An Introduction to Troubleshooting Your IBM PC
Capital PC User Group
The IBM PC family of computers (PC, Portable, XT and AT) comes
complete with built-in diagnostic procedures to assist a user in
identifying many problems that may occur with any of the computer's
components. These diagnostic procedures include:
1. A Power-On Self Test (POST) that is performed whenever a PC is
powered up or turned on.
2. General diagnostics testing that the user can perform using
the Diagnostics Diskette and accompanying Problem
Determination Procedures (PDPs) outlined in the Guide to
Operations manual for each system.
3. Optional advanced diagnostics testing that the user can
perform using the Advanced Diagnostics Diskette and procedures
provided in the Hardware, Maintenance and Service manual.
Power-On Self Test (POST)
Whenever you start up your computer, a series of tests are
automatically performed checking various components in your system.
This Power-On Self Test (POST) process provides error or warning
messages whenever a faulty component is encountered. Two types of
messages are provided: audio codes and display screen messages or
Audio codes consist of variations of sounds or beeps that identify the
faulty component. If your computer is functioning normally, you will
hear one short beep when the system is started up. If a problem is
detected, a different series of audio codes will be sounded. These
audio codes and corresponding problem areas are:
Audio Code Problem Area
No beep, continuous beep, or Power Supply
repeating short beeps
1 long beep and 1 short beep System Board
l long beep and 2 short beeps, or Monitor adapter card and/or
1 short beep and blank or monitor cable and/or display
1 short beep and either the Drive and/or drive adapter
red drive LED staying on or card
Personal Computer BASIC statement
On the XT and AT, the POST procedures also display system memory
as it is read. The last number displayed (640KB, for example) should
be the total amount of memory in your system, including system board
memory and any expansion memory.
During the POST procedures, error messages or numeric codes will be
displayed whenever a problem is detected. In most cases, the error
code will be a three or four digit number that, when checked against
the list provided in Table 1, will help identify the malfunctioning
General Diagnostics Testing
Each IBM computer comes with a Guide to Operations (GTO) manual; this
is the manual in the reddish-purple binder. The GTO includes a
Diagnostic diskette to assist you in identifying problems that your
computer may be having.
The Diagnostics diskette and corresponding Problem Determination
Procedures (PDPs) section of the GTO manual provide step-by-step
instructions to test the various parts of your computer system,
including the system unit with installed options, expansion unit,
keyboard, display, and printer. These tests should be performed when
you first install your system, at periodic times during the lifetime of
the system for precautionary purposes, and, of course, whenever errant
behavior is detected or suspected.
To run the diagnostics tests, place a backup copy of the Diagnostics
diskette in your A: drive and turn on your system or, if the system is
already on, press the CTRL, ALT, and DEL keys simultaneously to reboot
the system. The main diagnostics menu will be displayed with options
similar to the following:
0 - SYSTEM CHECKOUT
1 - FORMAT DISKETTE
2 - COPY DISKETTE
3 - PREPARE SYSTEM FOR MOVING
4 - SETUP [AT only]
9 - END DIAGNOSTICS
Options 0, 1, and 2 are part of the diagnostics procedures. Option 3,
"Prepare System For Moving", is used to "park" or secure the heads on a
hard disk so that the system unit can be safely moved without damaging
the disk or its contents; Option 4 is used with the AT to identify
installed options when you first set up your system.
Options 1 and 2 should be used whenever you want to check the operation
of your floppy diskette drives or to prepare a diskette for use,
without having to reload DOS, when performing the diagnostics
procedures. For general testing, however, you should select Option 0,
"System Checkout". When this option is selected, the system displays
a list of installed options for verification and then provides a
secondary menu of choices, similar to the following:
0 - RUN TESTS ONE TIME
1 - RUN TESTS MULTIPLE TIMES
2 - LOG UTILITIES
3 - END SYSTEM CHECKOUT
Both Option 0 and 1 walk you through a series of tests that check each
component in the system. During system testing, a three- or four-
digit error code will be generated for each component tested. If no
problem is found, the last two digits will be 00, for example 300, 900,
or 1700. Table 1 is a listing of many of the error codes that may be
generated during diagnostics testing.
If an error is detected when running Option 0, it is often advisable to
select the Log Utilities Option (2) to list any errors to disk or
printer, and then select Option 1, Run Tests Multiple Times. This will
help determine whether the problem is consistent or intermittent.
While the GTO diagnostics do an excellent job at identifying specific
problem areas or problem components, they provide limited assistance to
correct the source of the errors. In fact, the information most
frequently provided is to "Have your system unit [or problem device]
Advanced Diagnostics Testing
If you are the more adventuresome type, you can purchase the IBM
Hardware Maintenance and Service (HMS) manual for your particular unit
(prices are around $155). While the Guide to Operations manual is only
good for identifying a problem component, the HMS manual provides
information to both isolate and repair any failure of a "Field
Replaceable Unit (FRU)", that is, any part or component that has
interchangeable replacement parts that are stocked by IBM or the
Original Equipment Manufacturer (OEM).
