New here! Need help with 6.4 and mini maxx

Hello everyone, I'm really glad to have found this forum. I'm new to diesels and tuning and need some help. I bought a used 08 F250 a few months back and have some issues I'm trying to fix with my mini maxx that came with the truck. It has 133k on it and is fully deleted. It has a level kit and f350 rear block with 35" nitto trails. My main issues are:
1, The cruise control does not work. I did research and believe it has to do with the tuner.
2, And what are the best settings to get maximum fuel economy? The truck is getting between 10-11 mpg avg with both the mild and hd300 tunes. I use the truck to tow a 4500 lb landscape trailer daily and get worse fuel economy than my f150 5.0. Also power is not as expected. I feel I'm doing something wrong for sure.
I attached a picture showing current version and settings. Any advice would be greatly appreciated! Thanks


  • The first thing I noticed is you're running a very old tune version (TV). You're running 6.4.39. The latest is 6.4.52. Unfortunately, you can't use the updater or if will brick your tuner. You could call Berk's Diesel and see if they can sell you an updated SD card. Get that, install it in the head unit, update the firmware, then load the tuning back to the truck.

    With that said, the cruise control will stop working when you upload the truck to change tune groups or options you can only change during the upload process. It will usually start working after a few hundred miles. Did it ever work since you bought it? There is also a sensor on the brake booster that sometimes fails. If it's out the cruise will not work. It senses when the brake is applied. When activated it turns off the cruise. Example, you have the cruise on, and you tap the brake pedal to kill the cruise. That's the sensor that does that.

    On the fuel mileage, there is one parameter that affects this. It's called Low Boost Fueling (LBF). It can only be changed during the loading of the truck. Default is 3. Best mileage would be set to "0" and the worst "5". This settings helps you get going from a stop by adding additional fuel to combat turbo lag. It also will cause additional smoke as more fuel is introduced to the motor. The best fuel economy would be probably achieved by trying either the Mild of HD300 on stock with LBF at 0. Others report running HD300 on performance with LBF set to 0. All trucks are different so it might take a little experimenting. LBF on 0 is the main factor.
  • Thank you Smokin08 for the reply! I called Berks and left a message. I also called my local diesel shop and they told me they could update my tuner but it's a gamble if it works or locks up. I might just stick with the current firmware for now.

    The truck did not have cruise when I bought it. I went for a test drive on the interstate and the button to set cruise to stand by doesn't even light up. I need to remove the tune and go stock to see if the cruise returns or not. That way I can move forward if it's the tuner or in the truck itself.

    The previous owner had the truck tuned to mild tuning and had it set on hot. The LBF was at 3. I since changed it to HD300 and stock and hot. LBF is now at 0. But fuel use got a bit worse. I want to try Mild tune and LBF 0. That should help it.
    The other settings I had questions on are
    What number do I put in for 295/65/20 nitto trails? I put in 35.50 but don't think it's right.
    What do I do with the transmission tune? and which settings for it?
    And also which settings for psi, pyro, coolant etc.. ?

    Thanks in advance!
  • I can assure you that if you use the updater, or your local diesel shop uses it, the tuner will brick. It's not a gamble. It will. Places like Berk's have SD cards that were good before the bug was put in the updater, therefore the reason I suggested them.

    As for returning the truck to stock to test the cruise, that's not going to work. The truck won't run if set at OEM stock and the DPF is removed. It will start once and then will not start again after that. If the PCM can't read the sensors it needs in stock configuration it will shut down. I would change the sensor on the brake booster and see how that works. I can guarantee it's not the tune. Do your other steering wheel buttons work? Radio volume, etc and just the cruise doesn't work? If so, I can almost assure you it's the sensor on the brake booster.

    When I had my H&S tuner installed I always ran on HD300 and hot. That's where mine got the best mileage. I could get around 16 mpg hand calculated. Remember these tunes were not written for mileage but rather horse power.

    For trans tuning I tried all of them. There is S1L, S1M, S1H, S2L, M & H. The schedule 1 tunes lock the torque converter in 4th and 5th. The schedule 2 tunes only lock it in 5th. The L setting goes into 5th TC lock around 45, M around 55, and H around 65. That's for both schedule tunes. I ran mine on S1M all the time.

    The tire setting is not really the size on the tire. I run 35 X 12.50 X 20. Setting it to 35 was way off. Here's the recommended way to get pretty close. Park on a hard surface (driveway, parking lot, etc) and place a flat board on top of your tire. I always use one of the rear tires. They take a tape measure and measure from the hard surface to the bottom of the board. If I remember correctly mine was set to 33.25. Speedo was spot on.

    Set defuels to:

    Boost set at 48
    Cold coolant set at 160
    Hot coolant set at 220
    Engine oil temp set at 220
    Trans temp set at 220
    Pyro 1 set at 1450
    Pyro 2 set at OFF
  • Oh and here is the part number for the cruise control switch: 3L3Z-9F924-AB. Here's a video showing where it's at;
  • edited June 2019
    Thanks for the advice and Video. I am going to check that out. I'm going to keep it on HD300 and hot. I changed all the settings to ones you posted. Only thing I need to do now is run the installer again and reset tire size and transmission tune. Does the tune get better the more I drive it? Thanks again.
  • Yes the tune will "settle in" as I call it. You will see more power and possibly better fuel mileage once the truck learns your driving habits. The transmission has what's called adaptive memory where it learns your driving habits. Takes about 500 miles or so to "learn". You might get hard shifting, and things like that during that time. There is a procedure to help speed that up. From the manual:

    Transmission Relearn
    The 5R110 automatic transmission on the 2008 - 2010 6.4L Powerstroke has what is called
    Adaptive Memory and is constantly learning and adapting to different horsepower levels,
    temperatures, driving habits, etc. After completing the Install Download process on the 6.4L
    Powerstroke, the Transmission Adaptive Memory is automatically reset. We highly recommend
    performing a Transmission Relearn procedure after installing H&S tuning to help the
    transmission perform correctly with the added horsepower. The 5R110 automatic transmission
    will eventually learn over time on its own, but the relearn procedure gives a good
    baseline for the adaptive learning and helps to speed up the learning process. To perform
    the relearn procedure, please follow these instructions:
    When re-training the transmission, ALWAYS follow posted speed limits. Do NOT attempt
    runs in adverse weather conditions such as snow, ice, rain, wind, or any other
    conditions that may affect your vehicles traction or impair your visibility!
    After H&S tuning is installed, perform each of the following 0-80 MPH runs while in the
    Performance power level. During this relearn process, you may experience hesitation
    during shifts, hard shifts, or defuel patterns, all of which are normal:
    • 0-80 MPH @ 25% throttle position, then slow down and come to a complete stop.
    • 0-80 MPH @ 50% throttle position, then slow down and come to a complete stop.
    • 0-80 MPH @ 100% throttle position, then slow down and come to a complete stop.
    The Transmission Relearn procedure is complete.

    Here's a copy of the manual should you want to review: There are two sections for the 6.4. Look starting on page 37 for some settings and 53 for others. You can also see other options in the beginning of the manual for tuner set up.
  • Thanks again for your help! I'll post when the tune settles in and I fix the cruise issue.
  • Update, I've tried mild and hd300 on 0 lbf and am getting worse fuel economy. I have to get a new starter possibly after they tested the alternator and it keeps passing the test.

    Smokin, which lbf setting did you run?
  • I ran LBF 3 (default)
  • Thanks. I'll try that when I tune it again
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