How do I finish wiring cruise control on a DBW LS swap with a PSI harness?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

• Holley requires using only the supplied drive-by-wire wiring harness; it cannot be cut, shortened, lengthened, tailored, or modified under any circumstance because it contains protective shielding and grounded cabling. (Holley)
• On a Terminator X ECU, the drive-by-wire harness plugs into connector location J3. (Holley)
• The Terminator X brake-switch wire is a gray wire wired to the brake light switch; it must be fed from a +12V source and must see +12V when the brakes are applied, and this input is used to unlock the torque converter. (Holley)
• Holley's DBW system uses the brake-pedal switch as a safety: if the brake pedal is depressed enough to activate the brake light switch, the ECU will not allow throttle position over 10 percent no matter how far the pedal is pushed. (Holley)
• Holley warns not to run the drive-by-wire harness past high-voltage or noisy sources. (Holley)
• Rostra's 250-1881 installation specifies pedal sensor voltages: primary 0.75-0.79V at rest and 3.5-4.0V at full throttle, secondary 0.30-0.40V at rest and 1.8-2.1V at full throttle. (Rostra Precision Controls)
• 242; LS1, LM7; 1999-2007: The Current Performance 24x DBW harness exposes bare wires in documented colors: 12V switched pink/black, fuel pump gray (20A fused), tachometer white, speedometer dark green/white, check engine brown/white, fan 1 dark green, fan 2 dark blue, and brake switch purple for TCC lockup control. (Current Performance Wiring)
• E67, 0411, 242: A brake switch is required for proper drive-by-wire throttle control and TCC operation on PSI's DBW harnesses; the switch should be closed (electrically connected) when the brakes are being applied and open when they are not. (PSI Conversion (via manuals.plus))
• E67, 0411, 242: Incorrect brake-switch wiring on a DBW swap can produce an inoperable throttle condition. (PSI Conversion (via manuals.plus))

Confirm against the instructions for your exact parts before wiring. More: Throttle (drive-by-wire) in our tuning guide.