Reading Xbox One POST Codes

Xbox One POST codes are the console's boot progress markers. When a board powers on but does not finish booting, the POST bus can tell you where it stopped so you are not guessing blindly.

What POST Codes Are

During startup, the Xbox Southbridge steps through many hardware checks. A POST reader listens to the console's I2C POST bus and prints the current hexadecimal code. If the console hangs, the last code is your clue for the area to inspect next.

For Xbox One, the open-source PicoDurangoPOST project turns a Raspberry Pi Pico into a POST-code monitor. The project supports Xbox One Phat, Xbox One S, and Xbox One X through the FACET connector, and Xbox Series S/X through AARDVARK.

What You Need

• Raspberry Pi Pico or Pico 2
• PicoDurangoPOST UF2 firmware from the project's latest release
• Thin wire for SDA, SCL, and GND
• USB serial monitor software, or XboxPostcodeMonitor
• Coolshrimp's browser POST code lookup tool: Xbox POST Code Web Tool

Flash the Firmware

The Pico needs the PicoDurangoPOST firmware before it can read anything. This quick guide is also built right into the web tool under Flash Firmware, with direct firmware downloads.

Step 1 — Enter bootloader mode

1. Disconnect the Pico from your computer.
2. Hold down the BOOTSEL button on the Pico.
3. While holding BOOTSEL, connect the Pico via USB.
4. Release the BOOTSEL button.
5. The Pico appears as a USB drive named RPI-RP2.

Step 2 — Copy the firmware

Download the correct .uf2 file from the latest PicoDurangoPOST release (or straight from the web tool), then drag & drop it onto the RPI-RP2 drive:

• durango_post_monitor.uf2 — Raspberry Pi Pico (RP2040)
• durango_post_monitor_pico2.uf2 — Raspberry Pi Pico 2 (RP2350)

Wire the Pico to the Console

Connect the Pico to the console's POST debug points (the web tool's Wiring Guide popup carries the same reference):

• SDA: Pico pin 1 (GP0) → console pin 26 (pin 3 on Series S/X)
• SCL: Pico pin 2 (GP1) → console pin 25 (pin 1 on Series S/X)
• GND: Pico GND → Xbox GND

Where to tap the POST bus on every board revision — Xbox One OG & S, One X, Series S and Series X — and the matching Pico pins (I2C DAT, I2C CLK, GND).

Read the Output

1. Connect the Pico to your computer by USB and open the serial port at 115200 baud (or use XboxPostcodeMonitor).
2. Apply standby power to the console. The Southbridge needs standby power before any POST data can appear.
3. Power the console and watch the serial output. The reader starts in POST monitoring mode automatically.

Using the Coolshrimp Web Code Tool

Once the Pico gives you a code, open the web tool and enter the POST value exactly as shown. The tool is handy because it works in the browser and keeps the code lookup beside your serial monitor.

Open Xbox POST Code Web Tool

1. Copy the last repeated POST code from your serial monitor.
2. Paste or type it into the web tool.
3. Read the matching stage/error note, then compare that with the console's symptoms.
4. If the code changes each attempt, record the sequence. The last stable code is usually the most useful clue.

Reading the Results

A POST code is not a magic "replace this chip" answer. Treat it as a direction: power rails, storage, RAM, Southbridge, APU, firmware, or a communication path. The best workflow is to combine the code with measurements and visible symptoms.

• Stops instantly: verify standby rails, shorts, and basic power sequencing.
• Progresses then hangs: lookup the last code and inspect that boot stage.
• No serial data: confirm FACET orientation, SDA/SCL continuity, GND, and standby power.
• Random codes: check soldering, noisy connections, unstable power, or board damage.

Reference

This guide is based on the PicoDurangoPOST project documentation. The project notes that firmware v0.3.0 removed some older name-display behavior in favor of XboxPostcodeMonitor, but the Pico still monitors the POST bus and prints codes over USB serial.