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PLEASE BE AWARE: The vehicle must be turned off and you must remove the keys from the ignition to prevent power from being applied to the computer during installation. Do not switch your ignition to the run or accessory position during installation (i.e. do not play your radio). Failure to leave the ignition switched off will cause damage to your computer or to the SCT switch chip. Note: Pictures are of a chip, the QuarterHorse install is exactly the same in most regards.


Removal of Stock computer

Remove the negative battery terminal wire. Locate the stock computer. The PCM is held in place by a 7/32” or 5.5mm bolt, this bolt has to be removed first. A 10mm socket is required to remove the wiring harness from the computer. The 10mm bolt is located at the center of the wiring harness. As you loosen it, the connector will slowly release from the harness.

Stock Computer Connector Preparation

Once you have the computer removed, locate the end opposite the wiring harness connector. This end usually has either a small plastic or thin metal cover. Pry this cover off gently. A double-sided flat electrical connector will now be exposed. You will notice the terminals have a conformal coating on them; this MUST be removed THOROUGHLY or the chip will not make proper contact with the computer! To remove the plastic or grease coating covering the terminals, the cover of the computer must be removed (the hole exposing the contacts is not large enough to clean the contacts sufficiently). To remove the cover, remove the hex screws on the body of the computer; the top and bottom of the cover will now lift away exposing the board. Early connectors are covered in white grease, later ones in a plastic film.

It is imperative that the contacts are cleaned properly. Both the top and bottom! Use a tool to scrape and peel as much of the coating off of the connector as you can. Make sure to do this on BOTH sides of the connector. Use an awl, craft knife or paper clip to carefully clean all of the coating from BETWEEN the contacts on both sides.  Do not scratch the metal contacts with the awl, craft knife or paper clip. For grease use clean rags and alcohol.




The chip will attach to the connector in the J3 Port

Remove the cover to access to the connector

On some there is a grease coating




The grease and plastic must be removed

Clean the contacts and between the contacts with a Scotchbrite pad or fine sandpaper

This is what a switch chip looks like

You will now see the contacts clear and free of debris on both sides. The metal contacts have a thin plastic coating or grease over them. This coating is applied at the factory and is normal, it must be removed for the chip to make proper electrical contact. To do this scuff lightly with a Scotchbrite pad or fine sandpaper. Be careful to apply gentle pressure while moving the pad from side to side over the contacts. Clean only enough to remove the coating. As the coating comes off, the contacts will begin to change to a copper color – earlier processors just need to be thoroughly scuffed. STOP cleaning when you begin to see a hint of copper on each contact! We recommend cleaning one contact at a time, to minimize problems or damage to the contacts. Be sure to wipe contacts with a clean, lint-free alcohol soaked cloth followed by drying with a clean dry cloth as a final step. On Fox body (88-93) Mustangs you'll need to bend a small electronic component carefully back out of the way of where the chip will be. You will also have to slightly enlarge the chip port opening in the processor’s aluminum case – tin snips work well, bend the metal back after making a couple of cuts. Try the chip in the slot to see how much metal to cut – use the chip as a template .

Please verify that BOTH sides of the edge connector were cleaned thoroughly. Improper cleaning is the most common reason chips fail or work incorrectly.


Installing the Chip

Note: This is a single program chip, you will not have a cable.



Slide the switch connector cable into the chip

The proper orientation of the chip is with the circuit board of the chip and the switch cable on the larger side of the J3 port opening



The chip properly installed with the correct orientation. Note the position of the switch cable in the larger side of the J3 port.

This is a close-up of the switch set top position “0”

Once you have properly mounted the chip, secure the chip to the computer with 2” wide package sealing or duct tape.

Re-installing Computer

Return the computer to its location. Be sure the box holding the computer in place does not bind the chip and cause it to tilt. Re-connect the wire harness. Test the vehicle by starting the engine. If it starts OK then, secure the computer to the metal bracket with the original bolt or by using tie wraps. Install the switch in a convenient location, such as a glove box. Secure the wires with zip ties. Reconnect the negative battery wire.

On EEC IV Cars (89-95 Mustangs) the chips assumes stock timing (10*) and stock fuel pressure (39.5 with the hose off and blocked just to measure it).