MM3 Tuner Troubleshooting Guide

MM3 Power Tuner Trouble Shooting Guide

*Please Read Thoroughly Before Contacting Us For Technical Support!*

ECM Write Errors (aka failed flash):

  • Make sure your batteries are fully charged and hold at least 12V before programming. 12.3 to 12.5V is preferred. Low voltage is the most common issue that causes a failed programming attempt.
  • Make sure all tuner connections are connected properly. This includes the J1939 unlock cable. The unlock cable must be plugged in all year models we service in order for the MM3 to function. Often error code 15210 shows up with the unlock cable is not making a connection.
  • Make sure there is only the tuner plugged into the OBD port. Many guys run AMP Power Steps or other devices that use the OBD port. These devices cannot be plugged into the OBD port or hard-wired to the OBD connections, even with a pass thru OBD Splitter.  Failure to do so will cause a failed write to the ECM and potentially a damaged (aka “bricked”) ECM.

If a failed ECM write occurs, often times the tuner will automatically try to program the truck back to stock software as a safety. If this happens let the tuner do its thing. Once that occurs, please check the above and try writing the ECM again.

If the above does not work and you are left with a truck that does not start and the dash flashes every warning light possible, then it is time to try a hard ECM reset. To do so, disconnect the tuner from the OBD port first. Then disconnect both truck batteries. Charge both batteries for about 10 minutes with a charger. Then reconnect the batteries and then plug the tuner back in last. Then try writing the ECM again. If this fails also, the contact us for technical support as it may require a special recovery file from MM3 Power to restore your truck’s ECM.

Tuner Communication Issues:

  • If your tuner suddenly acts like it was never installed on the truck (after already programming the ECM for the first time), meaning you no longer see your RT menu, ABS menu, and/or the disclaimer message pops up when you start the truck… there is good chance your tuner is not communicating with the ECM. This is usually indicated on the tuner by noticing the “ECM icon” (tiny computer chip picture) at the bottom right-hand corner of the main menu. If this icon is blue or red, that means the tuner is not talking with the ECM. It should be green if all is plugged in correctly and the truck is running. Poor connections or weak batteries often cause this condition.

If you suspect the problem above, try unplugging the tuner’s main plug at the OBD port and plugging it right back in. This resets the tuner. This may fix it. If still no good, check the micro USB cable that runs from the tuner’s display to the main unit for a loose connection. Then do another tuner reset. See if this fixes the issue. IF NOT, Then do a hard ECM reset. To do a hard ECM reset, unplug the tuner first and then disconnect the truck batteries. Charge the truck batteries for about 10 minutes with a charger. Then reconnect the batteries first and then plug the tuner back in last. See if this fixes the issue. If NOT, contact us for support.

SD Card Issues:

  • Sometimes due to poor connections or low battery voltage, the SD Card errors can occur. For example, your tuner worked fine one day and the next your start up the truck and you get a message stating no valid SD card detected.

If you experience this issue, first unplug the tuner from the OBD port. Then remove the SD card and reinsert it. Make sure it is facing correctly and properly seated. Then reconnect the tuner at the OBD port. See if this fixes the issue. IF NOT, you may have to reformat your SD card and then have to download, unzip, and paste the MM3 firmware files available off the MM3 Power website. Then you would do a repaste of your tune files from us back on the tuner’s SD card.

How to Reformat

How to reload/update the firmware files


  • If you perform an operation on your SD card such as updating firmware files or adding tune files and then you get an error message when you replace the card in the tuner that states “invalid SD card…” then most likely you made a mistake pasting the files on the card. Files have to be placed correctly on the card or the tuner will not read it. Nothing we can tell you to do here than go back and recheck your work. If you still have issues, then contact us and please and send us pictures of how the files look on your computer’s screen so that we can advise.
  • If you pasted tune files from us on your SD card and you cannot find them on your tuner via the ECM or RT menus…then most likely there is a file name error. Make sure file names have not been renamed by you or your computer. File names cannot exceed 8 characters.