The HMS includes an Advanced Diagnostics diskette and accompanying
Problem Isolation Codes (PICs) instructions to isolate and identify
problem components. To run the Advanced Diagnostics tests, follow the
same procedures detailed in the previous section for General
The tests performed by the Advanced Diagnostics diskette are far more
detailed and precise than those of the general Diagnostics diskette in
the GTO. In addition to identifying the problem component, the
Advanced Diagnostics further attempt to identify the specific part of
the device that is malfunctioning.
Once a problem is identified, the HMS provides detailed instructions to
perform adjustments, preventive maintenance, removal and replacement of
the effected part. To this end, comprehensive hardware and design
information is available, including parts lists that specify
replacement parts numbers, and internal design specifications.
Table 1. Listing of IBM PC Diagnostic Error Codes
All personal computer error codes for the Power-On Self Test, general
Diagnostics, and Advanced Diagnostics are represented with the device
number followed by two digits other than 00. The device number plus 00
indicates successful completion of the test. This listing is a
compilation from various sources, including USENET's Info-IBMPC Digest,
IBM Technical Reference Manuals, and IBM Hardware, Maintenance and
01x Undetermined problem errors.
02x Power supply errors.
1xx System board errors.
101 System board error - Interrupt failure.
102 System board error - Timer failure.
103 System board error - Timer interrupt failure.
104 System board error - Protected mode failure.
105 System board error - Last 8042 command not accepted.
106 System board error - Converting logic test.
107 System board error - Hot NMI test.
108 System board error - Timer bus test.
109 Direct memory access test error.
121 Unexpected hardware interrupts occurred.
131 Cassette wrap test failed.
161 System Options Error-(Run SETUP) [Battery failure].
162 System options not set correctly-(Run SETUP).
163 Time and date not set-(Run SETUP).
164 Memory size error-(Run SETUP).
199 User indicated configuration not correct.
2xx Memory (RAM) errors.
201 Memory test failed.
202 Memory address error.
203 Memory address error.
3xx Keyboard errors.
301 Keyboard did not respond to software reset correctly or a
stuck key failure was detected. If a stuck key was detected,
the scan code for the key is displayed in hexadecimal. For
example, the error code 49 301 indicates that key 73, the PgUp
key has failed (49 Hex = 73 decimal).
302 User indicated error from the keyboard test or AT system unit
keylock is locked.
303 Keyboard or system unit error.
304 Keyboard or system unit error; CMOS does not match system.
4xx Monochrome monitor errors.
401 Monochrome memory test, horizontal sync frequency test, or
video test failed.
408 User indicated display attributes failure.
416 User indicated character set failure.
424 User indicated 80X25 mode failure.
432 Parallel port test failed (monochrome adapter).
5xx Color monitor errors.
501 Color memory test failed, horizontal sync frequency
test, or video test failed.
508 User indicated display attribute failure.
516 User indicated character set failure.
524 User indicated 80X25 mode failure.
532 User indicated 40X25 mode failure.
540 User indicated 320X200 graphics mode failure.
548 User indicated 640X200 graphics mode failure.
6xx Diskette drive errors.
601 Diskette power on diagnostics test failed.
602 Diskette test failed; boot record is not valid.
606 Diskette verify function failed.
607 Write protected diskette.
608 Bad command diskette status returned.
610 Diskette initialization failed.
611 Timeout - diskette status returned.
612 Bad NEC - diskette status returned.
613 Bad DMA - diskette status returned.
621 Bad seek - diskette status returned.
622 Bad CRC - diskette status returned.
623 Record not found - diskette status returned.
624 Bad address mark - diskette status returned.
625 Bad NEC seek - diskette status returned.
626 Diskette data compare error.
7xx 8087 or 80287 math coprocessor errors.
9xx Parallel printer adapter errors.
901 Parallel printer adapter test failed.
10xx Reserved for parallel printer adapter.
11xx Asynchronous communications adapter errors.
1101 Asynchronous communications adapter test failed.
12xx Alternate asynchronous communications adapter errors.
1201 Alternate asynchronous communications adapter test failed.
13xx Game control adapter errors.
1301 Game control adapter test failed.
1302 Joystick test failed.
14xx Printer errors.
1401 Printer test failed.
1404 Matrix printer failed.
15xx Synchronous data link control (SDLC) communications adapter
1510 8255 port B failure.
1511 8255 port A failure.
1512 8255 port C failure.
1513 8253 timer 1 did not reach terminal count.
1514 8253 timer 1 stuck on.
1515 8253 timer 0 did not reach terminal count.
1516 8253 timer 0 stuck on.
1517 8253 timer 2 did not reach terminal count.
1518 8253 timer 2 stuck on.
1519 8273 port B error.
1520 8273 port A error.
1521 8273 command/read timeout.
