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Thread: P0098 Roush tune with VMP GEN2R

  1. #1
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    P0098 Roush tune with VMP GEN2R

    Hi, I have a 2017 with VMP GEN2R kit. I was running VMP tune for about a year and decided to try my hand and learn to tune. I found a Roush tune that I have been playing with, problem is I am getting P0098 DTC code. I have the VMP IAT relocation harness kit and just bought a second one for trial and error. Still getting the code. When I load the VMP tune back in I don't get the code. I have logged the volts and IAT temps and they are very close to IAT transfer data that is in the Roush tune. IAT seems to be working fine. the VMP tune is locked and I cant look at their IAT temp transfer data and I emailed them but haven't heard back. Any ideas? Thanks Rob

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    Thank for reply, but can you expand on that. Are you saying the MCT transfer is for IAT2? Like I said my IAT is working correctly and my IAT2 shows -40. As far as I can see things, IAT2 doesnt have any authority as far as pulling or adding timing.

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    Should I disable mct sensor then?

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    MCT Switch ECM 2559 under Engine diagnostics General - set it to enable if you are using VMP IAT harness.

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    Yes sir it was already enabled and was getting dtc code..

  7. #7
    Senior Tuner CCS86's Avatar
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    If MCT switch is enabled, and you are seeing -40 on your IAT2 signal, your wiring is wrong or your sensor is bad.

    How are you concluding that IAT2 has "no authority"?

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    That what I am thinking. I see nowhere in the strategy where IAT2 has any function. I am assuming if it had a advance/retard function it would have a multiplier. Am I assuming right? And yes I am showing -40 on IAT2.

  9. #9
    Senior Tuner CCS86's Avatar
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    You don't have access to see which channels are mapped to which channels. You are just looking at labels manually put there by HPT. Don't make assumptions like that. If the MCT switch is on, the PCM is most definitely mapping IAT2 to various IAT based tables/multipliers.

    That "-40" reading is your problem. Fix that.

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    Hmmmm, Thank You for the input. This is the reply I got from Joe at VMP.

    We use a harness to put IAT2 in through the MAF harness in the IAT1 connection.
    If you are using a Roush strategy, you need to use a Roush sensor and harness.

    When I google Roush IAT harness and sensor all that pops up is VMP harness, which I already have. Im understanding the VMP harness moves IAT to under the heat exchanger and does away with IAT2, also it says the VMP harness is for Roush/Whipple running aftermarket tunes. Trying to wrap my head around this....

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    2DF0EFDB-1117-4D5A-9BB2-B49956D57158.jpg....


    Just happened onto this harness.

  12. #12
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    obvious you need to disable iat2 / mct

    in the actual code either iat2 or iat is loaded in to the mct temp register and used as the input for the borderline knock act value for the multiplier table and function.

    if mct isnt present then iat is used for the input. If mct is present but iat2 failed then the default failed act2 value is used as the input.

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    Thanks a bunch for the input.....Cheers

  14. #14
    Senior Tuner CCS86's Avatar
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    Yup, best bet is to leave MCT switch on and get the proper Roush harness.

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    Senior Tuner veeefour's Avatar
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    IAT is build in MAF sensor - you don't need any extra harness juist cut and reroute two IAT wires. There are 5+1 wires in the MAF connector: 3 for MAF and 2 for IAT.
    Last edited by veeefour; 07-08-2019 at 12:32 AM.

  16. #16
    Senior Tuner CCS86's Avatar
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    Quote Originally Posted by veeefour View Post
    IAT is build in MAF sensor - you don't need any extra harness juist cut and reroute two IAT wires. There are 5+1 wires in the MAF connector: 3 for MAF and 2 for IAT.


    You don't "need" a harness. It's for people who don't want to cut OEM wires.

    There is still benefit to keeping both IAT1 and IAT2 live. Like checking the delta between them to gauge IC system performance, and allowing MAF Temp comp to function correctly if you choose to use it.

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    Thanks all for the input. Came across a OS that supports the VMP IAT relocation. When I get home in a week I will dig into the new OS and start making tune adjustments. If by chance the new OS doesn't work, then I will load the Roush OS back in and go with you're fix. Thanks again. Cheers

  18. #18
    Senior Tuner CCS86's Avatar
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    You don't need to switch OS.

    Option 1: Leave IAT2 routed into the MAF harness and disable the MCT switch.

    Option 2: Restore MAF sensor wiring, route IAT2 into the PCM connector, leave MCT switch on. (better)

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    Cool. I will keep option 1 open. Since I a newbie to tuning it gives me a chance to do some learning changing OS’s. If I run into any issues I will look at your options. Cheers Rob

  20. #20
    VMP harness connected to OEM MAF/IAT - MCT switch disabled.
    Roush harness/IAT sensor, MCT switch enabled.

    For those who recommend just cut pins in maf and wire it to Roush IAT sensor, looks they never did that. MCT connected IAT, like Roush is DIFFERENT resistance than OEM maf IAT sensor! Thats why you need to buy IAT from VMP or any other automotive shop if you know exact value needed, it costs 10USD.
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