CSP5 Switch

Our CSP5 switch has a replacement OBD II connector for a cleaner, stock-looking install. It is compatible with both MM3 and EFILive® (and depending upon the tuner EZ LYNK®). It currently covers 2006-2021 Cummins (for EFILive® 2018+ you will need our 2018-2022 Cummins Bypass Cable in order to flash the vehicle).

Helpful info: Our CSP5 switch has an orange/yellow LED light on the back and says "Fish Tuning" on the cable and circuit board. Our newest switch has five pins, not the four pictured below. Also, as long as the ECM has power, it will remember the last tune set even through key on-off cycles.

Please contact us at orders@fishtuning.com or (310) 499-0989 for more information.

Part Number: FTCSP5

And the short version for those extra clean installs using the supplied mounting bracket which places the switch just next to the OBDII port.

Part Number: FT CSP5 Short

All our CSP5 switches come with a small Ty-Wrap:

...Which allows you to add some strain relief to the cable helping to keep the cable from breaking or coming unplugged after installation.

Installing Your Cummins Switch


This CSP5 switch works with EFILive®, MM3, Smarty & RME tunes. Also supports HPtuners® L5P SOTF - requires bracket, not included.

As of this printing: For EFILive®, 06-09 trucks have five tunes. Later trucks have four tunes except 2010-2012 “cab and chassis” models which have two tunes. 2013+ is CSP4. If the switch only selects two or four tunes, then you likely have a CSP2 or CSP4 tune.

For MM3, Smarty and RME, all tunable years have five tunes.

Plug in the switch. It will start by blinking the firmware version number, a series of long and short blinks. Turn the key on and change the tune and it will blink the tune it just set.  Test all the positions, if it correctly blinks the tune number in each position, than it’s working perfectly. If it doesn’t work in position five or in positions 3-5, you most likely only have two or four tunes and should follow the directions for moving the tabbed washer. Once you’ve determined it’s working, you should finish installing it.

Unless you have a mounting bracket, installing the switch requires the drilling of two holes, one small and one large. If you don’t want to drill the second hole, you may cut off the anti-rotation pin so you don’t need the small hole.

After routing wire and before installing switch, please use included tie wrap to secure black jacket of the cable to the switch using the small slot in the corner of the PCB. This prevents wires from getting pulled out of the connector or the connector getting pulled free.

Your switch has a nut and two washers. The smooth washer must remain on the bottom with the tab located in hole number five*. If it falls out, turn the switch fully counter clockwise and place the washer back with the pin in hole number five. Make sure the switch moves exactly four clicks clockwise. If not, turn the switch back fully counterclockwise, move the pin, and try again.

*If you have a CSP2 or CSP4 tune, follow the instructions in the previous paragraph but place the tab in hole number two or four, instead of hole number five.

For 2018+ you will also need a Cummins Bypass Cable to flash (and to use the CSP5 switch). You MAY also need it for MM3, Smarty & RME if the security module fails.

HP Tuners L5P 6 position Tuning

Starting around 10/15/2021 all of the CSP5 switches we ship will also support HP Tuners® 6 position L5p tunes. The ones that have already been shipped out before that time may not yet have that capability (you can call us if you want more info on how to check). Where L is long and S is short, OS startup codes L-S-S or L-S-S-L support L5P and OS startup code L-S-L does not support L5P. You will need to move the tabbed washer to 6 to get 6 positions and you will need a bracket to adapt our CSP5 cable to work in a L5P. You may also need longer screws to mount the bracket in some years. We can supply those brackets or, you can print your own. We use ABS so it will stand up to the heat in the cab, but whatever you use, make sure it can survive through the hottest summer day. Here are .STL and .STP files of the bracket as it currently stands. It seems to work fine but the .STP file is included if you'd like to try and improve it.

L5P CSP5 Cable Adapter Bracket Files