Mitsubishi · PLC and HMI modules
Q03UDECPU — MELSEC-Q Q03UDECPU: fault codes, repair & supply
The Q03UDECPU is a Mitsubishi MELSEC-Q series universal model CPU with built-in Ethernet. Star Automations sources and supplies the Q03UDECPU 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 MELSEC Q CPU 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 |
|---|---|---|
| ERR (red) | Self-diagnostic error | Read the error code in GX Works |
| RUN (off) | CPU stopped | Stop switch, stop error or program stop |
| BAT (yellow) | Battery low | Replace the battery |
| USER | Annunciator on | User-programmed fault flag active |
When a Q03UDECPU needs attention
- CPU will not go to RUN
- ERR LED on
- Battery alarm
- Ethernet communication problems
- Module recognition errors on the base unit
Replace or repair your Q03UDECPU
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.
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Q03UDECPU — common questions
Can you supply the Q03UDECPU in India?
Can a faulty Q03UDECPU be repaired instead of replaced?
My Q03UDECPU shows ERR (red) (self-diagnostic error). What should I do?
Is the exact part number important?
Need the Q03UDECPU now?
Send the part number or fault code — we reply the same day. Serving Chennai, Puducherry, Bengaluru, Hyderabad, Delhi and pan-India.