Fast Idle Speed on a 6.5 Turbo Hummer

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Use this info to get a fast idle speed on any Hummer 6.5L electronic injected "drive by wire" turbo diesel between 1996 and 2003. Before you do this it has been reported that the trucks idle will cycle up and down if you put the hazzard flashers on.

Just a quick note. To get a high idle on a 6.5 N/A diesel activate the cold fast idle.

Most manufacturers recommend around 1100 RPM for extended idle periods on diesel engines to prevent carbon deposits. This is particularly handy for warm up (heater) cool down (AC) as well as being easier on the engine if extended idle times are required. I have an array of high power lights I like to leave on when setting up camp in the dark. The lights will eventually drain the battery if the truck is at normal idle.


ECM Shown mounted to the engine cover


Center Connector pulled out of the ECM


  1. Remove the glove box. Actually you may want to remove the whole doghouse.
  2. Remove the center connector by squeezing the connector locks and pulling it out.
  3. Remove the lock on on top of the connector which corresponds to row B. A is the top row & B is the bottom row. The bottom row is on the flat side.
  4. Crimp one or two depending on number of speeds desired 18 ga. wire(s) to a terminal pin (you must supply a pin, p/n12089649) available at any GM dealer for each cavity since they are now empty. Use a Packard Electric crimp tool (p/n 6285847). This tool is available from Pioneer-Standard Electronics @ 1-800-PACKARD. We also found the pins at Pepboys auto (5 for 3.50).
  5. Insert the pin that will be connected to switch #1 with the attached 18-ga. wire in cavity B7 (the 7th hole from the right in the back, "wire side") Insert the pin that will be connected to switch #2 with the attached 18-ga. wire in cavity B8 ( the 8th hole from the right in the back "wire side") Make sure the terminal pins lock into the connector, now reinstall the connector in the PCM.
  6. Attach wire(s) to a switch (user furnished) connected to chassis ground.

Rear of the Connector

Rear of the Connector showing the openings for 2 new pins


Pins you need from a GM dealer cost 1.14 each (2007)

Note: The Fast idle will revert to base idle when the brake is pressed or if the selector is put into gear. The fast idle will resume when the shifter is put in park or neutral.

If you are using LED turn signal and brake lights on your truck you need to install a load resistor under the dash and connect the brake lights to ground or your cruise control and/or high idle switch won't work. There is one switch with 2 connectors on the brake pedal. One is used to remove power to the cruise control (2 wires). The other two wires control the brake lights. One wire on the brake switch goes to power (orange). The other wire goes to the brake lights (red). You attach the wire that goes to the red wire on the brake lights to a 215 ohm resistor to ground. There is an actual AMG 'kit' that comes with a ring lug that is suppose to go under one of the ground lugs on the body pillar. Without the resistor the computer thinks the brakes are on and the cruise or high idle switches will not work.


ECM with Installed wires

ECM with Installed wires

Rear of Switches Finished product
The 2 switches ground B8, B7 or Both to get the 3 idle speeds