Triggered...Using Kaizen Relays with Aftermarket ECUs

As Kaizen Relays are beginning to ship, one particularly curious situation caught our eye enough that we thought we should share our findings: 

Disclaimer: The 'issue' described below, is evident in many aftermarket ECUs, and not just the Haltech Elite 2500 that this particular customer was using. We are not placing blame on any ECU company for their internal hardware design. 

Background: The customer was using a Low Side Digital Output (DPO) from the ECU to trigger a Kaizen Relay. The ECU and Kaizen Relay worked great when the car was on and running, no issues to report. The Kaizen Relays were wired to Battery Constant Power, not Switched Power. 

The Issue: When the customer would go to turn the car and subsequently the ECU off, the Kaizen Relay would suddenly Turn ON. 

The Reasoning: In the Haltech hardware (and many other aftermarket ECUs), each DPO is by default connected to a pulldown resistor, and can be selected via the software to use a pullup resistor instead. See below simplified circuit schematic:

Output Configuration - Default State

When the ECU is ON and software has selected the pullup resistor to be active, the circuit becomes the following:

Output Configuration - On State

But when the ECU is turned off, the circuit flips to a pulldown resistor, like the following:

Output Configuration - Off State
Since the Kaizen Relays are ALWAYS on, due to being wired to Constant Battery Power, the pulldown resistor in the ECU is triggering the Kaizen Relay's Negative Trigger Pin.
The Fix: The same pin from the ECU can be used, but should be configured as a High Side Output, instead of a Low Side Output. Additionally, the trigger wire should be moved from the Kaizen Relay's Negative Trigger Pin to the Kaizen Relay's Positive Trigger Pin. 
Small Note: Haltech advised that during a Firmware Update or a Map Upload, the DPOs go to their powered ON State and therefore the outputs will sit at 12V, so if connected to the Positive Trigger Pin of the Kaizen Relay at this time, the ECU will trigger the Kaizen Relay On as well. 
If you are experiencing similar circumstances, please leave us a comment below or email us for technical support. Thank you for reading! 

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