ECU Hold Power provides a means by which the ECU can control its own power supply relay. This allows the ECU to remain powered after the ignition switch has been turned off and then shut itself down when ready. This is useful for functions such as returning an ISC stepper motor to its home position before the next startup. The following is required in order to use the ECU Hold Power function:
·The Ignition Switch functionality must be wired in and set up, this is required to allow the ECU to detect when the driver has turned the key off and shut the engine down.
·The ECU must be wired to allow it to control its own power. Refer to the Wiring and Installation manual's ECU Hold Power section for further details.
·An Auxiliary Output must be wired to control the main relay and configured as ECU Hold Power. This Auxiliary Output must be selected in the ECU Hold Power Output setting
Operation
ECU Hold Power will keep the ECU powered while the following conditions exist:
·An Auxiliary Output is configured as ECU Hold Power AND
·The Ignition Switch Digital Input is On OR
·The Ignition Switch Digital Input is Off AND
·The engine is still rotating OR
·The ISC stepper motor is resetting (if used and configured to reset at key off) OR
·A special function that is performed at key off is completing OR
·Keep Alive Time has not been reached yet.
Settings:
Output - Sets which Auxiliary will be used to control the ECU power relay.
Keep Alive Time - Sets the amount of time the ECU will remain powered after the engine has stopped. Setting this to zero will stop the ECU from using any timed delay at shut down.
Kill Until Stalled - When the Ignition Switch is turned off, fuel and ignition are disabled. If this setting is set to No, fuel and ignition will be re-enabled if the key is turned back on while the engine is slowing to stop. If this setting is set to Yes, fuel and ignition will not be re-enabled until the engine has completely stopped (RPM equals zero). This setting should typically be set to No to allow the engine to restart if the key is turned back on, particularly if there might be a situation where the driver may turn the key off then back on while the vehicle is moving and overrun will prevent the engine from stopping. If a momentary switch is used for the Ignition Switch digital input, then this setting should be set to Yes otherwise the driver would need to hold the button until the engine has completely stopped.
Runtime Status
Status Values:
·OFF - ECU Hold Power is not used.
·Inactive - ECU Hold Power is used and ECU is being powered normally (Ignition Switch is on and ECU is driving power relay on).
·Active - ECU Hold Power is keeping the power relay on but the Ignition Switch is tuned off and the shut down sequence is happening.