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Decoding POST Error Codes

I'm curious about error warnings and numbers such as: 1xx 161 164 2xx 3xx 4xx 5xx 6xx 17xx. What do they mean?Celeste Stewart

What are these Error Codes?

The error codes you just listed are POST error codes. POST stands for Power On Self Test. Each time your computer boots up, its BIOS runs a series of tests to ensure that everything is working as it should. When all is well, Windows then loads. When all is not well, error codes are generated and you may hear a series of beeps. Because different BIOS manufacturers often have their own unique codes, it's important to double-check with the manufacturer to ensure that you are comparing your computer's POST test results with the correct codes.  

IBM POST Error Codes

The codes that you describe match the original IBM's POST error codes. IBM used a series of numbers such as1xx, 2xx, 3xx, 4xx, 5xx, 6xx, 7xx, 8xx, 9xx, and 10xx. Each leading number represents a category. For example 1xx indicates a "system motherboard error" with error 161 indicating a "CMOS battery failure" and 164 indicating a "memory system size error." Likewise, error 17xx points to hard drive problems with specific errors listed as 1701, 1702, 1791, etc.

The Major IMB POST Error Code Categories

With literally thousands of codes, we won't go into all of them. However, below are some of the more common categories:

1xx - System motherboard error

2xx - Memory failure

3xx - Keyboard failure

4xx - Monochrome display adapter failure (video card error codes)

5xx - Color/graphics display adapter failure

6xx - Floppy drive

7xx - Math co-processor

9xx - Parallel Printer port

10xx - Second parallel printer port error

11xx - Serial Port error

12xx - Second serial port error

13xx - Game port adapter

14xx - Printer control

15xx - SDLC adapter

16xx - Display emulator cards

17xx - Hard Drive

18xx - I/O card error

19xx - 3270 card errors

20xx - Bisynchronous Communication Adapter (BCA)

30xx & 31xx - Network card/LAN Adapter error

48xx & 49xx - Internal modem

74xx - VGA card

104xxx - ESDI hard drive error

Decoding the BIOS Beeps

What about those mysterious beeps? Again, the beep codes do vary by manufacturer, but the following should give you a pretty good idea as far as what's wrong:

  • Short and steady beeps often indicate that the power supply is failing
  • Long and steady beeps usually confirm that the power supply has failed
  • A long, continuous beep points to memory failure
  • One long beep followed by two short beeps indicates a video card failure
  • No beep at all can indicate a bad power supply, a bad beeper, or the computer is not plugged in or turned on.

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2 Responses to “Decoding POST Error Codes”

  1. 001   colin

    could you please tell me how to repair error codes 1xx 161 164 2xx 3xx 4xx 5xx 6xx 17xx thank you regards colin

  2. 002   Celeste Stewart

    Hello, here's some information that should help:
    Thanks! The Team
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