Don’t unplug your MAP Sensor!:

  • The only tuning we sell now that requires anything to be unplugged under the hood is our 2010-2012 year model truck tuning. On these trucks, the throttle valve must be unplugged. Guys often mistake the throttle valve for the MAP sensor.  The MAP sensor must stay plugged in on all trucks. Obviously, some customers do unplug EGR components under the hood, and if your tuning supports that…by all means do that but still do not mistakenly unplug the MAP sensor.

Check Engine Light:

  • If you get a CEL or service message, do not freak out! Often Check Engine Lights and service messages are harmless. Often times they are easily cleared.
  • If you get a check engine light, you can use your tuner to attempt to clear it. To do so, turn the ignition on/run, but do not start the engine. Then go to the ECM menu on your tuner. Select “ECM tuning and DTC”.  Then select “DTC”.  Then read codes.  Then clear them.  Then restart the truck. If the codes pop back up again, use your tuner to read the codes again and send us a picture of that to examine.
  • If you get a perform service message and you have no DTCs, then you most likely have something that needs a dealer’s attention.

Accelerator Pedal Quits Working:

  • Due to the nature of the operating systems on 2013, 2014, and 2015 models trucks, these trucks can lose the function of the accelerator pedal if the owner makes certain mistakes. However, if this happens, do not panic. It can be easily corrected. To correct this, either do one of two things…either disconnect both battery cables and reconnect OR program the custom file to the ECM again.
  • To avoid the accelerator pedal shutdown…Wait at least one minute after startup before you program in an RT tune. Do not set the RT configuration to “every key on”. Do not leave the ignition switched to “Run” for an extended period of time (5 minutes or longer) without the engine running.
  • Avoid these things and there won’t be any issues.
  • 2010-12 and 2016-18 Model Trucks do not have the accelerator pedal shutdown issue.

How To Adjust Your Speedometer Calibration With The MM3 Tuner:

  • Suppose you equip your truck with tires taller or shorter than stock and it messes up the calibration of your speedometer. Good news, you can easily adjust your speedometer’s calibration with the tuner. First turn your ignition to “run” but do not start the engine. Then simply go to the main menu and select the “ECM Tuning/DTC” menu option. Next, select the “ABS” menu option. Next, enter a tire size and program it in. Now road test!
  • Please keep in mind that the tire size you enter for correctly reading speedometer may not line up the actual tire size you have on your truck. For example, you may have 37-inch tires on your truck but you may end up programming a tire size of 36.2 or 37.6 (just examples) to get the speedometer correctly reading. Also please never make a tire size adjustment with your tuner with the engine running! If you do, you can wipe out your ABS modules memory.
  • If by chance you make the mistake and wipe out your ABS module’s memory (this will be noted by a CEL, ABS Warning light, and Speedometer that does not register at all)… do not panic as it can be easily fixed. To fix this condition, simply program the tire size in again as described above and it should restore your ABS Module.

MM3 EGT Sensor Not Reading:

Whenever you install your new EGT Sensor for the MM3 tuner you must first reset the tuner in order for it to read the sensor. So if you search through the temperature menu and cannot find the MM3 EGT sensor, do this…Unplug the tuner from the OBD port and plug it back it back. Then touch any gauge in a dashboard layout to bring up a menu option for that gauge. Scroll and select “temperature”. Then scroll and select “MM3 EGT Sensor”. Set your range and alarm preferences if you desire and exit out. The EGT should now display provided the EGT Sensor is installed and work properly.

General Concerns That Are Not Concerns:

  • Please understand that when you tune and modify your truck things will be different. Please give your tune some time to settle in on both you and the truck. Automatic transmissions have to relearn and this can take a few hundred miles after programming. Automatics may be a bit slushy and mushy until they relearn. Once an automatic relearns, the shifts may be a bit more aggressive and firmer.
  • Diesel engines can produce smoke and produce a strong exhaust odor if emissions are removed…so if you do that, be prepared. Also, the customer must realize running a deleted diesel on the highway can break laws and not pass inspection. So if you get a ticket or can’t pass inspection, that is the customer’s problem, not ours.

We hope this guide helps and we will add more to it in the future as we find more common issues that need addressing.

Still having issues? Then please contact us by clicking here for technical support.

Thank you and God bless!
Double R Diesel