imsolidstate

Fast idle mod

I found this write up by Skweeker at powerstroke.org for adding a fast idle or high idle switch to your pre-’05 6.0l. It takes advantage of the PTO capability that is programmed into the engine computer, even if you don’t have a PTO. Takes only a few minutes, and works great. Note that this write-up is specifically for 2004 with automatic.

“Here’s what you need to do. Look up under the dash between the steering column and the parking brake pedal. You will find a wiring harness behind the parking brake handle with a bunch of wires coming out of the harness that have the ends sealed off with charcoal?? colored heat shrink tubing.
If your not sure what you are looking at, look at the three wiring harnesses that come through the firewall to the left of the steering column shaft into the passenger compartment. The top harness is big, the middle harness is smaller than the top harness and the last harness closest to the floor is smaller still. The wire you are looking for comes out of the the middle harness where the harness routes up to the dash directly behind the parking brake handle.
One of these wires will be Light Blue with a Yellow stripe. This is the PTO function wire from the PCM. Placing battery power (battery positive) on this wire will command the PCM to raise the idle speed to 1200rpm as long as the transmission is in Park or Neutral and the service brake is released, meaning your foot is not on the brake pedal and the brake lights are not activated.
The other wire you are looking for is a White wire with a Light Blue stripe. This one is also easy to find. While looking under the dash direct your attention to the black OBD II datalink connector mounted to the lower part of the dash to the right of the steering column. This connector is what a service tech uses to hook up a scan tool which is needed to communicate with the vehicle PCM in order to check engine sensor data, engine trouble codes and to REFLASH your PCM. (You’ve heard about FLASHES haven’t you???)
Anyway, look at this black connector and follow the wiring harness from the plug back up and inside the dash. Along the harness not too far up from the plug you will find the White wire with a Light Blue stripe included in the bundle of wires but the wire just stops short of the connector. Yes the wire does not plug into any one of the ports of the datalink connector.
This White wire with a Light Blue stipe is your positive battery source wire that you will connect to the Light Blue with a Yellow stripe PTO wire through a switch.”

I installed a rocker switch on the panel just below and to the right of the headlight switch. The plastic is really soft, so it cuts easily with a hobby knife. Plus, the fuse panel drops out right underneath which makes wiring everything up really easy.

Tags: 6.0, Fast Idle, High Idle, Powerstroke