1522 Interrupt level 4 failure.
1523 Ring Indicate stuck on.
1524 Receive clock stuck on.
1525 Transmit clock stuck on.
1526 Test indicate stuck on.
1527 Ring indicate not on.
1528 Receive clock not on.
1529 Transmit clock not on.
1530 Test indicate not on.
1531 Data set ready not on.
1532 Carrier detect not on.
1533 Clear to send not on.
1534 Data set ready stuck on.
1536 Clear to send stuck on.
1537 Level 3 interrupt failure.
1538 Receive interrupt results error.
1539 Wrap data miscompare.
1540 DMA channel 1 error.
1541 DMA channel 1 error.
1542 Error in 8273 error checking or status reporting.
1547 Stray interrupt level 4.
1548 Stray interrupt level 3.
1549 Interrupt presentation sequence timeout.
16xx Display emulation errors (327x, 5520, 525x).
17xx Fixed disk errors.
1701 Fixed disk POST error.
1702 Fixed disk adapter error.
1703 Fixed disk drive error.
1704 Fixed disk adapter or drive error.
1780 Fixed disk 0 failure.
1781 Fixed disk 1 failure.
1782 Fixed disk controller failure.
1790 Fixed disk 0 error.
1791 Fixed disk 1 error.
18xx I/O expansion unit errors.
1801 I/O expansion unit POST error.
1810 Enable/Disable failure.
1811 Extender card warp test failed (disabled).
1812 High order address lines failure (disabled).
1813 Wait state failure (disabled).
1814 Enable/Disable could not be set on.
1815 Wait state failure (disabled).
1816 Extender card warp test failed (enabled).
1817 High order address lines failure (enabled).
1818 Disable not functioning.
1819 Wait request switch not set correctly.
1820 Receiver card wrap test failure.
1821 Receiver high order address lines failure.
19xx 3270 PC attachment card errors.
20xx Binary synchronous communications (BSC) adapter errors.
2010 8255 port A failure.
2011 8255 port B failure.
2012 8255 port C failure.
2013 8253 timer 1 did not reach terminal count.
2014 8253 timer 1 stuck on.
2016 8253 timer 2 did not reach terminal count or timer 2 stuck on.
2017 8251 Data set ready failed to come on.
2018 8251 Clear to send not sensed.
2019 8251 Data set ready stuck on.
2020 8251 Clear to send stuck on.
2021 8251 hardware reset failed.
2022 8251 software reset failed.
2023 8251 software "error reset" failed.
2024 8251 transmit ready did not come on.
2025 8251 receive ready did not come on.
2026 8251 could not force "overrun" error status.
2027 Interrupt failure - no timer interrupt.
2028 Interrupt failure - transmit, replace card or planar.
2029 Interrupt failure - transmit, replace card.
2030 Interrupt failure - receive, replace card or planar.
2031 Interrupt failure - receive, replace card.
2033 Ring indicate stuck on.
2034 Receive clock stuck on.
2035 Transmit clock stuck on.
2036 Test indicate stuck on.
2037 Ring indicate stuck on.
2038 Receive clock not on.
2039 Transmit clock not on.
2040 Test indicate not on.
2041 Data set ready not on.
2042 Carrier detect not on.
2043 Clear to send not on.
2044 Data set ready stuck on.
2045 Carrier detect stuck on.
2046 Clear to send stuck on.
2047 Unexpected transmit interrupt.
2048 Unexpected receive interrupt.
2049 Transmit data did not equal receive data.
2050 8251 detected overrun error.
2051 Lost data set ready during data wrap.
2052 Receive timeout during data wrap.
21xx Alternate binary synchronous communications adapter errors.
2110 8255 port A failure.
2111 8255 port B failure.
2112 8255 port C failure.
2113 8253 timer 1 did not reach terminal count.
2114 8253 timer 1 stuck on.
2115 8253 timer 2 did not reach terminal count or timer 2 stuck on.
2116 8251 Data set ready failed to come on.
2117 8251 Clear to send not sensed.
2118 8251 Data set ready stuck on.
2119 8251 Clear to send stuck on.
2120 8251 hardware reset failed.
2121 8251 software reset failed.
2122 8251 software "error reset" failed.
2123 8251 transmit ready did not come on.
2124 8251 receive ready did not come on.
2125 8251 could not force "overrun" error status.
2126 Interrupt failure - no timer interrupt.
2128 Interrupt failure - transmit, replace card or planar.
2129 Interrupt failure - transmit, replace card.
2130 Interrupt failure - receive, replace card or planar.
2131 Interrupt failure - receive, replace card.
2133 Ring indicate stuck on.
2134 Receive clock stuck on.
2135 Transmit clock stuck on.
2136 Test indicate stuck on.
2137 Ring indicate stuck on.
2138 Receive clock not on.
2139 Transmit clock not on.
2140 Test indicate not on.
2141 Data set ready not on.
2142 Carrier detect not on.
2143 Clear to send not on.
2144 Data set ready stuck on.
2145 Carrier detect stuck on.
2146 Clear to send stuck on.
2147 Unexpected transmit interrupt.
2148 Unexpected receive interrupt.
2149 Transmit data did not equal receive data.
2150 8251 detected overrun error.
2151 Lost data set ready during data wrap.
2152 Receive timeout during data wrap.
22xx Cluster adapter errors.
24xx Enhanced graphics adapter errors.
29xx Color matrix printer errors.
33xx Compact printer errors.