A4 Quattro Cabriolet L4-2.0L Turbo (BWT) (2009)
Main Relay (Computer/Fuel System): Testing and Inspection
Engine Control Module Power Supply Relay, Checking
Engine Control Module Power Supply Relay, Checking
Special tools, testers and auxiliary items required
‹› Multimeter.
‹› Wiring diagram.
Test requirements
‹› Fuse Strip (S88) 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 procedure
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Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] See: Computers and Control Systems/Testing
and Inspection/Initial Inspection and Diagnostic Overview/General Diagnosis.
Start diagnosis
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Using a Multimeter, check the following wiring connections for voltage.
Specified value: 12.5 V
If the specified value was not obtained:
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Check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 1/30 and 3/T to the Battery (A) (+) terminal for an open
circuit or short to Ground (GND).
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Check the electrical harness connectors for damage, corrosion, loose or broken terminals.
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If necessary, repair the wiring connection.
If no malfunctions are found in the wiring:
Checking Ground (GND)
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Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 4/86 to the Engine Control Module
(ECM) (J623) electrical harness connector terminal T94/69 for resistance.
Specified value: 1.5 ohms.
If the specified value was not obtained:
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Check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 4/86 to the Engine Control Module (ECM) (J623)
electrical harness connector terminal T94/69 for an open circuit or a short to Battery (+) or to Ground (GND).