# Non-functioning onboard LED **URL:** \ **Category:** Nano R4\ **Created:** [September 9, 2025, 9:12pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856 "2025-09-09T21:12:40Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![sharp5](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/sharp5/32/1126810_2.png) [@sharp5](https://forum.arduino.cc/u/sharp5)\ **Post date:** [September 9, 2025, 9:12pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/1 "2025-09-09T21:12:40Z")
Got a brand new Nano R4 today and cannot get the onboard orange LED to work. Tried the blink sketch to no avail. RGB LED works fine. The only other R4 board I have is a Minima which I received during the beta program. Cross-referencing the schematic with the core source code, LED\_BUILTIN resolves to digital pin 22, which is pin P204 on the chip. So that’s correct. Maybe I just got a bad one. Not a problem as I have no real need for it but I just wanted to make sure I’m not going mad. It would be handy to indicate bootloader mode though. ---
**Author:** ![UKHeliBob](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/ukhelibob/32/215663_2.png) [@UKHeliBob](https://forum.arduino.cc/u/UKHeliBob)\ **Post date:** [September 9, 2025, 9:18pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/2 "2025-09-09T21:18:28Z")
Do you have any external circuit connected to the board ? ---
**Author:** ![sharp5](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/sharp5/32/1126810_2.png) [@sharp5](https://forum.arduino.cc/u/sharp5)\ **Post date:** [September 9, 2025, 10:37pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/3 "2025-09-09T22:37:50Z")
Nope. It’s just dangling from a USB cable connected to my laptop. ---
**Author:** ![david\_2018](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/david_2018/32/1013044_2.png) [@david\_2018](https://forum.arduino.cc/u/david_2018)\ **Post date:** [September 9, 2025, 10:43pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/4 "2025-09-09T22:43:10Z")
Can you get to the LED with a voltmeter to measure the voltage? Could be a bad LED, bad resistor, bad thru-hole connection on the board, etc. ---
**Author:** ![anon85221860](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@anon85221860](https://forum.arduino.cc/u/anon85221860)\ **Post date:** [September 10, 2025, 2:27am UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/5 "2025-09-10T02:27:14Z")
The single color and RGB are mentioned in section 2.8 (pg 7 of 20) The RGB shows up as "DL1" in the table, pg 14 of 20, but no further mentions of the single color ('P204'). For some reason they didn't associate it with "D13", I guess. [https://docs.arduino.cc/resources/datasheets/ABX00142-datasheet.pdf](https://docs.arduino.cc/resources/datasheets/ABX00142-datasheet.pdf) ---
**Author:** ![ptillisch](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@ptillisch](https://forum.arduino.cc/u/ptillisch)\ **Post date:** [September 10, 2025, 1:01pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/6 "2025-09-10T13:01:37Z")
> [@anon85221860](#): > > For some reason they didn't associate it with "D13" Since the Renesas RA4M1 microcontroller has more I/O pins than the number of I/O pins on the Nano's headers, it was possible to use a dedicated pin for the built-in LED. Doing that allows the LED to be used without having to give up using pin 13 for other purposes. This is especially useful when you consider that pin 13 is the SCK pin of the SPI bus, and thus often in use. ---
**Author:** ![anon85221860](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@anon85221860](https://forum.arduino.cc/u/anon85221860)\ **Post date:** [September 11, 2025, 2:00pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/7 "2025-09-11T14:00:30Z")
I opened my Nano R4. (FWIW - I don't like the new box style). Where is "22" mentioned in the write-up? It was mentioned by the OP. The on-board (built-in) LED blinks both ways -- ```arduino void setup() { pinMode(LED_BUILTIN, OUTPUT); } void loop() { digitalWrite(LED_BUILTIN, HIGH); delay(500); digitalWrite(LED_BUILTIN,LOW); delay(2000); } ``` ```arduino void setup() { pinMode(22, OUTPUT); } void loop() { digitalWrite(22, HIGH); delay(500); digitalWrite(22, LOW); delay(2000); } ``` It transitions dim - bright - dim -... during the upload. ---
**Author:** ![sharp5](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/sharp5/32/1126810_2.png) [@sharp5](https://forum.arduino.cc/u/sharp5)\ **Post date:** [September 11, 2025, 3:51pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/8 "2025-09-11T15:51:37Z")
`Serial.println(LED_BUILTIN);` 22 I guess mine must have failed. It’s difficult to test during assembly unless you can integrate the process with a camera to detect the LED illumination. ---
**Author:** ![ptillisch](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@ptillisch](https://forum.arduino.cc/u/ptillisch)\ **Post date:** [September 11, 2025, 4:04pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/9 "2025-09-11T16:04:01Z")
> [@anon85221860](#): > > Where is "22" mentioned in the write-up? It was mentioned by the OP. @sharp5 said they found the pin mapping in the source code. You can see it here: > (the Arduino pin number is the index of the `g_pin_cfg` array) The `LED_BUILTIN` macro is defined here: > ---
**Author:** ![david\_2018](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/david_2018/32/1013044_2.png) [@david\_2018](https://forum.arduino.cc/u/david_2018)\ **Post date:** [September 11, 2025, 4:34pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/10 "2025-09-11T16:34:16Z")
You could also just print LED\_BUILTIN to the serial monitor to see the PIN number. ---
**Author:** ![ptillisch](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@ptillisch](https://forum.arduino.cc/u/ptillisch)\ **Post date:** [September 11, 2025, 4:44pm UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/11 "2025-09-11T16:44:31Z")
If you are using Arduino IDE 2.x, you can also just hover the mouse pointer over a reference in the sketch. The IDE will then show you the value. Likewise, you can right click on it, then select "Go to definition" from the context menu to open the file containing the definition in a tab in the Arduino IDE editor. ---
**Author:** ![jorgetrujilloroman](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jorgetrujilloroman/32/1007828_2.png) [@jorgetrujilloroman](https://forum.arduino.cc/u/jorgetrujilloroman)\ **Post date:** [September 16, 2025, 9:20am UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/12 "2025-09-16T09:20:32Z")
Hello sharp5, Could you please let me know if the onboard LED works when running the **Blink** example: `IDE > File > Examples > 01.Basics > Blink`? Also, the onboard LED should light up during sketch upload. If it still doesn’t work, you can contact support directly via the form at [https://www.arduino.cc/en/contact-us/](https://www.arduino.cc/en/contact-us/). Best regards, ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [March 15, 2026, 9:21am UTC](https://forum.arduino.cc/t/non-functioning-onboard-led/1405856/13 "2026-03-15T09:21:07Z")
Closed on March 15, 2026, 9:21am UTC This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.