Resistance Ladder
Resistance Ladder Circuit
6
5
4
3
2
E88295
1
1
Description
Item
To Green/White Wire
1
Stop Engine
2
RPM 1 on/off or Variable Control 'Idle'
3
RPM 2 on/off or Variable Control 'Negative (-)'
4
RPM 3 on/off or Variable Control 'Positive (+)'
5
RPM Control Armed or Increased Idle on/off
6
The resistance ladder circuit acts as a potential
divider. The PCM has an internal reference voltage
of 5 volts. Current passes through an internal 320
ohm resistor (not shown above) prior to passing
through the resistance ladder. There is also a
(second) 220 nF capacitor internally within the
PCM between the 320 ohm resistor and ground
(not shown above) and this is to reduce
Electromagnetic Compatibility (EMC) effects.
With all the switches open there is a total
resistance in the green/white loop of approx 4310
ohms and this corresponds to normal driving
operation (the condition prior to the loop being
cut).
To ensure robust operation, it is recommended
for all switches that a switch de-bounce
specification is chosen as close to zero ms (mili
seconds) as possible.
Starting from the right of the diagram, when the
key switch is closed only 2110 ohms is in the circuit
and the PCM software recognizes this as the RPM
mode being armed and ready for operation (Key
switch closed = off, open = on.
Note:
this is the
reverse situation of vehicles with 2.2L engine). A
key switch is recommended in this position for a
couple of reasons:
•
If the control box is located externally on the
vehicle, the requirement for a key avoids any
passers by being able to put the vehicle into
RPM Speed Control mode by simply pressing
a button.
•
Using a key switch where the key can be
removed in either the on or off condition could
be used as an aid to anti-theft. If the operator
uses a key to put the vehicle into RPM Speed
control mode and then removes the key, then
the vehicle cannot quickly and easily be taken
out of RPM speed control mode. If a foot pedal
is pressed while in either the 3 speed or variable
speed modes, the vehicles engine will stall and
therefore the vehicle cannot easily be driven
away and stolen. A software update is
available from November 2016 which will
prevent the engine from starting after a stall
event until the RPM speed control box is turned
off. Check with your local Ford dealer or NSC
for latest software update.
When in 3 speed mode pressing any of the middle
3 switches (with the feature armed) results in the
engine RPM jumping to the corresponding RPM
value held in memory (defaults of 1100, 1600 or
2030rpm) for the 3 switch positions. A second
consecutive press of the same button returns to
normal idle.
Date of Publication: 03/2018
FORD
TRANSIT
2016.75
4 El
ec
tric
al
153
EU
