A8 Quattro Sedan V8-4.2L (BVJ) (2008)
/Page-180001.png)
Engine Control Module: Testing and Inspection
Voltage Supply of Engine Control Module (ECM), Checking
Voltage Supply, Checking
The Motronic Engine Control Module (ECM) Power Supply Relay (J271) supplies voltage to the Motronic Engine Control Module (ECM) (J623).
Special tools, testers and auxiliary items required
‹› Multimeter.
‹› Wiring diagram.
Test requirements
‹› fuse (S133) OK.
‹› fuse (SC21) OK.
‹› fuse (SC6) OK.
‹› Battery voltage at least 12.5 volts.
‹› All electrical consumers such as, lights and rear window defroster, switched off.
‹› Vehicles with automatic transmission, selector lever in position " P" or "N".
‹› A/C switched off.
‹› Ground (GND) connections between engine/transmission/chassis OK.
‹› Ignition switched off.
Test sequence
-
Remove the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
Checking voltage
-
Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 1/30 to Ground (GND).
Specified value: battery voltage.
If the specified value was not obtained:
-
Check the wiring connections from the Battery to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 1/30 for an
open or short circuit.
-
Check the wiring connections for damage, corrosion, lose or broken terminals.
-
If necessary, repair the faulty wiring connection.
If the specified value was obtained:
-
Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket3/86 to Ground (GND).
-
Switch the ignition off.
Specified value: battery voltage.
If the specified value was not obtained:
-
Check the wiring connections from the Battery to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 3/86 for an
open or short circuit.
