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Thread: Limp Mode

  1. #1

    Default Limp Mode

    TestLimpModeIssue20201010.zip
    My car is going into limp mode ever since I upgraded to V5 build 140. I was told that V5 added safety features for DBW. The only time it seem to happen is when I press the throttle to 100% quickly. If I gradually press the throttle to 100% it doesn’t seem to fail. I read that it can be caused by the ECU losing the signal (bad ground) from the DBW. I have connected the ground from the DBW to the Holley ECU. I've checked resistance ground. The car sat for a year and I decided to get it out and fix some issues with it. One being limp mode. I upgraded to V5 build 160 for some features that I wanted. After I was done I took the car out and drove it mildly and it went into limp mode as I was starting to accelerate from a stop. I cycled power to the car and proceeded to take off and as it shifted to 2nd gear it went into limp mode again. I got it home and cycled power again and let it idle for about five minutes. Setting in the car it went into limp mode again. There doesn’t seem to be any one thing I can do to get it to go into limp mode. After reading the forums I decided to clear my datalogs and run the car until it go into limp mode. After a couple of hard accelerations it went into limp mode. So I've attached the datalog and the Global File and hope that someone can help me. Thanks for looking. One thing in the datalog for TPS #2, the High limit is 100, but TPS #1 is 5. Dominator ECU, V5 build 160, 402 ci, LS2 harness, DBW, 4L80E transmission.

  2. #2

    Default

    I'd check the TB connector and make sure that all the pins are firmly seated. Also make sure that the wires are in good shape.

    I looked at your tune, and I'd consider rescaling the load axis so that at least half the table is devoted to N/A and half to boost. This is unrelated to the limp mode issue, but I thought I'd mention it.

    You may also think about upgrading to V6 as they have relaxed some of the DBW parameters, which might solve your limp mode issue. Andrew

  3. #3

    Default

    Thank you. All wiring and connections are good. I should mention that it’s a turbo car which you saw in the Global File. I was looking at my Learn Table and the values don't look correct nor does the Base Fuel Table. After this post I started the car and it went into limp mode after 10 seconds without doing anything. I wonder if it has to do with AFR in the tables. I had it tuned pretty well on a dyno last year and that's when we found the limp mode issue at WOT.

  4. #4

    Default

    The Target AFR table has nothing to do with the limp mode issue. How is the red/white wire from the DBW harness connected? To be clear, limp mode disables the DBW pedal completely and fixes the TPS to 22%. With limp mode, pressing the pedal does nothing. Is that what's happening? Andrew

  5. #5

    Default

    Yes, exactly.

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