Engine Control Module Power Supply, Checking

Engine Control Module Power Supply, Checking





Special tools, testers and auxiliary items required

• Multimeter (V.A.G 1526 A)

• Connector test kit (V.A.G 1594 A)

• Test box (VAG1598/31)

Requirements

• Fuses for engine electronics OK

• Battery voltage at least 12.7 V

• Generator OK

Work sequence

- Connect test box (VAG1598/31) to wiring harness for ECM; do not connect directly to ECM => [ Electrical Testing, with Test Box VAG 1598/31 ] Electrical Testing, With Test Box VAG 1598/31.

- Switch ignition on.

• 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:





• Specified value: approx. battery voltage (B+)

- Connect multimeter as follows to measure voltage:





- 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:





* 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) => [ ECM Power Supply Relay, Checking ] ECM Power Supply Relay, Checking.