RCP/Mk3 causing OBDII interference

Discussion and research on OBDII integration, especially on OEM specific PIDs from Ford, GM, Chevrolet, BMW, Porsche, Audi, Toyota, Volkswagen, Mazda, Honda, Subaru, Mitsubishi and others.
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Dadspeed
Posts: 14
Joined: Sun Mar 18, 2018 3:56 am
Location: Champaign, IL

RCP/Mk3 causing OBDII interference

Post by Dadspeed »

Hi!

I have a RaceCapture Pro/Mk3 in my 2004 Mazda RX8 race car. I have had some trouble getting OBDII and CAN PIDs working on it. Additionally, the car has refused to rev above 8k, hitting a wall at that speed and showing signs of some electrical problem. I've really been pulling my hair out over this.

Today I hooked up a nice OBDII code reader what will show me the PIDs live. With the engine off and key 'on,' everything looks fine. When I turn on the Pro/Mk3, the PIDs go haywire. The readings are all over the place, and even PIDs marked 'N/A' show funny readings.

Same thing when the car is running, of course. And now I find out that the car will run all the way up to the normal redline with the Pro/Mk3 turned off.

I wonder what I've hooked up incorrectly. The only four wires connected on the Molex are power, ground and CAN high/low. What might I have done wrong? Do I need to change settings in the Pro/Mk3?

Thanks!
TT5 Mazda RX-8

Dadspeed
Posts: 14
Joined: Sun Mar 18, 2018 3:56 am
Location: Champaign, IL

Post by Dadspeed »

Okay I seem to have tracked the problem down. The OBDII PIDs I had set were not using 'passive mode' in RaceCapture. Setting all of them on passive seems to fix the problem entirely. I still need to make sure the car runs correctly with the Pro/Mk3 turned on, but I feel like this should work. It's not messing with the OBDII PIDs the way it was before.
TT5 Mazda RX-8

brentp
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Post by brentp »

Glad you figured it out!
Brent Picasso
CEO and Founder, Autosport Labs
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HomebuiltRacing
Posts: 6
Joined: Mon Dec 30, 2019 10:36 am

Re:

Post by HomebuiltRacing »

Dadspeed wrote: Fri Apr 13, 2018 1:59 am Okay I seem to have tracked the problem down. The OBDII PIDs I had set were not using 'passive mode' in RaceCapture. Setting all of them on passive seems to fix the problem entirely. I still need to make sure the car runs correctly with the Pro/Mk3 turned on, but I feel like this should work. It's not messing with the OBDII PIDs the way it was before.
I have similar problem and if I set "passive mode" for requested PIDs I just don't have any info in log, how this mode supposed to work? Should I also change something else in the settings?

brentp
Site Admin
Posts: 5986
Joined: Wed Jan 24, 2007 6:36 am

Re: RCP/Mk3 causing OBDII interference

Post by brentp »

Passive mode means that it's listening to OBDII responses made by another OBDII device -- like it's spying on the data, passively.

The early RX8 ECUs have a problem handling the OBDII queries we generate; the best alternative is to use the RX8 direct CAN mapping, which listens to a stream of CAN data separate from OBDII. See the CAN mapping preset available under Setup / CAN mapping.

Hope this helps,

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