The RX8 Cluster Commander is a circuit used to translate the GM canbus data stream (commonly referred to as GMLAN) to the Mazda instrument cluster. It uses two separate canbus interfaces to translate the data between the two. The interface that's connected to the GM side only listens, meaning that you can perform ECM reflashes via HP Tuners or EFI Live without needing to disconnect the Cluster Commander from the network. 

The cluster commander has full control of the Tachometer, Odometer, Speedometer, Check Engine light, Oil and Coolant gauges. There are a few limitations to be aware of with the OEM gauge cluster.

OEM Limitations

  • Oil pressure gauge is faux-analog. Though it moves based upon RPM and Coolant temp, the input is an on/off signal. 
  • Coolant gauge is similarly faux-analog. It has a Low/Medium/High setting, and is very slow to move.
  • TCS, DCS, TPMS, Security Warning Lights are disabled.


  • Updateable Firmware - Any bugs that show up can be fixed with a reflash.
  • Speedometer fine tuning - Speed is read via the GM ECM, and can be adjusted without needing HPTuners or EFI Live.
  • Odometer fine tuning - Similarly, can improve odometer accuracy without needing a ECM reflash.
  • Voltage Monitoring - Will turn on the Battery Lamp if voltage is below a threshold fore more than 3 seconds (Default: 12.6v)
  • Check Engine Light Functionality - Reads the GM's MIL lamp wire and illuminates the Check Engine light on the cluster.
  • Oil pressure table - User editable truth table with 500 RPM resolution to make sure your oil pressure is good everywhere.
  • Coolant table - User settable Low/Medium/High ranges (Default: 160°F and 220°F).


The most convenient place to install the cluster commander is behind the cluster itself. To gain access, you'll need to remove the steering column trim (3 screws from the bottom side), then remove the gauge hood (held in place by 4 plastic pins - be careful to lift directly upwards). The instrument cluster is held in place with 3 screws and a clip that holds the wiring in place. To free the harness, twist the clip 90 degrees and then remove the 2 connectors from the rear of the cluster. A disassembly diagram can be found online. You'll need to run 3 wires from the GM ECM to this location two for CAN and one for the check engine lamp. 

There are two connectors on the back of the cluster - a large one and a smaller one. On the smaller one, strip back a few inches the harness tape to expose the wires - we won't be tapping any of the wires from the larger connector. We're looking for 5 wires in the small harness.



CC Harness Function Pin Wire Color
Red Switched 12v 1G Black/Yellow
White MIL Input From ECM Brown/White
Green No Connection * *
Blue CANBus High 1J Blue
Brown CANBus Low 1L Green/Black
Yellow GM CANBus High From ECM Tan/Black
Gray GM CANBus Low From ECM Tan
Black Ground 1E Black

Three of the wires - Oil Pressure, CAN High and CAN Low are going to be cut and spliced into the circuit. Cut the wire far enough away from the connector leave enough space to comfortably fit a crimper. Power and Ground (1A and 1G) will be tapped and spliced to provide power to the circuit. If you're using a butt splice, cut, strip and twist the wires together into one side of the crimp to tap. 

There are 8 wires to connect - A pair of CAN wires for the Mazda and GM side (each), the oil pressure switch to the instrument cluster, and the Malfunction Indication Lamp (MIL/Check Engine) from the ECM. GM Canbus wires can be taken from the OBDII Port (if already wired to inside the cabin). The MIL lamp wire will need to be extended to the dash, check your wiring documentation for details.

  • Red - 12V connected to switched power, like 1G above.
  • White - MIL lamp input.
  • Green - Oil Gauge output - to 1H (Light Green).
  • Blue - Mazda Canbus High - to 1J (Lavender).
  • Brown - Mazda Canbus Low - to 1L (Green/Black).
  • Yellow - GM Canbus High to the ECM - Tan with a Black stripe. Usually twisted around the Low wire.
  • Gray - GM Canbus Low to the ECM - Tan. Usually twisted around the High wire.
  • Black - Connect to 1A on the instrument cluster.

The circuit enclosure box is built with handles that make it easily zip-tied out of the way behind the gauge hood. It's recommended to leave the gauge hood and column trim off until everything appears to be working.


Scotchlock vs. Crimp vs. Solder in automotive applications is a long debated topic. In my own experience I will say that I prefer a good crimp over a crappy solder, and shame upon anyone that strips and twists wires together with electrical tape. Since the wires in the OEM cluster are thin 22awg wires, I've begun including 3M Scotchlock connectors in the kit to help connecting the box into the wiring. CANbus is very resilient to noise and forgiving in an automotive environment. 

Software Setup

Cluster Commander doesn't require any additional setup to work - it's already populated with default values for that work well. The defaults are set for the LFX - the only major difference in settings from the LFX and the LSx engine is the oil pressure gauge.  (todo details). Assuming your Speedometer and Odometer settings from your ECM are good, no further setup is required.



Remove the two screws on the enclosure - this will expose the micro USB slot. (todo photos)

Serial Port Selection

The board uses the FTDI USB to Serial adapter for communication. This is a very common USB Serial converter that most operating systems have drivers built in for - but just in case, drivers can be installed from Once the driver is installed, the next step is to determine which COM port address has been assigned. To do this in windows - go to Control Panel - Device Manager - expand "Ports - COM & LPT" - and take note of any port numbers listed.

