CJ1M-CPU13-ETN ERR/ALM LED Solid Red: Field Troubleshooting Guide

The CJ1M-CPU13-ETN is a compact SYSMAC CJ-series CPU unit with built-in 100Base-TX Ethernet and on-board serial ports. When the front-panel ERR/ALM LED latches solid red and CX-Programmer cannot establish a Toolbus, SYSMAC WAY, or Ethernet (FINS/TCP) session, the controller has entered a fatal CPU fault state. This reference walks through the diagnostics, recovery attempts, port verification, and replacement decisions used when a CJ1M CPU13-ETN refuses all communications.

1. Problem Summary

Reported symptom on a bench-top CJ1M-CPU13-ETN:

• Power applied; RUN LED off, ERR/ALM LED solid red (non-blinking).
• CX-Programmer Auto-Online times out on Toolbus to the peripheral port.
• CX-Programmer Auto-Online times out on Ethernet (FINS/TCP, port 9600).
• Replacing the unit with a CJ1M-CPU22 (no ETN) restores all communications after the I/O table is recompiled with a Dummy CPU Bus Unit slot for the missing ETN.

This is a classic fatal-stop pattern: a non-recoverable hardware fault inside the CPU module that prevents even low-level Toolbus handshaking on the peripheral port.

2. Affected Hardware and Revisions

Refer to the official CJ1M-CPU1@-ETN datasheet (PDF) for the 90 × 65 mm (H × D) compact form factor, 100Base-TX specifications, and supported instruction set. The CJ1M series itself was announced for discontinuation with the recommended migration path being the CJ2M series.

3. Front-Panel LED Meanings

A solid ERR/ALM LED is the visual signature of a fatal PLC error (error code typically in A401 status bits). The on-board ETN unit is rendered inoperative while the fault is latched, so no FINS/TCP, Socket, or HTTP service will be available from CX-Programmer or any SCADA client.

4. Root-Cause Classification

Fatal-stop causes documented for the CJ1M platform fall into four classes. Run the diagnostic flow before assuming hardware failure.

4.1 Memory / program fault

• UM (User Memory) checksum error (A401.15 set after power-up)
• I/O table verification error (A401.10 / A401.11)
• Too many expansion racks or I/O points exceeded
• Invalid task number reference in scheduled interrupt task

4.2 Scan-time fault

• Cycle time exceeded the Maximum Cycle Time set in PLC Setup
• Watchdog timer (WDT) overflow — typically >1 s of consecutive overrun

4.3 Power-supply / hardware fault

• Insufficient 5 VDC from the CJ1W-PA202 / PD022 power supply to the CPU
• Internal CPU module failure (this case)
• Corrupt flash/UM storage on the CPU

4.4 Add-on / bus fault

• CPU Bus Unit (e.g., ETN) recognition error
• I/O table mismatch between programmed and physical configuration

5. Pre-Replacement Diagnostic Procedure

Before concluding "bad PLC", exhaust the recoverable paths. Reference: CJ1M CPU Units with Ethernet Functions Operation Manual (W441-E1-03, PDF).

1. Power cycle the complete rack. Power OFF for at least 10 seconds, restore power, watch the LED sequence. A normal CJ1M-CPU13-ETN powers up with RUN OFF → COMM/PRPHL test blink → RUN green, ERR/ALM off. Anything other than this on a virgin unit is a fault signal.
2. Verify the power supply is a genuine Omron CJ1W-PA202 or PD022 with adequate 5 VDC current budget for the CPU plus any Special I/O Units. Check the PSU output with a DMM under load.
3. Confirm CX-Programmer device type. When CX-Programmer opens the Change PLC dialog, select device type CPU11/12/13 for the ETN family, or CPU21/22/23 for non-ETN. The online connection can fail if the wrong device type is forced.
4. Try all three physical paths:
   • Peripheral port (4-pin mini-DIN on the left side of the CPU) → XW2Z-200S-CV / -500S-CV cable → PC USB-serial adapter.
   • RS-232C port (DB-9 on the bottom face) → standard straight-through serial cable, default SYSMAC WAY parameters.
   • Ethernet 100Base-TX on the ETN → default IP 192.168.250.1 / node 1 / network 0.
5. Force default communications via the CPU DIP switches (see section 6).
6. Capture the error log if CX-Programmer can briefly handshake. The PLC Error Log dialog shows the most recent fatal codes (e.g., 0x80F0 = cycle time over, 0x80F1 = I/O bus error).
7. Try a known-good substitute CPU on the same rack. If a CJ1M-CPU22 runs cleanly with a Dummy CPU Bus Unit for the ETN, the CPU13-ETN is proven defective.

