A8 Quattro Sedan V8-4.2L (BVJ) (2008)
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Check the wiring connection for damage, corrosion, lose or broken terminals.
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If necessary, repair the faulty wiring connection.
If the specified value was obtained:
Checking activation
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Switch the ignition on.
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Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to Ground (GND).
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Switch the ignition off.
Specified value: 0.5 V Max.
If the specified value was obtained:
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Replace the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
If the specified value was not obtained:
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Check the wiring from the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to the Motronic Engine Control
Module (ECM) (J623) electrical harness connector T94 terminal 69 for a short to Ground (GND) or an open circuit.
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If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring and voltage supply was not OK:
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Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Removing and Installing ] See: Service and
Repair.
Checking voltage
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Switch the ignition on.
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Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 2/87 to Ground (GND) for voltage.
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Switch the ignition off.
Specified value: battery voltage.
If the specified value was not obtained:
Checking wiring
If the manufacturers test box is being used. Perform the following step.
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Install the test box.
If the manufacturers test box is not being used. Perform the following step.
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Remove the Motronic Engine Control Module (ECM) (J623) or the. Refer to => [ Engine Control Module, Removing and Installing ] See: Service
and Repair.
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Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 2/87 to the Motronic Engine Control
Module (ECM) (J623) electrical harness connector T94 terminals or the electrical harness connector T94 terminals for resistance.