If specified values are not obtained:
- Check wiring connections.
- Connect multimeter as follows to measure voltage:

Test box V.A.G 1598/31 Measure to
Socket
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 15 minutes.

- Switch ignition on.

Specified value: approx. battery voltage (B+)

If specified value is not obtained:
- Check wiring connections.
- Check Motronic Engine Control Module (ECM) Power Supply Relay -J271-.