What do the AFM Disabler lights mean?

Posted by Robert McJannett on

What is the difference between the colours?

Nothing. It is purely decorative, there is no functional difference. When it is plugged in it will light up your footwell. In our opinion the Red model is the least annoying on the eyes. Some people have put electrical tape over it.



What do the AFM lights mean? Will I see V4 Mode?

Being a DISABLER, by definition, you will NOT see V4 Mode.

On the latest AFM DISABLER Modules, the four blue lights are basically to indicate the unit is operating. They will go out when the vehicle is not running as described below (Power Saving). The lights are as follows:


  • LED #1 - Power is ON and unit is AWAKE and vehicle is ready for commands
  • LED #2 - RPM > 500 and Engine is Running (not cranking or stalled)
  • LED #3 - Vehicle V8 mode is legal (no engine damaging DTCs present or other parameters out of spec)
  • LED #4 - In active command mode and controlling the AFM



When you first plug the module into the OBD2 port, you may see the LED cycle in a pattern (units produced after Sept. 22rd 2014) which is just an indication that it is performing internal hardware diagnostic checks before going into full operating mode. Earlier modules may not cycle the LEDs (but still perform the hardware checks in "silent" mode).

During operation, it is normal to see the lights cycle and go on/off in different sequences sometimes appearing to dim or vary in brightness (or even almost go dark). The lights are not really useful to you as the driver, but are used more for diagnostic or status indications when doing troubleshooting/verification. You will see the lights dim dramatically as you slow down/brake. As long as the vehicle is staying in V8 the unit is operating normally.



Do the lights ever go out?

Yes, the units have a "SLEEP" mode where after you shut the key off and/or the engine is not running. All the LIGHTS WILL GO OUT and it will go into power saving mode.

This power saving mode is EXTREMELY low powered and on a normal capacity battery in normal temperatures (i.e. ~70 degrees F) it should not affect normal battery voltage/charge for at least a couple of weeks (and probably much longer). The maximum draw in sleep mode is 6mA (and is nominally about 2-3mA).

The device will wake up again when you start the engine and the LEDs may cycle 2-3 times as the unit performs internal diagnostics. Earlier versions may not cycle the LEDs.

It may take up to 20 seconds (usually less) for it to start showing lights again ... this is NORMAL because it may take that long before we can send commands to the vehicle (especially on a cold motor).



Is it normal to have just one LED lit?

I ask because every picture I've seen has all the lights lit and mine only has the far right lit. The lights cycled left to right on initial start up and just the far right stays lit. I havent seen 4v mode since I plugged it in so it appears to be doing its job. Just concerned if the lack of lights is pointing to a failure down the road.

As long as one light is on and the device is working then that is fine. The light pattern will vary depending on how it needs to communicate with the vehicle. If the customer does notice that it starts to go back to 4 cylinder mode then we can have it sent in to be inspected.



Range Technology AFM/DFM Disabler for GM Vehicles in Canada from Performance Improvements

The AFM/DFM Disabler is inexpensive and requires no time or effort by the owner to be installed. There is no learning curve or homework required.

Plug in the device, wait for the LED’s to power on, start your vehicle and drive.

It’s truly a plug and play resolution to potentially very costly repairs.


Other AFM Disabler Articles

Share this post

← Older Post Newer Post →