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ECU Hold Power Wiring |
  
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ECU Hold Power Wiring |
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ECU Hold Power (Keep Alive)
This wiring method allows the ECU and engine management system to remain powered after the key has been switched off. This allows shut down tasks and the ISC stepper motor (if used) to be reset to the appropriate position for the next start up. The ECU will shut down the system when reset is complete.
ISC Stepper Motors
This wiring method should be used when an Idle Speed Control (ISC) Stepper motor is wired.
The other alternative is to reset the stepper motor at key-on, which can cause excessive over-rev on start up or extended cranking periods.
Other Uses
ECU Hold Power can be used to keep the ECU powered for a fixed period of time after the ignition has been switched off. This can be useful for running cooling fans and electric water pumps.
All Link G4+ ECUs except the Thunder (refer below) can be wired for ECU Hold Power as shown below
How it works:
| 1. | The ignition switch is turned on, powering the ECU through the external diode. |
| 2. | The ECU powers up and switches the Main ECU Relay on. |
| 3. | All systems are powered through the relays now and run as normal. |
| 4. | When the ignition switch is turned off, the ECU senses this through its Digital Input. |
| 5. | The ECU resets the stepper motor to its default position (if fitted), then shuts off the main relay when it is ready causing the system to power down. |
The following items must be set-up in PCLink Tuning Software when using this wiring. This should be done on the bench before installing the ECU to prevent damage to the diode as it will be powering the system until ECU hold power is set up.
| · | The appropriate Digital Input must be configured as 'Ignition Switch'. |
| · | The appropriate Auxiliary Output (or Ignition or Injection channel) must be configured as 'ECU Hold Power'. |
| · | The ISC Control 'Stepper Reset' function should be set to 'Key OFF'. |
The correct operation of this wiring system can be tested by listening for a pause of a few seconds between switching the key off and the ECU and Main relays switching off. The ISC stepper motor may also be heard operating during this period.
ECU Hold Power Wiring Method 1
ECU Hold Power Wiring Method 2
NOTE: For method 2, an Injector or Ignition driver must be used for 'ECU Hold Power'. Do not use an Auxiliary driver.
Link G4+ Thunder Wiring
Thunder ECUs incorporate a special Main Relay Driver circuit as well as a dedicated ignition switch input. The advantage of this is:
| · | The diode shown in the circuit above is built into the ECU. |
| · | The driver is isolated and can not cause back feeding. |
| · | The driver is differential so can operate a high side or low side driven relay. |
| · | A Digital Input and Auxiliary Output are not consumed. |
Thunder Hold Power High Side Wiring
Thunder Hold Power Low Side Wiring
Link G4+ Kurofune Wiring
Unlike other ECU's, Kurofune has Auxiliary 11 for controlling the internal hold power circuits. All of the PCLink instructions above apply, except Aux 11 must be set to 'ECU Hold Power'.
Kurofune Power Wiring with ECU Hold Power