Volkswagen Golf / Golf GTI / Jetta. Manual — part 86

20-64

Electronic Power Control
(EPC)

Function of EPC systems

With the EPC system the throttle valve is not

operated by the throttle pedal via a cable.
There is no mechanical connection between
accelerator and throttle valve.

The position of the accelerator is transmitted

to the engine control module by two sensors
(variable resistors; mounted in one housing)
which are connected to the accelerator
pedal.

The position of the accelerator (drivers

requirement) is the main input value for the
engine control module.

An electric motor (throttle actuator) in the

Throttle valve control module -J338-
actuates the throttle valve over the entire
range of engine speeds and load.

The throttle valve is operated by the throttle

actuator under instructions from the engine
control module.

When the engine is not running and the

ignition is switched on the engine control
module moves the throttle valve exactly as
prescribed by the accelerator pedal position
sender. This means that when the
accelerator is depressed halfway the throttle
valve positioner opens the throttle valve by
the same amount, the throttle is then
approximately half open.

Electronic Power Control (EPC)

20-65

When the engine is running (under load) the

engine control module can open or close the
throttle valve independently of the
accelerator pedal position sender.

This means that the throttle valve can

already be completely open even though the
accelerator pedal is depressed half way.
This has the advantage of preventing
throttle losses at the throttle valve.

This also gives vastly improved fuel

consumption and exhaust emission levels at
certain load conditions.

It is wrong to believe that EPC only consists

of two components. It is a system which
contains all components needed to help
determine, regulate, and supervise the
throttle valve position (e.g. the throttle
position sensor which measures the
accelerator position, the throttle valve
control module, the EPC indicator lamp, the
engine control module).

Electronic Power Control (EPC)

20-66

Electronic
Power
Control
(EPC),
servicing

Repair

1 - Mounting

bracket

2 - Connector

Black,

6-pin

Gold

plated
contacts

3 - 10 Nm

4 - Throttle

Position
(TP)
sensor -
G79-

Not

adjustable

TP sensor

passes
driver's
requirements
on to engine
control
module

Remove

footwell
cover to
remove
sensor

Checking

Page

20-67

If replaced

adapt control
module for
automatic
transmission:

Electronic Power Control (EPC)

Manual, 5 Spd.
Automatic
Transmission
09A On Board
Diagnostic
(OBD); Repair
Group 01

5 - Bracket

For

footwell
cover

Clipped

onto
accelerator
pedal

Electronic Power Control (EPC)