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PC link wont connect, Car starts and runs intermittently/inconsistently


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I am running the G4X HC92X.

The car has been sitting a couple months in the garage after a successful track day. I went to start it on Saturday and moved it to my shop, across the yard with no issues.

The next day I go to start it and tries to start, turns over once then dies. Try it again and the radiator fan kicks on when I turn the key to the on position. I unplug the fan and try again. The car fires right up, I plug the fan back in while it's running, fan does not turn on and the car runs like normal. Turn the car off then back on and it starts again just fine. So I go for a drive and everything seemed normal, thinking it's possibly a sticking fan relay maybe pulling too much power on start up.

I get to where I'm going with out issue. The car sits for a few hours then when I go to start it, the car is in limp mode and wont rev passed 2500 in gear. I stop, turn the car off then pull out my laptop to see what's going on. It won't connect to the PC Link. Saying "The USB device connected to this PC has malfunctioned and windows does not recognize it." So I let the car sit for a little bit, attempted to unplug the fan again and it would turn over once then die. Eventually just let it sit for a bit and it started up just fine again and I got the car home running like normal. 

Since being home it still wont connect. I have tried updating the PC, Tried installing the new PC link software and drivers, troubleshooting/repairing the USB port, but other usb devices connect just fine. 

Any ideas? 

I am getting full 12+ volts to D-2, A-25, and B-1. There are 2 solid blue lights on the ECU with the key on.


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The first thing I would try is to remove it from the car, plug in the laptop and check in windows device manager that a Link ECU is showing in the coms port category.  Assuming device manager looks ok then power it up on the bench with a couple of jumper wires.  See if the laptop then connects.  This is the quickest way to rule out a power supply issue as sometimes just a voltage test with no load doesnt give the full picture.  

+12V on B1 and Gnd to D21 are probably the safest options as you can access the pins on the backside of the header.


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Just tried it and it's still saying USB malfunction. I am going to borrow a friend's PC to rule that out too. This is the only PC I own.

When doing this I also get codes 101 (long blink and one quick) and 107 (long blink and 7 quick), I am assuming that's because they are not connected?

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Yes fault codes are expected with everything unplugged.  For testing the USB error with another PC, you dont actually need to power the ecu up, the ECU should still show correctly in windows device manager whenever the USB cable is plugged in. 

Can you confirm the USB cable is definitely plugged into the socket on the top PCB, not the CAN port on the bottom board.     


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Correct, the usb is plugged into the one on the board as you have pictured since Ive been running this ECU. 

I tested it on another PC with a fresh install of PC link and I am getting the same USB malfunction code.

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