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Thread: More OBD-II infos

  1. #1
    FLAC cproaudio's Avatar
    Join Date
    Aug 2002
    so cal 2 hours from everywhere

    More OBD-II infos

    I have the Tricom scanner from Alex C. Peper at I chose the Tricom because my 97 Tacoma is not my final project. I'll be changing the vehicle sometime in the future. The Tricom will read ALL OBD-II protocols so I'm set for any type of vehicle I plan to buy in the future. I have used it to scan my friends cars ranging from Toyota 96 Tacoma (VPW) Sienna (ISO9141), Sequoia (ISO9141), Tundra (ISO9141), 2001 Tacoma (ISO9141), GMC P/U (VPW), Ford Ranger (PWM). All worked flawlessly. For some reason, Toyotas have much higher engine load and throttle position at idle speed.

    here are some additional infos

    There are 3 OBD-II ptotocols, VPW, PWM, ISO. If you're sure that you're gonna use the scanner for only one car, then a single protocol scanner would work for you. It'll save you some money. If you think you're gonna use it in different cars later on, maybe trading in your current car and get a different car, then you should get an all in one reader. The software is configurable to read 1 protocol (faster) or auto detect 3 protocols (slower) on initial connection.

    It is safe to leave the OBD-II scanner plugged into the OBD-II port all the time. When you run the obd scanner software, the scanner sends a request to the ECU then it sends the info back to the CarPC. It's read only so it doesnt change anything to the engine computer. More info check
    OBD-II Permanently Connected

    Update speed. When I first got my scanner going, the update speed was about once a second (software default). It was barely tolorable. It's fine for freeway driving b/c VSS, RPM dont change that much. For street, it was a bit on the slow side. When I first take off from a dead stop, it would show 0MPH, then when the screen refreshes it's showing 15MPH then 22MPH and so on. There are 2 things you need to do to increase the refresh rate, limit the data you want to view and decrease pause time between requests. Instead of sending request of all the data, request only the data you want to use such as RPM and VSS. For example, My tricom is capable of sending 40 requests per second. This means if I only send request for RPM, my RPM will take 40 readings in 1 second. That's pretty damn fast. If I send request for RPM and VSS, the refreshment will be 20 times a second Still pretty fast. If I send request for all the sensors, the refresh rate would drop down to 2 updates per second. 2 pr second is not fast but it's tolorable during normal driving. Second way is to decrease the time in between the requests. For example. If the scanner has a 50millisecond pause between requests, the scanner will send 20 requests per second. This means you'll get 20 readings per second. If you decrease the 50 millisecond pause down to 25 milliseconds you'll get 40 readings per second.

    Some OBD-II scanners also clear check engine codes which I think it means they'll write to the engine computer. I feel much safer with a scanner that's read only. I dont wanna f'up my ECU. I can clear my check engine code by disconnecting the battery for 10 seconds.

    Anything else I find I'll update this post.

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  2. #2
    Low Bitrate
    Join Date
    Nov 2003
    Sugar Land, TX
    wow...looks like ther are a ton of threads that should be moved!

  3. #3
    Maximum Bitrate owenjh's Avatar
    Join Date
    Nov 2003
    I say we sticky this, lots of good info in easy to find and read format
    Thanks crpoaudio
    CarComputer Status: New Car & Broken (Motherboard Fried)
    Owen JH | My Linux Blog | The Tech Fellows


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