FIX: Tech 2 reboots if engine started

Mooseman

Moderator
Anybody else have this issue? If you have the Tech 2 plugged into the OBD port and start the engine, it shuts down and reboots. Doesn't matter if I use an external power source (AC or seperate battery) and I confirmed it's not using the OBD port's power.
 

littleblazer

Gold Supporter
Mine does it as well. Never figured it out.
 

Sir ffeJ

Well-Known Member
I heard clone Tech 2's do this.
 
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Mooseman

Mooseman

Moderator
Well that's not good :cry::cry:
 

littleblazer

Gold Supporter
I don't remember but I think if I use the ac adapter it doesn't shut off.
 
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Mooseman

Mooseman

Moderator
Did some reading and according to this, it can apparently be done by disabling pin 16 in the OBD port and using an external 12V power source. Maybe pulling the relevant fuse might also work. I'll have to give this a try as I am not up to taking my Tech 2 apart.
 

littleblazer

Gold Supporter
Mine won't power up from just the obd port anymore... it self moded lol.
 
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Mooseman

Mooseman

Moderator
Thanks to @Sir ffeJ , I did some research in those links and I can confirm that if you pull the fuse that supplies 12V to the OBD port (fuse 13 LTR under hood for GMT 360's), you can start the engine and it won't reboot. Here are the steps:

  • pull the fuse that supplies power to the OBD port
  • plug the Tech 2's connector to the OBD port
  • using either the AC adapter or 12V battery clip adapter, connect the round power plug into the round power hole in the wire connector near the CANdi unit
  • power up the Tech 2 as usual and conduct your tests.
  • After disconnecting the Tech 2, don't forget to replace the fuse

Do not use the power plug in the Tech 2 itself. I tried that one and the CANdi unit wouldn't power up. Using the one in the cable connector fixes that. I used a mini engine start booster with the clips.
 
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Mooseman

Mooseman

Moderator
Final fix for this so you don't have to hunt for the fuse. I bought an OBD extension cable and added a switch to the pin 16 wire. Using an external power supply to the Tech 2 using the plug hole on the cable near the CANdi unit, it works flawlessly.

Funny thing though, with the external power connected (I used a lithium booster pack), it worked perfectly whether the switch was on or off, as if using the external power plug cuts off the OBD vehicle power. It's funny because it didn't work before. Oh well, either way, I have the switch.
 

j-bone

Well-Known Member
mooseman for the win!
I ran into this problem tonight while trying to run evap test .
for anyone looking to solve this problem I would suggest doing what mooseman did or as I did which was to have a battery on the passenger side ( I had a small lawn tractor battery ) and disconnect the fuse and run the tech 2 that way .
i'm glad I did it this was and not run the wall adapter because I needed to drive the car for part of the test.
it is very important you remove the fuse because when cranking it can pull power from your alternate source , i blew the 3A fuse in the alligator clip leads .
 

JayArr

Well-Known Member
Interesting that it pulls power from the temp battery, enough to blow the fuse. This could indicate that the reboot is simply because the voltage the OBD port is supplying drops below a threshold in the tech II and that's what's causing the reboot.

My suspicion now is that the clones have inferior power supply regulator circuits. When I get a chance I'll pull mine apart and see if there is an easy circuit fix inside.
 
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Mooseman

Mooseman

Moderator
There is an updated DC-DC power regulator that I replaced but it didn't help. Since then, I have found that plugging a power supply into the CANdi's connector bypasses the port's voltage. Don't know why it didn't do that when I first looked into this.
 

JayArr

Well-Known Member
Can you give me a link on the updated regulator?

Maybe the Candi's port power doesn't disconnect the OBD port power unless the regulator has been replaced.
 
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Mooseman

Mooseman

Moderator
Possibly. I would have thought it was a simple mechanical disconnect in the power plug itself.

This video shows how to replace it and lists the part in the comment. The fix is for a no power situation.


Part is Mornsun VRB1205LD-15W or VRB1205LD-15WR2
 

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