输人输出是PLC与外部设备进行信息交流的通道，其是否正常工作，除了和输入输出单元有关外，还与联接配线、接线端子、保险丝等元件状态有关。
出现输入故障时，首先检查LED电源指示器是否响应现场元件（如按钮、行程开关等）。如果输入器件被激励（即现场元件已动作），而指示器不亮，则下一步就应检查输入端子的端电压是否达到正确的电压值。若电压值正确，则可替换输入模块。若一个LED逻辑指示器变暗，而且根据编程器件监视器、处理器未识别输入，则输入模块可能存在故障。如果替换的模块并未解决问题且连接正确，则可能是机架或通信电缆出了问题。
出现输出故障时，首先应察看输出设备是否响应LED状态指示器。若输出触点通电，模块指示器变亮，输出设备不响应。那么，首先应检查保险丝或替换模块。若保险丝完好，替换的模块未能解决问题，则应检查现场接线。若根据编程设备监视器显示一个输出器被命令接通，但指示器关闭，则应替换模块。
Cat Lift Truck Forktruck Valve Lockoff
Parker KIT SERV=DV35-SPL-13
Allen Bradley Error Correcting RAM Memory Board, 1775-MS4,
Dorma PT40 PT-40 700-SS
Kubler HC77/s1 Hour Meter/Shot Counter Battenfeld 02000MA482 24 VDC
Mitsubishi PC Board, AFHA-03-DWC, BY171E466G51, Rev C,
30 day Honeywell PCB Data Freeway Controller
Braden Excel XF-1 110917 Filter Qty Available
OEM Genuine Kyocera KM-C830 370AA011001 Black Toner Cartridge
HP HP3005-KIT-REF SEALED
General Electric CR120B04222 Relay GE 120 VAC Coil, 10 Amp Free Shipping!
Setra Pressure Transducer 225 225110CPGC42B06 SEALED
Suhner MONOmaster Automatic Drill Unit w/ 1 HP ABB AC Drive Motor,
Fanuc Servo Amplifier, A06B-6058-H324, A16B / 08A,
Control Techniques Dinverter 2.5 HP Drive, Type DINB,
Yaskawa DI-101 EZZ020642A UTC000450 Logic Interface A1000 Drive
Agastat Model 7012EK with 30 Day Warranty
Parker PK802HLL06 Piston Seal Kit
Fanuc AC Spindle Servo Unit, # A06B-6044-H032, A20B / 24J,
ESW Electronic Systems Of Wisconsin rev B PCB Board
OEM Genuine Lanier 884913 Yellow Toner Cartridge LD228c/LD232c
Flex-Core CTL-1000HT Current Transducer Amperes: 1000
Siemens EWSD S30810-Q1330-XX-5/01 Module
Shibaura VMC Circuit Board, # H ,
Fanuc Model 20M DC Servo Motor, A06B-0652-B005 #0003 (0),
OEM Pitney Bowes Oce 469-3 Yellow Imaging Unit
Medar for Allen Bradley Module
Cisco WS-C2950SX-24 Catalyst Switch
Emerson PCM-19 Merge Conveyor Controller Free Shipping!
Dorma PT40 PT-40 700-SS
Sodick FS-A5C CNC EDM PC Board, P.MOS-001E WKH, Mark VII Controller,
Mitsubishi Numerical Control System, FCA65M, H/W FCU6-MU021,
Mitsubishi AC Servo Motor, # HA80CB-SS, w/ Encoder,
Fanuc Velocity Control Unit, # A06B-6047-H004, w/ A20B / 05B,
Hansen EZE/L2 Cartridge Relief Valve 1", 185 PSIG for Refrigerant Gas
Inland / Kollmorgen DC Servo Motor, TT B, TT 4207,
Used Preco Robot Interconnect Card B A
ABB Robotics S3 Robot Teach Pendant, 3HAB 3HAB