[ThreeCW]

Here is some more on HPD ... not sure if this will help with your troubleshooting or not.

High-pedal-disable (HPD)
The HPD feature prevents controller output if the controller is turned on while the throttle is not in neutral. The controller can be programmed to have HPD based either on brake/seat switch input or on KSI.

Brake-type HPD
To start a vehicle with brake-type HPD, the controller must receive a brake/seat switch input before receiving a throttle input. Controller operation will be disabled immediately if pedal demand (throttle input) is greater than 25% duty factor at the time the brake/seat switch is closed. Normal controller operation is regained by reducing the throttle demand to less than 25%.

Sequencing delay, which can be set with the handheld programmer, provides a variable delay before disabling the controller. If the brake/seat switch is opened while the throttle is above the HPD threshold (25%), HPD is not activated if the brake/seat switch is then closed before the delay time elapses.

KSI-type HPD
The HPD feature can be activated by KSI input instead of brake/seat switch input, if preferred. To start a vehicle with this type of HPD, the controller must receive a KSI input before receiving a throttle input.

KSI
KSI (Key Switch Input) provides power to the controller’s logic board, and initializes and starts diagnostics. In combination with the brake input, KSI enables all logic functions.
Some vehicles may have no keyswitch (KSI simply tied to B+) or may have the key permanently turned on.