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FixGameTech

PlayStation 4 • Troubleshooting / Diagnostics

PS4 UART Fault Finding

A technical reference for PlayStation 4, PlayStation 4 Slim and PlayStation 4 Pro UART diagnostics, NOR preparation, connection points and common UART fault patterns.

PS4UARTNORDiagnosticsBoard RepairMedium

Overview

UART can provide boot and diagnostic information from a powered PlayStation 4. On an unmodified NOR, the serial console may only show blank spacing; the UART flag must be enabled in the NOR image before useful output is available. This is especially helpful when diagnosing consoles that remain on a pulsing blue light.

PlayStation 4PlayStation 4 SlimPlayStation 4 ProDifficulty: Medium

Required Equipment

3.3V TTL

  • 3.3V USB-to-TTL / UART reader; a CH341A may also be used depending on setup.
  • NOR programmer.
  • WSON8 adapter for CUH-12XX / Slim / Pro NOR packages.
  • 16-pin SOP adapter for CUH-10XX / CUH-11XX.
  • Soldering iron or hot-air station.
  • 3.3V bench supply when working with an in-circuit method.
  • Software compatible with the selected NOR programmer.
  • PS4 Wee Tools for dump validation, UART flag changes and terminal access.
  • Keep multiple verified backups of the original NOR before writing any modified image.
Voltage matters: use a 3.3V UART level. Do not connect a 5V TTL signal to the console.

Prepare the NOR for UART

  1. Read the NOR at least twice.
  2. Compare the dumps and confirm they are identical before continuing.
  3. Run the base validation / entropy check in PS4 Wee Tools.
  4. Keep untouched copies of the original dump in a separate location.
  5. Enable the UART flag in PS4 Wee Tools and verify that the NOR information reports UART as enabled.
  6. Write the verified modified dump back to the NOR.
  7. If the chip was removed, solder it back to the motherboard before UART testing.
The NOR contains console-specific information. A bad read or lost original dump can leave the console unrecoverable, so backup verification is a critical step.

PS4 Fat / Slim / Pro UART Pinout

BWE Reference

Click the image to open the full-size zoom viewer.
Use the annotated board revision that matches the console. The reference identifies UART TX/RX and ground locations for the supported PS4 motherboard families.
Pinout reference image: Better Way Electronics (BWE), provided for this FixGameTech technical reference.

Terminal Settings

Baud rate 115200
Data bits 8
Parity None
Stop bits 1
Flow control None

After connecting the reader to the computer, PS4 Wee Tools can be used through its UART terminal option. Power the console on only after the wiring and voltage level have been checked.

Common UART Fault Patterns

DCT block errors

A DCT disabled error points toward communication trouble in a RAM block. A block contains two RAM devices, but replacing RAM alone may not solve the fault if the underlying issue is an APU-to-RAM connection problem.

Typical RAM block pairs are 0/1, 2/3, 4/5 and 6/7.

loadBios / sceSblSlLoadSelf errors

These can indicate that SYSCON is not successfully decrypting CoreOS. Possible causes described in the source include RAM faults or CoreOS corruption. Memory-test and firmware-slot work should only be attempted with verified backups and the proper tooling.

SAMU enter/leave loop

If UART repeatedly cycles through SAMU enter/leave messages, the source associates this with a likely APU-related problem.

Other examples

Repair Wiki also documents an EAP-key panic that may be recoverable with PS4 Wee Tools, an IDPS error with no documented fix there, and a timer/WDT last-message case associated with a failed crystal oscillator.

Safety & Data Integrity

Do not experiment on the only copy of a NOR dump. Verify repeatable reads, preserve originals, confirm the exact board revision and use 3.3V logic before making any UART connection.
PS5 UART PinoutsBack to Tools

Technical basis: Repair Wiki, “Playstation 4 Fault finding with UART.” This FixGameTech page reorganizes and paraphrases the source for a cleaner technical reference.