The ecu controls the IC pump on our trucks. The stock ecm turns the pump on
based on engine coolant temperatures. To aid in cooling and prevent the IC from
heating up during warm up, we hard wire the IC pump on.
So with this mod, when the truck is in the on position, the pump runs. This
is ideal for stock chipped trucks, and essential for stock chipped trucks with
a lower temperature thermostat.
Hot wiring the pump
First step is to orient yourself with what controls the pump. There is a fuse
in a fuse holder behind the alternator that is for the IC.
The pump is powered by one of the relays on the fire wall. The two closest to
the power block(passenger side) are the fuel pump relay and the IC pump relay.
The right most of the two is the IC pump. Its the only one with a yellow wire.
There are two methods to hot wiring the pump. You can splice/tap the yellow
wire, and run to a ground.
The other option is to dismantle the relay, and wind a wire around the relay
tab to avoid any permanent cuts to the harness.
The relay is easily removable, remove the two bolts holding the metal bracket
to the firewall.
On the back, the metal bracket has a clip you need to pry up, and slide the
relay off the top of the bracket.
The relay then can be separated easily from the bottom plug.
If you fold the new wire to be grounded over the "tab" on the relay itself (corresponding
to the yellow wire).
Intrusive (cut cut)
Removing the bracket will aid in installing a tap, sometimes it is difficult
with the space limitations.
You can use a "scotch lock" or wire tap to simply piggy back into the wire and
run to ground.
The grounded wire can be simply connected to one of the screws holding various
things onto the firewall (except of course the power block).
Or, you can run the wire to a switch with 2 polls, one going to the yellow wire,
the other going to a ground.
Test your work, and if you have problems, look for the article about diagnosing
IC pump problems.