Allen-Bradley · PLC and HMI modules
1756-DHRIO — ControlLogix DH+ / Remote I/O communication module: fault codes, repair & supply
The 1756-DHRIO is a ControlLogix communication module that connects a ControlLogix chassis to Data Highway Plus (DH+) or Remote I/O networks. It is commonly found on older plants that still run PLC-5 or SLC 500 devices. Star Automations sources and supplies the 1756-DHRIO and repairs failed units at component level, so you can choose between a replacement and getting your existing unit restored. This is a discontinued OEM line. We source it from global surplus, and advance payment secures your delivery slot. Most quotes come back the same day — send the part number or the fault code on WhatsApp.
Common 1756-DHRIO fault codes and what we usually find
Fault code wording can differ by firmware and manual revision — always confirm against the manual for your exact unit. The causes below are typical findings, not a diagnosis of your specific unit.
| Code | Meaning | Typical cause |
|---|---|---|
| OK LED red | Module fault | Hardware or firmware fault, chassis seating problem |
| Channel A or B LED off | No network activity | Cable break, missing termination, wrong channel configuration |
| Channel LED flashing red | Network error | Duplicate node address, baud rate mismatch, noisy or damaged cable |
| Display shows no node address | Module not configured | Channel not set to DH+ or Remote I/O in the module configuration |
When a 1756-DHRIO needs attention
- PLC-5 or SLC 500 stations not visible from the ControlLogix
- DH+ messages timing out
- Remote I/O adapter drops in and out
- Module OK LED red or flashing
- Intermittent communication on a long DH+ trunk
Replace or repair your 1756-DHRIO
Source a replacement
Send the part number. We check sourcing from global surplus and the OEM channel and reply the same day with availability, condition and price. Advance or verified escrow applies.
Repair your existing unit
If sourcing takes longer or you want to keep your configuration, we repair at component level — power stage, gate-drive, control and supply sections — and test before dispatch.
What people look up for the 1756-DHRIO
- 1756-DHRIO repair
- 1756-DHRIO replacement
- 1756-DHRIO obsolete alternative
- DH+ to EtherNet/IP migration
- 1756-DHRIO duplicate node address
- ControlLogix DH+ module not communicating
1756-DHRIO — common questions
Can you supply the 1756-DHRIO in India?
Can a faulty 1756-DHRIO be repaired instead of replaced?
My 1756-DHRIO shows OK LED red (module fault). What should I do?
Is the exact part number important?
Need the 1756-DHRIO now?
Send the part number or fault code — we reply the same day. Serving Chennai, Puducherry, Bengaluru, Hyderabad, Delhi and pan-India.