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→ Location of the EPC warning lamp
When the ignition is switched on, the engine control unit checks all the components of importance to the electronic throttle system.
After switching on the ignition the engine control unit switches on the EPC warning lamp. The EPC lamp goes out shortly after starting the engine, if, on the one hand, the engine control unit does not detect any faults in the EPC system, and, on the other, if actuation of the lamp by the engine control unit is OK.
If a fault is detected in the electronic throttle system while the engine is running, the engine control unit switches on the EPC warning lamp. At the same time, an entry is made in the engine control unit fault memory.
Functional test of warning lamp (this test does not apply to vehicles which fulfil emission standard EU-III, since the EPC warning lamp is switched on via the CAN data bus in EU-III vehicles).
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‒ Switch the ignition on.
Specification: EPC warning lamp should light up.
If the EPC warning lamp does not come on:
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‒ Check the line from the engine control unit to the EPC warning lamp as follows:
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Cause
EPC warning lamp has not been activated or is not lit because of an open circuit.
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Remedy:
-Switch off ignition.
-Connect test box V.A.G 1598/31; do not connect engine control unit.
-Bridge sockets 1 and 48 on test box.
-Switch on ignition.
EPC warning lamp should come on.If the EPC warning lamp does not come on:
-Switch off ignition.
-Find and rectify short circuit or open circuit between engine control unit and EPC warning lamp with the aid of current flow diagram.
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If no fault is found in line to EPC warning lamp:
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Cause of fault
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Instrument cluster defective => renew instrument cluster
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‒ Start engine and run at idling speed.
Specification: EPC warning lamp should go out shortly after starting.
If the EPC warning lamp does not go out:
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‒ Interrogate the fault memory of the engine control unit.
If no fault is stored:
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Cause
EPC warning lamp is continuously activated by short to earth.
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Remedy:
-Switch off ignition.
-Connect test box V.A.G 1598/31; do not connect engine control unit.
-Measure resistance between vehicle earth and socket 48 in test box. Specification: infinite resistance (because this line should have no direct connection to earth).
If specification is not attained:
-Find and rectify short circuit to earth in line between engine control unit and EPC warning lamp with the aid of current flow diagram.
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If no fault is found in line to EPC warning lamp:
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Cause of fault
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Instrument cluster defective => renew instrument cluster
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