RCP/Mk3 causing OBDII interference

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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!

[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.

[brentp]

Glad you figured it out!

[HomebuiltRacing]

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]

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,