In this example the COM Port is 4. If there are multiple ports listed, disconnect the USB cable for 10 seconds and take note of which port disappears, then reconnect.

Serial terminal

Now that we know our COM port the next step is to install a Serial Terminal - if you're computer savvy, any terminal will do. PuTTY is free application that works extremely well. You can download it here. Once installed, open the application and select "Serial" - Change the Serial Line to the COM port noted above. Baud rate defaults to 9600. 




Most of the menus are straightforward (and options may change as the firmware evolves). Each letter surrounded by a parentheses is a menu option. If you are connecting to the circuit while the cluster is connected and powered you can manipulate the instrument cluster with the first section. The second section relates to settings that will need to be saved with the "(W)rite to EEPROM" option. Display VIN and Display Registers are used for troubleshooting purposes.

Oil Pressure

Different GM motors have different oil pressure requirements. We can view the Oil Pressure table. If the oil pressure is higher than the value listed then we simulate the oil pressure switch as closed and "good". Each value is good until the next RPM listed - so "0" is good until "500" rpm, and so on, until 7000 RPM. This gives us a better idea of oil pressure throughout the RPM range. The stock gauge has 4 "states" that tie into the engine temperature as well - so while the engine temperature is "cold" the oil pressure simulates higher than it does at "medium". If the engine is "hot" the oil pressure gauge barely moves at all - most likely to try and grab your attention. But lets be frank - the classic mechanical gauge has it's place for both reliability and information. 

Oil Floor

Almost all electrical sensors have "float" - a little bit of noise in the signal that prevents a static pressure from reading as truly 0 - either from ground offset, wire splicing, or sensor variance. To try and present the most accurate information possible we can subtract this static value from our oil pressure calculation. This is not completely necessary to do - it's often less than half a PSI of oil pressure difference.

With the engine off and cold, enter the Oil Pressure menu and press O and then D. The commander will display the oil pressure directly from the ECM for 5 seconds. Once you have this value, press E and enter it. This value will be subtracted from all oil pressure calculations.


The OEM cluster has 3 settings - Low, Medium and High. Here we can set the thresholds for each setting - although the stock temperature thresholds at 160 and 220 are fairly universal. GM engines tend to run a little hotter due to their reverse coolant flow and sensor location.

Speedometer Calibration

Changed rear tire size? Changed differential ratio after setting up your ECM? Using this menu will help reset your speedometer to be accurate. On a long flat stretch of highway with a good GPS, make note of what your GPS speed is and what your instrument cluster reports. Enter these values into the menu and a simple percentage adjustment will be applied across all incoming VSS speeds from the ECM.


This is a last-ditch option to get the speedometer working. Using a GPS as a speed source is generally inadvisable. A ECM-driven VSS will respond much quicker, won't have any problems locking on in bad weather, and doesn't care about terrain. Plus more advanced ECM's like the E39 there are a number of fueling options that depend on a valid VSS signal. 

Contact me for more details on how to connect a GPS to the circuit.

Updating Firmware

All units ship with the most recent firmware available. Download and extract the zip to a directory. With the board connected, click on "RunMe". A window will pop up and display the current com ports - select the one for the Cluster Commander and hit enter.


After hitting enter, the flash process will commence. If any errors occur during this process, let us know.

After completing, it's generally a good idea to connect to the Cluster Commander and doublecheck your saved settings. It may be necessary to Load the default values and re-enter your changes.



There are really only three ways for the circuit to fail - it cannot read the GM ECM, it can't output to the cluster, or the circuit itself is not receiving power. 

Status LED

The status LED is used to quickly verify communication between the ECM and the Cluster Commander without needing to hook up a computer. Communication from the instrument cluster to the Cluster Commander should be readily apparent - when powered, most of the error lamps will light up. With the cluster commander powered up the status LED with blink - this verifies that the cluster commander is receiving power. When the light turns solid it is receiving data from the GM ECM. 


With the laptop hooked up and menu system entered, you can hit the "V" key and after a few seconds the ECM will returned the VIN. If the ECM times out, try to pull the VIN again and verify the ECM is receiving power (key on, engine off). If the ECM still doesn't reply, double check your CANH and CANL wires with a multimeter, using a paperclip in the Cluster Commanders harness to the ECM Harness.


If there doesn't appear to be any communication with the GM ECM, the next step is to read the registers from the CAN interface. If the registers do not match the information below, contact me for additional troubleshooting steps or an RMA. <todo register output> 


I understand how easily a simple engine swap project that was only supposed to take 3 months working weekends can expand to a year or longer. If you have any issue with your purchase, contact me and we'll try and get something sorted out.


Openhoonage LLC make no representations or warranties of any type with respect to the contents in this manual. Openhoonage LLC disclaim any implied warranties or fitness for any particular purpose. Openhoonage LLC is not liable for any errors contained within or for incidental or consequential damages in connection with the supply, performance or use of the hardware and software or this manual. Openhoonage LLC reserve the right to revise this installation and user manual at any time, without obligation to notify any person of revisions.


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