warning light AUDI A4 1997 B5 / 1.G APB Engine Electronic Engine Power Control Checking Workshop Manual

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Significance of electronic Engine Power
Control (EPC) warning light in
instrument cluster

"EPC" stands for Electronic Power Control and
refers to the electronic throttle control system
(Drive by wire).

Component location of EPC warning light
The Engine Control Module (ECM) checks after the ignition has been
switched on all important parts of the electronic throttle control system for
functionality.
After the ignition is switched on the ECM turns on the EPC warning light.
Shortly after the engine has been started the EPC warning light goes out
if, no malfunctions regarding the electronic throttle control system are
stored in the ECM and if the activation for the EPC warning light is OK.
If a malfunction is detected in the electronic throttle system while the
engine is running, the ECM will activate the EPC warning lamp. At the
same time a Diagnostic Trouble Code (DTC) is stored in the DTC memory
of the Engine Control Module (ECM).
Checking function of warning light
- Switch ignition on.
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Specified value: The EPC warning light should
light up.
If the EPC warning light does not light up:

- Check wire from Engine Control Module (ECM)
to EPC warning light in instrument cluster as
follows: Cause:
EPC warning light is not activated or does
not light up because of an open circuit. Corrective action:
The EPC warning lamp should light up.
If the EPC warning lamp does not light up:
If the warning lamp and the voltage supply are OK: - Switch ignition off
- Connect VAG1598/31 test box . Do not connect engine control module.
- Bridge sockets 1 and 48 on test box
- Switch ignition on.
- Switch ignition off.
- Check whether lamp is burned out and test voltage supply to lamp wiring
diagram.
- Check for open circuit or short circuit in wiring between engine control module
and EPC warning lamp using wiring diagram. Determine and eliminate
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If EPC warning lamp remains lit for more than 3
seconds (i.e. continuously) when ignition is on,
proceed with test as follows:

- Start engine and allow it to run at idling speed.

Specified value: EPC warning lamp should go
out.
If the EPC warning lamp does not go out:

- Check DTC memory of Engine Control Module
(ECM).
If no DTCs are stored: Cause:
EPC warning light is activated via
short circuit to Ground (GND). Corrective action:
If the specification is not reached: - Switch ignition off
- Connect VAG1598/31 test box . Do not connect engine control module.
- Measure resistance between vehicle Ground and socket 48 on test box. Specified
value: infinity (because the wire should not have any direct Ground connection)
- Determine and eliminate short circuit to Ground in wiring between engine control
module and EPC warning lamp using wiring diagram.
If there are no malfunctions in the wiring to the EPC warning lamp:
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