6. DIP Switch Configuration for Default Communications

The CJ1M CPU has an 8-position DIP switch on the front face. On a new unit these are normally all OFF, but a previous integrator may have changed them. Force defaults to eliminate configuration as a fault source.

Recommended recovery state: set SW5 = ON so the RS-232C port reverts to its hardware default, which is the SYSMAC WAY protocol on the following parameters:

• Baud: 9600 bps
• Data bits: 7
• Parity: Even
• Stop bits: 2
• Start bits: 1
• Unit number: 0

With SW5 = ON, CX-Programmer can Auto-Online regardless of any corrupt PLC Setup values that may have been written to the project.

7. Connection Parameter Reference

Match the CX-Programmer Network Type dropdown to the port you are probing.

8. I/O Table Workaround for a Substitute CPU

When substituting a CJ1M-CPU22 (no ETN) for a CJ1M-CPU13-ETN to keep the system online, CX-Programmer will reject the existing I/O table because the ETN slot is physically empty. Insert a dummy CPU Bus Unit so the verification passes:

1. Open the project, double-click I/O Table in the project tree.
2. Select the empty slot where the ETN was registered.
3. Right-click → Add Unit → choose any Special I/O Unit or CPU Bus Unit that the slot is wired for, or use the Create/Unverified option to create a placeholder.
4. Transfer the modified I/O table to the new CPU.
5. Cycle power and confirm ERR/ALM stays off.

9. Resolution Path

After exhausting section 5 without restoring comms and confirming a substitute CPU works on the same rack, treat the CJ1M-CPU13-ETN as failed-in-field hardware and execute the following:

1. Capture the unit's serial number, lot code, and firmware ID via the rear label.
2. Open a warranty / RMA case with the original vendor. The CJ1M-CPU13-ETN ships with a five-year warranty from most authorized Omron distributors.
3. Order a verified replacement; if the application is ethernet-light, a CJ1M-CPU12-ETN or CJ1M-CPU11-ETN is pin- and firmware-compatible (only the UM program capacity differs).
4. For new installations, evaluate the CJ2M-CPU3@ series as the recommended migration target per the CJ1M discontinuation notice. CJ2M supports the same ladder and ST instruction set with the same I/O, but uses a different CPU Bus Unit address map; consult the CJ2M migration guide before reusing the project file.

10. Verification Checklist

After installing the replacement CPU13-ETN, confirm normal operation:

• Power-on LED sequence: RUN green, ERR/ALM off, LINK green, COMM/PRPHL test blink.
• CX-Programmer Auto-Online completes on Toolbus (peripheral port).
• CX-Programmer Auto-Online completes on SYSMAC WAY (RS-232C, 9600/7/E/2).
• Ping the ETN default IP 192.168.250.1 from a workstation on the same subnet.
• CX-Programmer FINS/TCP connection established to node 1, network 0, unit 0.
• I/O Table Verification completes with no errors.
• PLC Error Log is empty (no fatal or non-fatal entries).

11. Troubleshooting Matrix

12. Common Pitfalls

• Assuming the ETN LED side is the failure — a solid ERR/ALM disables the ETN at the CPU bus level; the ETN hardware may be fine.
• Forgetting the I/O table rebuild when swapping a CJ1M-CPU13-ETN for a non-ETN substitute (or vice versa). The I/O table error will re-latch ERR/ALM.
• Leaving SW1 = ON (write-protect) on a fresh unit, which prevents any new project from being transferred.
• Using a third-party USB-to-serial adapter that does not assert the +5 V pin on the peripheral-port cable. Use the Omron XW2Z-200S-CV or XW2Z-500S-CV cable.
• Forgetting that the CJ1M series is end-of-life; if the application is greenfield, design on CJ2M from the start.