Is it possible to start the car andnot lose connectivity to the tech 2?
It seems that some of the functions require "start engine".
Thanks
Bill
It seems that some of the functions require "start engine".
Thanks
Bill
Tech 2 reboots when engine is started
chunker941
101 - 114 of 114 Posts
I did not face this issue, but I would first check on the GND-connections of the TECH2 board to the voltage regulator. There are different ones for the input and the output side. Maybe the solution is there...
I think in my opinion that the problem coming because the voltage regulator ( LM2596S ) has the same ground for both input and output , but the original voltage regulator has a separate ground .
could you please my dear brother do a self test for your scanner and tell me if it is passed all the test or not , i know i am bothering you , so forgive me for that
and many thanks for your help
regards
Samer
My dear brother el patron
Many thanks for you and for all your efforts to help all members in this lovely forum
I will wait for your reply , and in advanced i wish to you a very happy weekend bro
Samer
I don`t know how to thank you for every thing , thank you so much for your confirming about the GND FET Error , but i tried to use the scanner and i did not notice any problem caused by this error , and every thing working very good , so i think this error is not a big issue , and it has no effect on our scanner .
and the main important now is that the scanner not restarted any more when the engine off and on again .
my greeting for you and all Germany people .;ol;;ol;;ol;
I think this might be relevant avoiding ground loops when using the scanner on the car, but powered from the net from the building around. I assume this to be no issue when the scanner is only connected to the car.
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670 Posts
Did someone tried this idea?
At first I was interested, but I checked WIS and cigarette lighters are powered by +54, which is only connected to +30 (battery) when ignition switch is in on position and not connected when ignition switch is in start position.
Therefore this would just do the opposite of described idea.
Maybe buck boost power supply has big enough capacitors to buffer very short starting times but when you do longer cranking it will shut down due to lack of supply voltage.
OBD connector below steering wheel has battery voltage directly connnected on the +30 line, therefore independent from ignition switch position.
I would like to avoid opening and desoldering the voltage control module if there is another external solution (apart from connecting the DC/DC converter directly to the battery clamps).
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20,149 Posts
Yes and no. I bought an OBDII extension cable, intercepted the +12v, and inserted the buck-boost converter in the middle. Works perfectly. It was discussed elsewhere on the forum, but I'm not sure where.
The problem with the plan I outlined above is that the Tech 2 prioritizes power from the OBDII port, so if there's power there it ignores all other sources. So, you either gotta cut power from the port entirely, or use it as the source.
A decent dc-dc converter can turn 9v into 12v for an extended period of time. Probably forever. The one in my motorhome turns 14v into 19v for hours at a time. It's not a "buffer" - that's not how they work. 12v@2a or 9v@2.7a is the same on the other side of the converter, and safe for the OBDII power circuit.
The problem with the plan I outlined above is that the Tech 2 prioritizes power from the OBDII port, so if there's power there it ignores all other sources. So, you either gotta cut power from the port entirely, or use it as the source.
A decent dc-dc converter can turn 9v into 12v for an extended period of time. Probably forever. The one in my motorhome turns 14v into 19v for hours at a time. It's not a "buffer" - that's not how they work. 12v@2a or 9v@2.7a is the same on the other side of the converter, and safe for the OBDII power circuit.
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Not sure if that's entirely true about ODB prioritizing. I had power via included adapter directly to battery and worked off of that uninterrupted when unplugging from odb2 to PC for security access and back again.
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20,149 Posts
Sure, that works because you're taking power away from the OBDII port and then the DC jack fills in. But if you have both plugged in and crank the engine, the Tech 2 will restart. It's well documented, well discussed. I observed what you observed which is why I thought the converter on the DC jack would work, but I found out what others did... if there's power on the OBDII port, the tech 2 disregards the dc jack. You can get around that by removing the 12v from the OBDII connector, but I didn't want to mess with every car I needed to use the tech 2 on.
Here is one of many threads on the topic:
https://gmtnation.com/forums/threads/fix-tech-2-reboots-if-engine-started.16563/
Here is one of many threads on the topic:
https://gmtnation.com/forums/threads/fix-tech-2-reboots-if-engine-started.16563/
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670 Posts
Thanks, it was too late to get this idea yesterday. ;ol;
There is probably a misunderstanding. If the DC/DC converter would be plugged to cigarette lighter, it would have been cut off from power supply just in the time of cranking as cigarette lighter is shut off during cranking.
Priorization of the different power supplies would have been my second question, but it is already answered.
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62 Posts
More than 8 years later, I want to say thank you for this mod. Did it to my chinese Tech2 and voilà, no more reboot on engine start.
It was easy to find the DC-DC in an electronic shop as it's clearly pretty popular in the Rapsberry Pi community. I meticulously did the transistor mod - though I'd be curious to understand how it "inverts the logic".
The trickiest part was getting pin #5 off the pcb board without breaking it altogether.
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