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R53 Mini G4+ ECU Disconnects during engine starts


WrcScooby
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Hello all, 

I am new to running link ECU’s for engine management and would like to say hello to all the fellow performance enthusiasts. 

Does anyone know if there is a way to prevent the R53 Mini G4+ Plug and play ECU from disconnecting or going offline during engine starts? Would this be a configuration issue or wiring problem for power to the ECU? 

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It would possibly suggest there is a large voltage drop on either the ignition switch input or the DME relay input.  

  1. Pin 118 is a 12V signal from the ignition switch, this drives a mosfet inside the ECU which controls the main DME relay.  If the voltage on pin 118 drops below about 7V during cranking then the mosfet will no longer have enough voltage to keep the main relay closed.   
  2. Pin 120 is the main 12V supply from the main DME relay that powers the ecu and most other 12V engine devices.  Voltage dropon this pin is a bit more tolerant but the ecu will switch off somewhere around 6.5V.

A multimeter is generally not fast enough to capture a short spike of low voltage during cranking so an oscilloscope would be the most useful tool to find the culprit.  You could try setting up ECU logging to record battery voltage at 100Hz, which in theory would show voltage on pin 120 just before the ecu shut off, but there is quite a bit of filtering on the bat voltage channel so that may not be a great test.  Maybe somewhere to start though.

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