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Thread: Vehicle leaning under light acceleration and small TPS

  1. #1
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    Vehicle leaning under light acceleration and small TPS

    Hi guys,

    I am working on tuning my L67 platform vehicle for E85, and I am seeing some enleanment under small (< 20%) TPS values. I've looked all over the fueling tables but I can't seem to find what is causing this. My best guess at this point is AE but the AE vs. TPS Max Delta table doesn't match the behavior I am seeing. Any ideas?

    Restored Disable TPS.hpt
    OLF AFR after disable TPS delta change.hpl

  2. #2
    Tuning Addict 5FDP's Avatar
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    I wonder if the cat test is running as well. HP Tuners can't turn that off but other software like the older DHP and maybe Tunercat can disable that feature.

    I noticed the commanded AFR changing alot even though you aren't in PE at all. Makes it hard to tune the fueling when that is jumping around.

    Your intake temps don't help either, those are getting crazy hot when you aren't moving or going slow. Your filter must be in the engine bay still instead of pulling air from the fender and behind the headlight.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Quote Originally Posted by 5FDP View Post
    I wonder if the cat test is running as well. HP Tuners can't turn that off but other software like the older DHP and maybe Tunercat can disable that feature.

    I noticed the commanded AFR changing alot even though you aren't in PE at all. Makes it hard to tune the fueling when that is jumping around.

    Your intake temps don't help either, those are getting crazy hot when you aren't moving or going slow. Your filter must be in the engine bay still instead of pulling air from the fender and behind the headlight.
    Is there a way to check if the cat test is running? Even before tuning for E85 I would notice that in OL the fueling would move around from 0.97 to 1.05 lambda. Seems like its probably a set AFR adder since now that I am running E85 its moving it up to 1.15 lamda. I have a CAI with a box pulling from behind the headlight, my intake temps have always been that warm during warm months though.

  4. #4
    Tuning Addict 5FDP's Avatar
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    If the commanded fueling is moving around like that, the test is happening. These computers are so basic we can't really see anything about it other than watching the commanded fuel ratio change on it's own.

    The cat test is something that only happens on 2001 computers, it was a non issue on 1997-2000's. There is a way to disable it, just not with HP Tuners.

    If you installed the rear o2 sensor again and spaced the sensor out enough so it didn't trip a P0420 code the test wouldn't happen doing it that was as well.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  5. #5
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    Quote Originally Posted by 5FDP View Post
    If the commanded fueling is moving around like that, the test is happening. These computers are so basic we can't really see anything about it other than watching the commanded fuel ratio change on it's own.

    The cat test is something that only happens on 2001 computers, it was a non issue on 1997-2000's. There is a way to disable it, just not with HP Tuners.

    If you installed the rear o2 sensor again and spaced the sensor out enough so it didn't trip a P0420 code the test wouldn't happen doing it that was as well.
    The car is actually a 2005, however the PCM isn't the original since I had a canned tune in the vehicle before, so I'm not sure what year the PCM is from. Is the test happening because of the P0420 code? What would happen if I disabled that code, would it still run?

  6. #6
    Tuning Addict 5FDP's Avatar
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    Sorry I meant 2001+, so anything newer than 2001.

    You already had P0420 disabled and the rear o2 sensor codes disabled. The test happens because the sensor has been removed and the circuit is open.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  7. #7
    5FDP sorry to butt in but you are very knowledgeable. Do you do remote tuning?
    I would message you but I don't know how

  8. #8
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    Quote Originally Posted by 5FDP View Post
    Sorry I meant 2001+, so anything newer than 2001.

    You already had P0420 disabled and the rear o2 sensor codes disabled. The test happens because the sensor has been removed and the circuit is open.
    So the issue the rear O2 sensor circuit is open? Because I do have a rear O2 sensor installed in the car. I realized I wasn't logging the rear O2 bank, and I added the O2 Voltage B1S2 PID and it reads a voltage, so I think the sensor works. Not sure why it would be an open circuit and running the test then though.

  9. #9
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    So I am still having issues with this problem, I called around to a few local shops as well as ZZP and from what I learned it sounds like it is indeed a cat test running. They thought that the test should only be happening if my rear O2 sensor is missing/faulty, however I am seeing a voltage reading on the B1S2 O2 voltage PID. That is the rear O2 on these cars, right? If so and I'm seeing 0.3-0.5V doesn't that mean its working? ZZP also suggested I could disable a code to stop this test from running but the lady I talked to wasn't able to tell me what code it was. Any ideas?