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kendoka kendoka is offline
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Default JB4 and other OBD2 readers/CAN bus devices - 07-04-2016, 11:41 PM

Hi,

I just installed the JB4 in my 320i, and so far I'm very pleased with the performance. I'll probably post some logs soon to make sure everything looks good.

I've read conflicting information about whether I can use other OBD2 readers at the same time as the JB4. I've seen some posts here and elsewhere that state that JB4 blocks communication for other readers, but some people claim they've been using readers without a problem (might be different/older models, but it wasn't clear to me).

First, I've seen multiple photos of the OBD cable that comes with the JB4 to be a pass-through connector, but the cable I have received was just a standard plug instead. To try tings out, I got a splitter cable from Amazon.

What I've found is actually that when I have another bluetooth OBD reader module connected, everything seems to work fine (i.e. I can see live updates of rpm etc when I log through JB4 with the USB cable). However, as soon as I connect my phone (torque app) to the reader (presumably this means that the OBD module actually starts talking to the ECU), JB4 logging stops updating. The first question is, does this mean that the tuning is not working? And in addition, what exactly causes this state? I know the CAN bus allows multiple devices and they're supposed to play nice with each other using the usual tri-state logic. What exactly causes the interference between JB4 and the other device, and what would the other device have to do to avoid this?

Afterwards, when I disconnect the app, nothing changes, and updates do not resume. Even when I pull out the reader from the OBD port, updates in the JB4 software don't resume. The only way I've found to resume updates is to turn off the ignition and then turn it back on. So, the question is, does the JB4 really stop all communication with the ECU once it's been "disturbed" once, and is there a way to "reset"/restart it?

For example, what would be necessary in order to have another device on the bus that intermittently polls some values without disturbing the JB4 (e.g. maybe only when the car is stopped?)?

Thank you for your help!
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Terry @ BMS's Avatar
Terry @ BMS Terry @ BMS is offline
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Default 07-15-2016, 04:26 PM

The JB4 requires exclusive OBDII access to function properly.


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It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.
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Spec_n20 Spec_n20 is offline
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Default 12-17-2018, 02:58 AM

I'm currently just running map1 and dont really use the other obd2 functions. Can I leave it unplugged for a p3 guage? Or will it be conflicting and bad for the engine?

Last edited by Spec_n20; 12-17-2018 at 03:13 AM..
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Terry @ BMS's Avatar
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Default 12-17-2018, 09:58 AM

You could but frankly the best option is to use the P3 gauge for analog boost only and not attach it to OBDII at all. He has an option for that.


Burger Motorsports
Home of the Worlds fastest N20s, N54s, N55s, S55s, N63s, and S63s!

It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.
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Spec_n20 Spec_n20 is offline
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Default 12-17-2018, 03:43 PM

Thank you ��
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